No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
The first human settlement of the New World: A closer look at craniofacial variation and evolution of early and late Holocene Native American groups
Abstract
During its expansion across the globe, Homo sapiens successfully survived to major adaptive challenges as a species, inviting scientific research to plunge into the particularities of continental settlement dynamics. A recurrent paleoanthropological concern is about the understanding of the great deal of craniofacial diversity that evolved into the Americas, which includes a vector of continuum variation between a generalized morphology observed among humans groups leading the Out-of-Africa dispersion, and a derived set of craniofacial traits classically labeled as "mongoloid" and that would have arise in Asia during the Holocene. Here, we use geometric morphometric techniques and multivariate statistics along with quantitative genetic approaches to look more closely into the human craniofacial evolutionary history during the Late Pleistocene-Early Holocene from Asia and the New World. We detected significant signals of deviation of the neutral evolutionary expectations, suggesting an important action of non-stochastic evolution (e.g. natural selection, phenotypic plasticity) in the Americas. We also found further support to the Recurrent Gene Flow model that refers to an ancestral, founder population experiencing a standstill in Beringia, and exhibiting high within-group craniofacial variation. This original, internally variable stock would have been the ancestral source of variation that fuelled the subsequent local micro evolution of other derived phenotypic patterns, giving origin to the craniofacial diversity observed among Holocene Native American samples.
... Significant advances in the last few decades have been achieved thanks to several interdisciplinary attempts that provided comprehensive explanations 4-10 , the application of cutting-edge methods that allowed the capture of a larger amount of morphological information [11][12][13][14][15][16] , and the extraction, amplification, and sequencing of aDNA 17 . Some aspects of the expanding evolutionary process, such as the magnitude of biological variation that characterized the earliest inhabitants have become a relevant matter of discussion, especially in relation to the South American archaeological record 2,7,[11][12][13][14][15][18][19][20][21] . While some authors have characterized the first Americans arriving in the continent as highly morphologically heterogeneous (i.e., large differences among individuals within a population), others described them as being mostly homogeneous (i.e., strong similarities among individuals) 16,18,[20][21][22][23] . ...
... Some aspects of the expanding evolutionary process, such as the magnitude of biological variation that characterized the earliest inhabitants have become a relevant matter of discussion, especially in relation to the South American archaeological record 2,7,[11][12][13][14][15][18][19][20][21] . While some authors have characterized the first Americans arriving in the continent as highly morphologically heterogeneous (i.e., large differences among individuals within a population), others described them as being mostly homogeneous (i.e., strong similarities among individuals) 16,18,[20][21][22][23] . Understanding the degree of variation amongst these groups/individuals has implications for the models that can be proposed since it provides clues of the population size of the first migrants and/or the number of consecutive migrations by which humans arrived in the continent 11,18,19,[21][22][23] . ...
... Understanding the degree of variation amongst these groups/individuals has implications for the models that can be proposed since it provides clues of the population size of the first migrants and/or the number of consecutive migrations by which humans arrived in the continent 11,18,19,[21][22][23] . Another unanswered question in relation to the biological diversity of humans in the continent is whether the morphological changes that have been described across time represent different ancestral lineages outside America or are the result of local evolution 1,2,5,7,[12][13][14][15][16][18][19][20] . ...
The biological variation of the earliest skeletons of South America has been intensely debated for the last two centuries. One of the major research constraints has been the limited number of available samples dating to the early Holocene. We here present the first direct radiocarbon-date for the early Holocene human skeleton from Toca dos Coqueiros (Serra da Capivara, Brazil), also known as “Zuzu” (8,640+30 BP; 9,526-9,681 cal years BP). We performed craniometric analyses using exclusively samples from Brazil, to revisit the sex of the skeleton, and to discuss the evolutionary processes involved in the occupation of the continent. The sex of the individual was estimated as a female when compared to late and early Holocene individuals, but as a male when compared only to the early Holocene series. We also found that Zuzu presents the strongest differences with the late Holocene Guajajara individuals, located nearby, and the strongest similarities with the early Holocene series from Lagoa Santa, attesting for solid biological affinities among early Holocene individuals from Brazil, as well as a moderate level of morphological variation among them. This suggests that the early individuals were part of the same heterogeneous lineage, possibly a different one from which late Holocene populations diverged.
... Significant advances in the last few decades have been achieved thanks to several interdisciplinary attempts that provided comprehensive explanations 4-10 , the application of cutting-edge methods that allowed the capture of a larger amount of morphological information [11][12][13][14][15][16] , and the extraction, amplification, and sequencing of aDNA 17 . Some aspects of the expanding evolutionary process, such as the magnitude of biological variation that characterized the earliest inhabitants have become a relevant matter of discussion, especially in relation to the South American archaeological record 2,7,[11][12][13][14][15][18][19][20][21] . While some authors have characterized the first Americans arriving in the continent as highly morphologically heterogeneous (i.e., large differences among individuals within a population), others described them as being mostly homogeneous (i.e., strong similarities among individuals) 16,18,[20][21][22][23] . ...
... Some aspects of the expanding evolutionary process, such as the magnitude of biological variation that characterized the earliest inhabitants have become a relevant matter of discussion, especially in relation to the South American archaeological record 2,7,[11][12][13][14][15][18][19][20][21] . While some authors have characterized the first Americans arriving in the continent as highly morphologically heterogeneous (i.e., large differences among individuals within a population), others described them as being mostly homogeneous (i.e., strong similarities among individuals) 16,18,[20][21][22][23] . Understanding the degree of variation amongst these groups/individuals has implications for the models that can be proposed since it provides clues of the population size of the first migrants and/or the number of consecutive migrations by which humans arrived in the continent 11,18,19,[21][22][23] . ...
... Understanding the degree of variation amongst these groups/individuals has implications for the models that can be proposed since it provides clues of the population size of the first migrants and/or the number of consecutive migrations by which humans arrived in the continent 11,18,19,[21][22][23] . Another unanswered question in relation to the biological diversity of humans in the continent is whether the morphological changes that have been described across time represent different ancestral lineages outside America or are the result of local evolution 1,2,5,7,[12][13][14][15][16][18][19][20] . ...
The biological variation of the earliest skeletons of South America has been intensely debated for the last two centuries. One of the major research constraints has been the limited number of available samples dating to the early Holocene. We here present the first direct radiocarbon-date for the early Holocene human skeleton from Toca dos Coqueiros (Serra da Capivara, Brazil), also known as “Zuzu” (8,640+30 BP; 9,526-9,681 cal years BP). We performed craniometric analyses using exclusively samples from Brazil, in order to revisit the sex of the skeleton, and to discuss the evolutionary processes involved in the occupation of the continent. The sex of the individual was estimated as a female when compared to late and early Holocene individuals, but as a male when compared only to the early Holocene series. We also found that Zuzu presents the strongest differences with the late Holocene Guajajara individuals, located nearby, and the strongest similarities with the early Holocene series from Lagoa Santa, attesting for solid biological affinities among early Holocene individuals from Brazil, as well as a moderate level of morphological variation among them. This suggests that the early individuals were part of the same heterogeneous lineage, possibly a different one from which late Holocene populations diverged.
... Weaver et al. 2007;Mutumi et al. 2016;Maluleke et al. 2017) but evidence for drift is gradually accumulating (e.g. Cheverud 2002, 2004;Weaver et al. 2007;Betti et al. 2010;Smith 2011;de Azevedo et al. 2015). Surprisingly, few studies have attempted to consider the relative roles of drift and selection on phenotypic divergence within the same system. ...
... Although the most direct evidence for random genetic drift could be obtained using genetic approaches (Lande 1976;Leinonen et al. 2008;Rogell et al. 2010;Sun et al. 2013), drift should also be evident in the phenotypes of species. Several methods have been developed to test for selection within phenotypic variation against the null model of drift, for example, the rate test (Turelli 1988) and an adaptation of Lande's (1976) quantitative genetic model Cheverud 2002, 2004;de Azevedo et al. 2015;Mutumi et al. 2017). ...
... We used Lande's model (Lande 1976) to assess the relative contributions of drift and selection to geographic phenotypic variation in the two species. Lande's model is based on quantitative theory of molecular evolution but has been adapted for use on phenotypic traits Cheverud 2002, 2004;de Azevedo et al. 2015;Smith 2011). The theory uses drift as a null model for phenotypic variation. ...
Acoustic signals mediate important functions, e.g. orientation, foraging and communication, that impact on the survival and reproduction of animals. The propagation of acoustic signals is also known to be influenced by habitat, particularly differences in climate. It is therefore likely that the environment would exert significant influence on such signals and that selection rather than drift would be largely responsible for geographic variation in acoustic signals. We investigated the role of selection and drift in geographic variation in the echolocation of two species of horseshoe bats Rhinolophus damarensis and R. clivosus (Rhinolophidae) with wide geographic distributions across the arid and mesic biomes of southern Africa. In both species, selection was found to be the dominant evolutionary process influencing phenotypic variation; however, there was evidence of drift in R. clivosus. Furthermore, selection was not differentially exerted across populations because there was no change in the results when localities were excluded one at a time. Population divergence appeared to be mediated by selection on traits associated with manoeuvrability, detection and size in both species despite their disparate distributions. However, the climatic factor that best explained geographic variation in echolocation was dependent on the biomes occupied by the species. Temperature was the dominant climatic factor in R. damarensis, a species with a largely arid distribution. In R. clivosus, a species with distributions across both mesic and arid biomes, temperature and relative humidity together explained variation in echolocation.
... Nevertheless, evidence for the role of drift has accumulated (Ackermann & Cheverud, 2002de Azevedo, Quinto-Sánchez, Paschetta, & González-José, 2015;Lande, 1976;Smith, 2011;Weaver et al., 2007) and many studies have explored various methods to determine the relative contributions of adaptation and drift, for example, the rate test (Turelli, 1988), genetic approaches (Leinonen, O'Hara, Cano, & Merilä, 2008;Rogell, Eklund, Thörngren, Laurila, & Höglund, 2010;Sun et al., 2013), and quantitative genetic models (Ackermann & Cheverud, 2002de Azevedo et al., 2015;Lande, 1976). ...
... Nevertheless, evidence for the role of drift has accumulated (Ackermann & Cheverud, 2002de Azevedo, Quinto-Sánchez, Paschetta, & González-José, 2015;Lande, 1976;Smith, 2011;Weaver et al., 2007) and many studies have explored various methods to determine the relative contributions of adaptation and drift, for example, the rate test (Turelli, 1988), genetic approaches (Leinonen, O'Hara, Cano, & Merilä, 2008;Rogell, Eklund, Thörngren, Laurila, & Höglund, 2010;Sun et al., 2013), and quantitative genetic models (Ackermann & Cheverud, 2002de Azevedo et al., 2015;Lande, 1976). ...
... The quantitative theory of genetic evolution as described by the Lande's model (Lande, 1976) has been applied to assess whether random evolutionary processes alone can explain phenotypic divergence (Ackermann & Cheverud, 2002de Azevedo et al., 2015;Smith, 2011). The theory postulates a null model of drift, the rejection of which suggests that selection can be inferred (Smith, 2011). ...
Natural selection and drift can act on populations individually, simultaneously or in tandem and our understanding of phenotypic divergence depends on our ability to recognize the contribution of each. According to the quantitative theory of evolution, if an organism has diversified through neutral evolutionary processes (mutation and drift), variation of phenotypic characteristics between different geographic localities (B) should be directly proportional to the variation within localities (W), that is, B ∝ W. Significant deviations from this null model imply that non-neutral forces such as natural selection are acting on a phenotype. We investigated the relative contributions of drift and selection to intraspecific diversity using southern African horseshoe bats as a test case. We characterized phenotypic diversity across the distributional range of Rhinolophus simulator (n = 101) and Rhinolophus swinnyi (n = 125) using several traits associated with flight and echolocation. Our results suggest that geographic variation in both species was predominantly caused by disruptive natural selection (B was not directly proportional to W). Evidence for correlated selection (co-selection) among traits further confirmed that our results were not compatible with drift. Selection rather than drift is likely the predominant evolutionary process shaping intraspecific variation in traits that strongly impact fitness.
... However, there has been controversy on both the significance of drift to biological diversification and whether or not it can be distinguished from adaptation (Brandon and Carson 1996;Millstein 2002;Brandon 2005). Nevertheless evidence is accumulating for the role of drift (Lande 1976;Ackermann and Cheverud 2002;Weaver et al. 2007;Smith 2011;de Azevedo et al. 2015) and many studies are exploring various methods to account for the relative contributions of adaptation and drift e.g., the rate test (Turelli et al. 1988), genetic approaches (Leinonen et al. 2008;Rogell et al. 2010;Sun et al. 2013), and quantitative genetic models e.g., Lande's model (Lande 1976;Ackermann and Cheverud 2002;Smith 2011;de Azevedo et al. 2015). The Lande's model is easier to apply in this case because it has been adapted by Ackermann and Cheverud (2002) to use phenotypic parameters instead of genetic traits. ...
... However, there has been controversy on both the significance of drift to biological diversification and whether or not it can be distinguished from adaptation (Brandon and Carson 1996;Millstein 2002;Brandon 2005). Nevertheless evidence is accumulating for the role of drift (Lande 1976;Ackermann and Cheverud 2002;Weaver et al. 2007;Smith 2011;de Azevedo et al. 2015) and many studies are exploring various methods to account for the relative contributions of adaptation and drift e.g., the rate test (Turelli et al. 1988), genetic approaches (Leinonen et al. 2008;Rogell et al. 2010;Sun et al. 2013), and quantitative genetic models e.g., Lande's model (Lande 1976;Ackermann and Cheverud 2002;Smith 2011;de Azevedo et al. 2015). The Lande's model is easier to apply in this case because it has been adapted by Ackermann and Cheverud (2002) to use phenotypic parameters instead of genetic traits. ...
... The quantitative theory of molecular evolution as described by the Lande's model (Lande 1976) has been applied to show how random evolutionary processes can account for phenotypic divergence (Ackermann and Cheverud 2002;Ackermann and Cheverud 2004;Smith 2011;de Azevedo et al. 2015). The theory gives a null model against which the relative contributions of adaptation and drift can be weighed (Smith 2011). ...
The study of geographic variation and its causes in the phenotypes of animals elucidates how evolutionary processes generate biodiversity. This thesis attempts to uncouple the relative contributions of adaptive and neutral mechanisms to population divergence in African horseshoe bats (genus Rhinolophus). The two species were sampled from their distributional ranges within southern Africa and several morphometric and echolocation parameters were taken. The relative contributions of adaptation and drift were first tested (Chapter 2) using the Lande’s model. It was hypothesised that adaptation would predominate in the diversification of the two horseshoe bats owing to the flight-echolocation and dietecholocation adaptive complexes that intricately tie these two species to environmental conditions. Selection was also hypothesised to be stronger in Rhinolophus swinnyi because it uses higher frequency sound which is more sensitive to atmospheric conditions. The hypotheses were tested using a combination of soft tissue parameters (Chapter 2) and hard tissue parameters (Chapter 3), i.e., 3D scanned skulls analysed using 3D geometric morphometrics. To reconstruct the selective forces, linear mixed-effects models were used to regress climatic variables against echolocation call signals (Chapter 4) based on two hypotheses, the Sensory Drive and the James’ Rule as a guide.
The Lande’s model (Chapter 2 and 3) showed that drift had a minimal effect to the variation of body parameters and echolocation and that selection was stronger on echolocation than on morphometric parameters. Additionally selection was differentially exerted across different localities and between the two species, making the relative roles of selection and drift context specific. Climatic variables (mean annual temperature and relative humidity) were inversely related to the variation in echolocation signals (Chapter 4) within each species. Body size was unrelated to the observed variation, which provided evidence that echolocation signals did not vary as a result of the body size/climate relationship proposed by James’ Rule. Bats rely on both flight and echolocation to survive and reproduce, systems that have to track local habitats closely to perform optimally. Hence selection plays a pivotal role in their diversification.
... Given their importance for understanding New World population history, these skeletal remains have been the subject of numerous cranial morphological assessments in the Americas (e.g., Chatters, 2010;Chatters et al., 2014;Chauchat and Dricot, 1979;Hrdlička, 1928;Hubbe et al., 2015a,b;Jantz and Owsley, 2001;Neves et al., 2003;Neves et al., 2013;Powell, 2005;Reyes et al., 2012;Powell, 1992, 1993). Although Hrdlička initially described Native American populations as homogenous, many recent assessments have demonstrated craniofacial variation among Native American groups (Hrdlička, 1928as cited in Powell, 2005; see also de Azevedo et al., 2015b;Hubbe et al., 2015a;Sardi et al., 2005). Researchers frequently reference two cranial shapes to describe prehistoric Native Americans: one that constitutes a long and narrow (dolichocephalic) shape to generally describe Paleoamericans, and a short and wide (brachycephalic) shape to describe late Holocene populations, respectively. ...
... Recent studies have explained these differences as being derived from populations who shared a common ancestor, but whose cranial forms diverged at some point after the early Holocene (Hubbe et al., 2010; also see de Azevedo et al., 2015b for a discussion). Some researchers have argued that the distinctive vault shapes apparent between the Early and Late periods are the result of evolutionary forces such as genetic drift or selection acting upon these populations (e.g., de Azevedo et al., 2015b;Powell, 2005 andHubbe et al., 2015a for a summary). Although researchers have been addressing these potential explanations for shape differences in South American crania, there are few systematic studies assessing early Holocene cranial variation among western South American populations (but see Manríquez et al., 2011 andMarti andRothhammer, 1987 for exceptions). ...
... Despite new research that has addressed variation using more sophisticated methods from a genetic and phenotypic standpoint, the dolichocephalic and brachycephalic categories and the characteristics (long, narrow or short, wide) associated with these terms are still used to describe early and late Holocene cranial morphology in South America (e.g., de Azevedo et al., 2015b;Fehren-Schmitz et al., 2015;Gonçalves et al., 2013;Kuzminsky, 2013;Manríquez et al., 2011;Perez et al., 2007;Sardi et al., 2005;Scott et al., 2016). The continued use of these terms, dolichocephalic and brachycephalic, to generalize cranial morphology is intriguing given that many researchers today would consider the cranial index too simplistic for assessing cranial variation. ...
South American populations have played a critical role in elucidating the timing, origin, and migration routes of the first Americans. Among the ongoing debates surrounding the peopling of South America, there has been a great deal of focus on the cranial shape of prehistoric populations on this continent, which some researchers have described as having two distinct forms. The cranial shape of early Holocene Paleoamericans, which predate approximately 8000 years BP, has been categorized as dolichocephalic (long-headed), while late Holocene populations have been generally described as brachycephalic (round-headed), despite more recent assessments that examine variation with a higher level of precision. Although more detailed analytical approaches to investigating craniofacial variation are available, researchers still categorize South American crania as having these two head shapes. These distinctions in head shape have been used to infer multiple origin models, some of which contend that the dolichocephalic population was biologically distinct and later replaced by brachycephalic individuals. In contrast, genetic studies infer a common ancestral origin among all prehistoric South American populations. Given discrepancies between genetic and cranial data, our study tests the hypothesis that Holocene populations consist of two cranial morphologies that coincide with the early and late Holocene periods. Using high-resolution 3D models generated from a laser surface scanner, cranial indices for 95 individuals from western South America dating from the Early, Middle, and Late periods were analyzed, most of which have been excluded from cranial assessments in South America. Our results show that the majority of crania analyzed in this study have an intermediate (mesocephalic) head shape, spatiotemporal variability, and no clear transition from dolichocephaly to brachycephaly during the Holocene. By re-examining the relevance of these categories that are determined through the calculation of the cranial index, and general morphological descriptions (long and narrow or short and wide skulls) that coincide with them, our research offers valuable insight into the ongoing debates centered on the colonization of South America. Given our results, we propose that caution should be used when referring to the terms “dolichocephalic” and “brachycephalic” head shapes and the general morphological descriptions for these terms to categorize early and late Holocene South American populations.
... Interestingly, despite the recent expansion of humans into the continent around 16,000 years BP (Prates et al., 2020), several authors have documented high morphological variation in the crania of South Americans from the late Holocene that is even equivalent to the variation observed between populations from different continents (de Azevedo et al., 2017;Gonzlez-José et al., 2001;Hubbe et al., 2011;Hubbe et al., 2015;Menéndez et al., 2015;Paschetta et al., 2010;Sardi et al., 2005). The source of the variability of cranial morphology in South American populations has been broadly discussed, and it is probably associated with several factors including the divergence of more than one ancestral population (Bodner et al., 2012;G omez-Carballa et al., 2018;Neves & Hubbe, 2005;Reich et al., 2012;Ribeiro-dos-Santos et al., 2020;von Cramon-Taubadel et al., 2017;Wang et al., 2007), local evolutionary processes (Delgado et al., 2021;Gonz alez-José et al., 2008;), geographic isolation (Gonz alez-José et al., 2003, and environmental factors such as diet and climate (de Azevedo et al., 2017;Menéndez, 2018;Paschetta et al., 2010;Perez et al., 2011;Perez & Monteiro, 2009). ...
... Interestingly, despite the recent expansion of humans into the continent around 16,000 years BP (Prates et al., 2020), several authors have documented high morphological variation in the crania of South Americans from the late Holocene that is even equivalent to the variation observed between populations from different continents (de Azevedo et al., 2017;Gonzlez-José et al., 2001;Hubbe et al., 2011;Hubbe et al., 2015;Menéndez et al., 2015;Paschetta et al., 2010;Sardi et al., 2005). The source of the variability of cranial morphology in South American populations has been broadly discussed, and it is probably associated with several factors including the divergence of more than one ancestral population (Bodner et al., 2012;G omez-Carballa et al., 2018;Neves & Hubbe, 2005;Reich et al., 2012;Ribeiro-dos-Santos et al., 2020;von Cramon-Taubadel et al., 2017;Wang et al., 2007), local evolutionary processes (Delgado et al., 2021;Gonz alez-José et al., 2008;), geographic isolation (Gonz alez-José et al., 2003, and environmental factors such as diet and climate (de Azevedo et al., 2017;Menéndez, 2018;Paschetta et al., 2010;Perez et al., 2011;Perez & Monteiro, 2009). However, regarding cranial morphology, most studies focus on ectocranial shape variation, while a study of the endocranial variation among South American populations is still missing. ...
Craniovascular traits in the endocranium (traces of middle meningeal vessels and dural venous sinuses, emissary foramina) provide evidence of vascular anatomy in osteological samples. We investigate the craniovascular variation in four South American samples and the effect of artificial cranial modifications (ACM). CT scans of human adult crania from four archeological samples from southern South America (including skulls with ACM) are used for the analyses. The craniovascular features in the four samples are described, skulls with and without ACM are compared, and additionally, South Americans are compared to a previously analyzed sample of Europeans. Of the four South American samples, the Southern Patagonian differs the most, showing the most distinct cranial dimensions, no ACM, and larger diameters of the emissary foramina. Unlike previous studies, we did not find any major differences in craniovascular features between modified and non‐modified skulls, except that the skulls with ACM present somewhat smaller foramina. South Americans significantly differed from Europeans, especially in the anteroposterior dominance of the middle meningeal artery, in the pattern of sinus confluence, in the occurrence of enlarged occipito‐marginal sinuses, and in foramina frequencies and diameters. Craniovascular morphology is not affected by the cranial size, even in skulls with ACM, indicating a minor or null influence of structural topological factors. Concerning the samples from distinct geographic and climatic environments, it must be evaluated whether the craniovascular morphogenesis might be partially influenced by specific functions possibly associated with thermoregulation, intracranial pressure, and the maintenance of intracranial homeostasis.
... De Azevedo et al.'s (2017) study of Indigenous Americans found that the observed craniofacial variation accords with a single ancestral source, supporting the "Beringian standstill" model (Tamm et al. 2007). They also found that the variation accrued since that diverse ancestral population deviates from a neutral evolutionary model, indicating that microevolutionary forces have been at play (de Azevedo et al. 2017). Katz, Grote, and Weaver (2017) explored how the shift from foraging to farming may have influenced human craniofacial form globally. Results showed a modest but significant directional effect between populations that rely on the much softer versus tougher diets (Katz, Grote, and Weaver 2017). ...
... Katz, Grote, and Weaver (2017) explored how the shift from foraging to farming may have influenced human craniofacial form globally. Results showed a modest but significant directional effect between populations that rely on the much softer versus tougher diets (Katz, Grote, and Weaver 2017). Given the Katz, Grote, and Weaver (2017) results, it is quite likely that the diversity of subsistence strategies that Indigenous Americans adopted as they migrated across the Western Hemisphere contributed to the microevolutionary forces inferred by de Azevedo et al. (2017). Considering the vast latitudinal range of the Americas, climate likely played a role, too (Menendez 2018;von Cramon-Taubadel 2014), further obscuring evidence of ancestry. ...
A widely accepted model for the peopling of the Americas postulates a source population in the Northeast Asian maritime region, which includes northern Japan. The model is based on similarities in stone artifacts (stemmed points) found in North American sites dating as early as 15,000 years ago and those of comparable age in Japan and neighboring regions of Northeast Asia. Here we show, on the basis of data and analyses in biological anthropology, that the people who made stemmed points in northern Japan (labeled “Incipient Jomon” in the archaeological literature) represent an unlikely source population for the indigenous peoples of the Western Hemisphere.
... La variación morfológica inter-poblacional de grupos Americanos recientes ha sido descripta como sorprendentemente alta, incluso equivalente a la existente entre poblaciones de distintos continentes (Neves & Hubbe 2005;Sardi et al. 2005;González-José et al. 2008;Hubbe et al. 2015;von Cramon-Taubadel et al. 2017;Ponce de León et al. 2018;Ross & Ubelaker 2019). A pesar de que en las últimas décadas se han ofrecido múltiples explicaciones para comprender dicho patrón morfológico, recientemente se lo ha interpretado como resultado de un proceso de diversificación rápida debido a interacciones entre procesos aleatorios y fundamentalmente adaptaciones a diversos ecosistemas Menéndez 2015;de Azevedo et al. 2017). Sin embargo, aún queda por explicar detalladamente cómo se diferenciaron las poblaciones Sudamericanas en las distintas regiones ecológicas del continente, es decir, cuáles fueron los procesos evolutivos involucrados en la diferenciación poblacional de los grupos nativos americanos a lo largo del Holoceno. ...
... A pesar de esto, es sobresaliente el hecho de que las mayores diferencias se encuentren entre las muestras del Holoceno temprano, y en segundo lugar, entre muestras del Holoceno tardío entre sí, mientras que las diferencias entre muestras del Holoceno temprano/medio y tardío no son considerables. Este resultado brinda apoyo al modelo que plantea que la evolución de las poblaciones humanas de Sudamérica es el resultado de diversos procesos evolutivos rápidos ocurridos in situ y no de distintas oleadas migratorias (Pérez & Monteiro 2009;Menéndez et al. 2014;de Azevedo et al. 2017). ...
El objetivo del presente trabajo es analizar la variación craneométrica en una muestra de individuos del Holoceno temprano/medio al tardío de Perú. Para esto, se registraron 8 medidas lineales en el esqueleto facial y bóveda craneana de 301 individuos procedentes de 19 sitios arqueológicos, los cuales se encuentran ubicados en 4 biomas. Se exploró la variación en la forma y tamaño del cráneo entre individuos de distintos biomas y sitios arqueológicos mediante un Análisis de Componentes Principales y Análisis Discriminante. Complementariamente, se evaluó la afinidad morfológica entre las muestras mediante el cálculo de distancias de Mahalanobis y un análisis de clúster jerárquico de Ward. Asimismo, se estimó el efecto del bioma, sitio arqueológico, altitud, y cronología para explicar el patrón de variación morfológico observado a través de MANOVA. Los resultados mostraron que existen similitudes entre individuos de distintas cronologías, los individuos del Holoceno temprano/medio presentan gran variación morfológica, las muestras mas recientes presentan diferencias en la longitud del cráneo, variables que describen la apertura nasal, pero también el subcomponente alveolar, lo cual a su vez se encuentra asociada a la diversidad de altitud y sitio arqueológico de procedencia. Se discuten los resultados en relación a trabajos previos que estudiaron muestras de Perú, y otras áreas de América del Sur. De esta manera se espera contribuir a la discusión de los debates actuales sobre el poblamiento de Sudamérica, especialmente en torno a las posibles adaptaciones locales.
... El poblamiento Americano ha sido durante décadas un tema de debate cuya discusión continúa hasta hoy en día Powell y Neves, 1999;Goebel et al., 2008;Meltzer, 2009). Particularmente, la variación biológica de las poblaciones americanas fue investigada de manera intensiva durante los últimos ciento cincuenta años (e.g., Lund, 1842;Ameghino, 1909;Turner, 1983;Neves y Pucciarelli, 1991;Bonatto y Salzano, 1997;Moraga et al., 2005;de Saint Pierre et al., 2012;Battaglia et al., 2013;de Azevedo et al., 2015;. Los análisis morfológicos comparativos entre los esqueletos americanos más tempranos y más recientes han sugerido la existencia de un escenario complejo subyacente a la evolución biológica de estas poblaciones. ...
... De esta discusión se desprende que debido a la importancia que podría tener la plasticidad y otros factores locales en la divergencia morfológica, usar sólo análisis morfométricos craneanos resulta insuficiente para apoyar las hipótesis de que las diferencias morfológicas entre muestras americanas tempranas y tardías están relacionadas con procesos migratorios o el modelo de los dos componentes biológicos. En este sentido, si bien actualmente la mayoría de los estudios moleculares sugieren que todas las poblaciones sudamericanas habrían descendido de una misma población ancestral y por tanto, las diferencias morfológicas son el resultado de procesos evolutivos locales (Merriwether et al., 1995;Schurr, 2004;Perego et al., 2009;Reich et al., 2012;de Azevedo et al., 2015;Raghavan et al., 2015;Scott et al., 2016), algunos resultados aislados le dan un soporte relativo al modelo de los dos componentes biológicos (Skoglund et al., 2015). Por lo tanto, aunque la evidencia craneométrica es muy importante para comprender el poblamiento humano y la diversificación en América, estudios y modelos futuros sobre el poblamiento americano basados en este tipo de evidencias deben incorporar mayor cantidad de datos moleculares, morfológicos y arqueológicos en conjunto. ...
Los editores de este libro quieren agradecer a los autores de los capítulos
por su espíritu constructivo a la hora de enfocar, desarrollar y revisar sus
respectivas contribuciones. Se agradece también a Damiana C. Pucciarelli,
quien llevó adelante la traducción al inglés del material Anexo y al Dr. S.
Ivan Perez quien compiló y revisó la base de datos anexa. Asimismo, agradecen
efusivamente la labor editorial pulcra y eficiente de María Cristina Muñe,
compañera de vida de nuestro homenajeado y de la Dra. María Fernanda
Torres. Ambas volcaron su cariño, profesionalismo y dedicación en el maquetado
de este libro. Y por supuesto: gracias a Héctor, por ser el Maestro
de tantos.
... El poblamiento Americano ha sido durante décadas un tema de debate cuya discusión continúa hasta hoy en día Powell y Neves, 1999;Goebel et al., 2008;Meltzer, 2009). Particularmente, la variación biológica de las poblaciones americanas fue investigada de manera intensiva durante los últimos ciento cincuenta años (e.g., Lund, 1842;Ameghino, 1909;Turner, 1983;Neves y Pucciarelli, 1991;Bonatto y Salzano, 1997;Moraga et al., 2005;de Saint Pierre et al., 2012;Battaglia et al., 2013;de Azevedo et al., 2015;. Los análisis morfológicos comparativos entre los esqueletos americanos más tempranos y más recientes han sugerido la existencia de un escenario complejo subyacente a la evolución biológica de estas poblaciones. ...
... De esta discusión se desprende que debido a la importancia que podría tener la plasticidad y otros factores locales en la divergencia morfológica, usar sólo análisis morfométricos craneanos resulta insuficiente para apoyar las hipótesis de que las diferencias morfológicas entre muestras americanas tempranas y tardías están relacionadas con procesos migratorios o el modelo de los dos componentes biológicos. En este sentido, si bien actualmente la mayoría de los estudios moleculares sugieren que todas las poblaciones sudamericanas habrían descendido de una misma población ancestral y por tanto, las diferencias morfológicas son el resultado de procesos evolutivos locales (Merriwether et al., 1995;Schurr, 2004;Perego et al., 2009;Reich et al., 2012;de Azevedo et al., 2015;Raghavan et al., 2015;Scott et al., 2016), algunos resultados aislados le dan un soporte relativo al modelo de los dos componentes biológicos (Skoglund et al., 2015). Por lo tanto, aunque la evidencia craneométrica es muy importante para comprender el poblamiento humano y la diversificación en América, estudios y modelos futuros sobre el poblamiento americano basados en este tipo de evidencias deben incorporar mayor cantidad de datos moleculares, morfológicos y arqueológicos en conjunto. ...
... To increase sample size, both males and females were projected. Potential sexrelated differences were mitigated following the approach by de Azevedo et al. (2017) where male and female aligned coordinates are calculated based on the difference between the male and female average. ...
In Quebec, written accounts of free or enslaved Indigenous and African individuals during colonial times are few and limited. Three-dimensional geometric morphometric methods applied on 214 temporal bones individuals are used to explore intra-cemetery population variation throughout three centuries (1683-1878), to identify plausible non-European or admixed individuals. First, Principal Component Analysis (PCA) was generated from populations originated from Africa, North-America (Indigenous) and Europe where colonial cemeteries are projected to assess their degree of overlap with the reference groups. Second, Discriminant Function Analysis (DFA) based on typicality probabilities also allowed to assign unknown individuals to the three reference groups. Our results highlighted discrepancy between PCA and DFA. With the PCA, Quebec colonial groups overlap with the Europeans except for three individuals. For the DFA, 64 % (n = 136) were classified as typical to one group and 36 % as atypical (n = 77). Most were European, (82 %; n = 112), followed by those as Indigenous (7 %; n = 10), intermediate between Africans and Indigenous (6 %; n = 8) and Africans (5 %; n = 7). Compared with previous research, one individual from the first Protestant cemeteries of St-Matthew in Quebec could be assessed as plausible African or admixed origin. Two others need further analysis: one from St-Matthew and one from the first Catholic cemetery of Notre-Dame in Montreal. Finally, in response to dominant narratives that focused mainly on Euro-colonists, this research provided for the first time a new snapshot of several colonial population diversity in Quebec, underlining the presence of marginalized groups-especially those of African origin, who are absent from the archaeological reports under study.
... relethjh/programs/). Minimum F ST values s (h 2 = 0.55) accounting for minimal environmental influence was estimated for the two earliest Montreal cemeteries (Notre-Dame and old Saint-Antoine) and then each of the other cemeteries were added one at a time, to measure how much between-group variance contributed to each cemetery independently (following deAzevedo et al., 2017 andStrauss et al., 2015). Minimum F ST estimates represent a measurement of the amount of variance from the differences observed between groups(Strauss et al., 2015).Because the effective (or census) population sizes remain unknown, all populations were assumed to have an equal weight in the analysis. ...
Objectives
In Quebec, genetic and genealogical research are used to document migratory events and family structures since colonial times, because bioarchaeological analysis is limited by poor skeletal preservation. This article aims to fill this gap by exploring past population structure in the St‐Lawrence Valley from the French (1683–1760) and British (1760–1867) regimes using morphological variation of well‐preserved temporal bones.
Materials and Methods
3D geometric morphometrics shape data from seven populations (five Catholics of French descent and two Protestants of British descent; n = 214) were collected from temporal bones. Using Procrustes distances and both MANOVA and Discriminant Function Analysis, morphological differences were measured to calculate affinities patterns among populations. Shape variations were explored with between‐group analysis, Mahalanobis distances and quantified by means of Fst estimates using Relethford–Blangero analysis.
Results
Despite strong affinities between all Catholic cemeteries, all show divergent morphological regional diversity ‐especially Montreal and the fortified villages dedicated to its defense. Montreal exhibits low increase in morphological variance over three centuries. As our results show no morphological differences between the Catholic and the Protestant cemeteries in Montreal, this fact may highlight the potential presence of Irish or admixed individuals in Montreal cemeteries after the British takeover.
Discussion
Patterns of morphological diversity highlighted that French colonists did not equally contribute to the descendant populations as reflected by significant interregional variation. Although historical records show that French and English‐speaking populations did not tend to admix, morphological affinities between Protestants and Catholics in the beginning of the industrial era in Montreal could reflect the genetic contribution of Catholic Irish migrants.
Research Highlights
All Catholic cemeteries display distinct morphologies, highlighting differential contributions from French colonists and founder effects, which have increased regional differences.
Montreal Catholic (French descent) and Protestant (English colonists) cemeteries show significant morphological affinities at the beginning of the industrial era.
The Irish migration following the British conquest may explain morphological similarities observed between Catholic and Protestant cemeteries.
... 3 In Brazil, there is a lack of anthropometric data for the different bones that make up the human skeleton; these data are of paramount importance given the high degree of miscegenation of the Brazilian people, which enabled many factors of anatomical variability. 4,5,6 In order to assist the criminal area, due to the exorbitant increase in this violence across the country and the lack of resources offered in inland cities, anthropometry has been gaining prominence for being a safe, low cost, and fast method. However, it is necessary to have independent standards for each Brazilian region for identifying bones, which must be precisely calculated and then compared to other international data. ...
Considering that Brazil does not have an anthropometric database to characterize its population, it is essential to obtain data to standardize craniometric measurements to assist human identification. The present work aims to obtain the metric variations of the mandible of adult Brazilians of full toothed (FT), total toothless (TT), and partial toothless (PT) adult Brazilian mandibles, which were measured in millimeters using a digital caliper. The data obtained were: Depth of the body of the mandible (88.15mm for FT, 85.08mm for TT, and 88.47mm for PT); Intercondylar width (115.4mm for FT, 113.1mm for TT, and 115.8mm for PT); intercoronoid width (94.95mm for FT, 93.99mm for TT, and 94.67mm for PT); bigonial width (94.95mm for FT, 94.7mm for TT, and 95.66mm for PT); mentonian height average (28.15mm for FT, 23.01mm for TT, and 27.29mm for PT); length of the body of the mandible (97.32mm for FT, 94.35mm for TT, and 97.27mm for PT); width of the ramus of mandible (33.01mm for FT, 27.81mm for TT and 31.13mm for PT); and coronoid-condylar distance (38.41mm for FT, 36.33mm for TT and 39mm for PT). There were significant differences in the values of mentonian height (MH) when comparing toothed (FT) with toothless (TT) upper and lower maxillaries (p=0.0003), as well as when comparing toothless (TT) with partial edentate (PT) (p=0.0448). Thus, it is suggested that these differences may be related to the absence (total or partial) of the dentition, which can lead to bone absorption and biomechanical remodeling.
... Variabilities are described between native American groups, Asians, and Caucasians. The claimed variability influences the surgical planning and treatment (Dao Trong et al., 2020;de Azevedo et al., 2017;Elliott and Collard, 2009;Galland and Friess, 2016;Harvati and Weaver, 2006;Hubbe et al., 2015). ...
Purpose
Morphological variability of the skull is an important consideration for cranioplasty and implant design. Differences in morphology of the skull based on the ethnicity are known. In a previous study we could show the accuracy and benefits of virtual reconstructions based on a statistical shape model (SSM) for neurocranial defects. As the SSM is trained on European data, the question arises how well this model fares when dealing with patients with a different ethnic background. In this study we aim to evaluate the accuracy and applicability of our proposed method when deploying a cranial SSM generated from European data to estimate missing parts of the neurocranium in a Chinese population.
Methods
We used the same data and methods as in our previous study and compared the outcomes when applied to Chinese individuals. A large unilateral defect on the right side and a bilateral defect were created. The outer surface of the cranial table was reconstructed from CT scans, meshed with triangular elements, and registered to a template. Principal component analysis together with Thin Plate Spines (TPS) deformation was applied to quantify modes of variation. The mesh to mesh distances between the original defects´ surfaces and the reconstructed surface were computed.
Results
Comparing the Chinese test group with the European control group, regarding the entire defect the analysis shows no significant difference for unilateral defects (test vs. control group/0.46 mm ± vs. 0.44 mm). Reconstruction of bilateral defects exhibited only in slightly higher prediction errors than those of unilateral defects (0.49 mm ± vs. 0.45 mm).
Conclusion
The proposed method shows a high accuracy that seems to be ethnical independent - with low error margins for virtual skull reconstruction and implant design.
Clinical relevance: Metallic objects may severely impact image quality in several CBCT devices.
Trial registration number
DRKS00009719.
... On the other hand, there has been a range of differing viewpoints on the extent to which early American crania differ from later-period populations and from each other. For example, recent assessments using a variety of twodimensional (2D) and 3D methodological approaches have demonstrated that some early Americans show morphological affinities to each other and with early Holocene skeletons from the same region (de Azevedo et al. 2015;Kuzminsky 2013;Kuzminsky, Coonerty, andFehren-Schmitz 2017, 2018;Seguchi et al. 2010). ...
Recent discussions of human dispersals into the Americas have integrated available genomic data, locations and dates of archaeological sites, chronologies for initial biological viability of the Pacific coast and western Canadian ice-free corridors, and respective hypotheses to explain the initial peopling of the continents. Currently, these lines of evidence are incomplete given the lack of geographically and chronologically continuous data available for any one avenue of research. Here we discuss the potential for geometric morphometric shape analysis of human skeletal remains and stone projectile artifacts to supplement these data and expand our understanding of human dispersals into the Americas. The evolutionarily plastic nature of human skeletons and artifacts offers an alternative means of testing hypotheses of initial dispersal events and human adaptation to changing climate and ecosystems.
... This test was already been applied to the study of early Hominins and Neotropical monkey's diversification (25)(26)(27), as well as on Neanderthal (28) and modern human craniofacial evolution (e.g. (29,30)). In order to further compare modern human populations and Neanderthal specimens, we first run the β − test considering all human population plus the Neanderthal mean: in this case, we could not reject the null hypothesis of neutral evolution for the nasal shape space (see Table 1, p = 0.43). ...
... Much of the research focused on these early inhabitants of South America has been on skull morphology to address biological affinities of continental and extra-continental populations. Some assessments have revealed that early South Americans have a distinct cranial morphology that is more similar to skeletons outside South America (Hubbe, Neves, Licurgo do Amaral, and Guidon, 2007;Strauss et al., 2015), while others have argued that early and late South American Holocene cranial differences may be less pronounced, with some regional similarities (de Azevedo et al., 2011(de Azevedo et al., , 2015; Gonz alez-Jos e, Bortolini, Santos, & Bonatto, 2008;Kuzminsky, 2013;Kuzminsky, Coonerty, and Fehren-Schmitz, 2017;Manríquez et al., 2011;Men endez et al., 2015). ...
Objectives:
Archaeological and genetic research has demonstrated that the Pacific Coast was a key route in the early colonization of South America. Research examining South American skeletons >8000 cal BP has revealed differences in cranial morphology between early and late Holocene populations, which may reflect distinct migration events and/or populations. However, genetic, cultural, and some skeletal data contradict this model. Given these discrepancies, this study examines ∼9000 years of prehistory to test the hypothesis that Early skeletons have a distinct cranial morphology from later skeletons.
Materials and methods:
Using 3D digital models, craniofacial landmarks, and geometric morphometric analyses, we compared Early Holocene crania (n = 4) to later Chilean samples (n = 90) frequently absent in continental assessments of craniofacial variation. PCA, Mahalanobis distances, posterior and typicality probabilities were used to examine variation.
Results:
Two of the earliest skeletons from northern Chile show clear affinities to individuals from later sites in the same region. However, the hypothesis cannot be rejected as one Early individual from northern Chile and one individual from inland Patagonia did not always show clear affinities to coastal populations.
Discussion:
Biological affinities among northern populations and other regions of Chile align with genetic and archaeological data, supporting cultural and biological continuity along the Pacific Coast. In Patagonia, archaeological data are in accordance with skeletal differences between the Early inland steppe individual and coastal populations. This study incorporates 3D methods and skeletal datasets not widely used in assessments of biological affinity, thus contributing to a critical body of research examining the ancient population history of western South America.
... This test was already been applied to the study of early Hominins and Neotropical monkey's diversification (25)(26)(27), as well as on Neanderthal (28) and modern human craniofacial evolution (e.g. (29,30)). ...
Significance
Due to its role in humidifying and warming the air before it reaches the lungs, adaptations in the internal nasal anatomy are suspected to have been essential for modern humans and Neanderthals during the settlement of Eurasian harsh landscapes. Unfortunately, the lack of soft-tissue evidence in the fossil record precludes any study of Neanderthal respiratory performance. Here, we use warping techniques to reconstruct a generic Neanderthal nose, computational fluid dynamics simulations to compare the respiratory performance on both species, and evolutionary analyses to detect signals of selection. We report striking differences on fluid residence times under cold/dry climatic conditions. Different from previously suggested, our results indicate that both species would have achieved an advantageous species-specific respiratory performance in cold climates.
... The intensity and heterogeneity of the processes that shaped such high morphological variation are still a matter of debate. Morphological variation has been interpreted to be resultant from either different migration waves started since ~15,000 years BP (Hubbe et al. 2010;Neves and Pucciarelli 1991;Skoglund et al. 2015), or from local microevolutionary processes that acted since the diversification from one ancestral population (de Azevedo et al. 2015;Raghavan et al. 2015). Whichever the case, the role of ecological factors such as diet and temperature have been proposed among the most plausible factors for such high degree of morphological variation in the postcranium, splanchnocranium, and the general shape of the cranium (Béguelin 2010;Menéndez 2017;Menéndez et al. 2014Menéndez et al. , 2015Paschetta et al. 2010;Perez and Monteiro 2009;Perez et al. 2011). ...
Explicit consideration of spatial structures has come to play an increasingly important role in understanding the evolutionary and ecological processes behind the observed patterns of morphological variation among human populations. Spatial statistics offers a broad range of techniques that allow to investigate those structures. We applied a set of spatial statistics in order to evaluate the relative contribution of the processes involved in the morphological diversification of the basicranium on late Holocene southern South American populations. Important advantages come from the adoption of a local approach for detecting spatial patterns otherwise homogenized by a global one. Furthermore, using a parametric approach we modeled the role of multiple ecological factors on the morphological variation. The results of our analyses suggest a) the presence of a global latitudinal clustering with the southern coastal samples characterized by a more robust basicranium, and the northern Andean samples showing a more gracile structure; b) the existence of localized spatial structures, such as the Andalgalá sample, which suggest c) localized trajectories of evolutionary history over the significant role of different ecological factors.
Objectives:
Craniofacial morphology (CFM) is often used to address questions about the biological affinities of the earliest Americans, or Paleoindians, but resolution is complicated in part by a lack of well-preserved crania. The Wilson-Leonard 2 (WL-2) Paleoindian skull from Texas has never been fully analyzed because it is crushed and cannot be physically reconstructed. This study employs a digital restoration for comprehensive assessment and analysis of WL-2.
Materials and methods:
High-resolution CT data and geometric morphometrics are used to restore the WL-2 skull and analyze its morphology using 65 craniometric measurements acquired on the restoration. These data allow for a full morphological description and multivariate (Mahalanobis Distance and Principal Component) comparisons to other Paleoindians and recent populations.
Results:
WL-2 has a long, narrow braincase, and a short, modestly prognathic face. Compared with other Paleoindians, she is individually similar to several skulls from Brazil, but aligns most closely with pooled samples from the US and Mexico. WL-2 is most similar to recent populations from Europe, Asia, and the Americas, and markedly different to those from Africa and Australia.
Discussion:
The overall morphology of WL-2 and her association with Asians and Europeans align well with trends identified in other CFM analyses. Her affinity to recent Amerindians contrasts with the findings of many previous CFM studies, but is seemingly consistent with molecular analyses suggesting a close relationship between some Paleoindians and modern American Indians. This study demonstrates the potential for using digital anthropological methods to study other Paleoindian crania whose data value is limited by physical destruction and/or deformation.
This thesis brings together theories of pre-Columbian trans-Pacific contact between Oceania and the Americas and analyses them from a history of ideas perspective. Despite the limited factual evidence, trans-Pacific contact theories between the Americas and Oceania have been discussed in various forms since the sixteenth century and remain a persistent trope. To provide a context for the history of ideas of trans-Pacific contact involving the Americas and Oceania, this thesis addresses the changing conceptions of the Pacific according to scholars from Europe and the Americas, the development of science and later anthropology and archaeology in this region and in the Americas, and the growing understanding of the history of settlement of the Americas and the Pacific. The theories addressed herein include ideas about Polynesia (or other parts of the Pacific) being settled by Amerindians; ideas about the Americas being settled by Polynesians or other Pacific Islanders; crop and animal diffusion in either direction; and cultural diffusion and contact theories. An analysis of the history and current status of the trans-Pacific contact debate shows that new additions to scientific knowledge have been obscured and resulted in an inconclusive and repetitive intellectual trajectory. This thesis proposes a historiographical revision and contextualisation of the theories and evidence in order to contribute to a clearer progression of ideas for one of the most resilient debates in the history of archaeology: the problem of trans-Pacific contacts.
The aim of this paper is to evaluate the craniometric affinities of the only Cuncaicha cranial specimen with other early, middle, and late Holocene South American samples. To do so, the skull was first reconstructed by using computer-aided techniques applied to several μ-CT-scanned fragments. Linear measurements were calculated in the facial skeleton, and compared to specimens from a previously available database. We conducted Principal Component and Discriminant Analysis, calculated Mahalanobis distances to evaluate the similarities of the Cuncaicha specimen with early/middle Holocene samples from South America; we calculated a Δ statistic for testing the neutral hypothesis among Peruvian samples. The results show that Cuncaicha presents shape similarities with Lagoa Santa and Lauricocha, mostly in masticatory and respiratory components. Finally, directional selection explains most of the diversification of Peruvian populations. We discuss our results in the context of migratory pathways, as well as the evolutionary processes behind the human diversification in the Americas.
Resumo A ocupação das Américas tem sido discutida cientificamente desde o século XIX, gerando uma infinidade de modelos explicativos. Por outro lado, há limitações das evidências empíricas das primeiras ocupações, causadas por problemas depreservação e pela baixa visibilidade arqueológica. Nesse aspecto, o uso de dados biológicos de populações humanas atuais e antigas tem fornecido informações cruciais para a interpretação dessas primeiras ocupações. Sob uma perspectivabioarqueológica, ou seja, através do estudo dos remanescentes biológicos humanos em contexto arqueológico, este texto sintetiza o atual entendimento sobre a rota de entrada, a data de entrada inicial, o número de migrações, a subsistência eos rituais mortuários dos primeiros americanos. Os resultados desse panorama sintético indicam que há temáticas de alto consenso (rota de entrada), de consenso intermediário (data de entrada) e de baixo consenso (número de migrações).Por outro lado, temáticas como a saúde e o modo de vida dos habitantes antigos das Américas ainda carecem de estudos mais aprofundados. Este texto ressalta a importância do conhecimento bioarqueológico para a formulação de modelosde ocupação, buscando incorporar de forma equilibrada evidências da América do Sul e do Norte.
Geometric Morphometrics (GM) is a method originally applied in Evolutionary Biology studies, using the analysis of change in size and shape in order to better understand ontogenetic sequences, phylogenetic relations, among other issues. The application of GM in archaeological materials has seen a sharp increase in the last decade, mostly associated with theoretical approaches from Evolutionary Archaeology. This is not an isolated case, since most methods used by Evolutionary Archaeologists have been borrowed from Biology, provoking discussion with regard to the future development of Evolutionary Archaeology and its methods (Lycett, 2015). This article aims to discuss some concepts that have been directly borrowed from the application of GM in Biological Sciences and that have not been subject to much thought when used in Archaeology. Such concepts include homology and landmark types, the concept of modularity, as well as the idea of allometry. As much as archaeologists using GM can learn from past discussions held by biologists regarding the above mentioned concepts, it is high time for archaeologists to further discuss ideas concerning the use of these concepts in archaeological studies.
The date of arrival of humans in the Americas is a long-standing puzzle in archaeology. A vein quartz biface from southern New England (South Hadley, Massachusetts) represents the oldest evidence for human occupation in New England, one of the last places in the United States to be colonized by Homo sapiens. The biface, which was resharpened and reused by a member of a subsequent lithic culture, is dated here to approximately 18,000 years ago, which means that pre-Clovis hunters arrived in Massachusetts just as the most recent glacial maximum was melting back to the north.
An adaptive landscape concept outlined by G.G. Simpson constitutes the major conceptual bridge between the fields of micro- and macroevolutionary study. Despite some important theoretical extensions since 1944, this conceptual bridge has been ignored in many empirical studies. In this article, we review the status of theoretical work and emphasize the importance of models for peak movement. Although much theoretical work has been devoted to evolution on stationary, unchanging landscapes, an important new development is a focus on the evolution of the landscape itself. We also sketch an agenda of empirical issues that is inspired by theoretical developments.
The diversity of the five single nucleotide polymorphisms located in genes of the TP53 pathway (TP53, rs1042522; MDM2, rs2279744; MDM4, rs1563828; USP7, rs1529916; and LIF, rs929271) were studied in a total of 282 individuals belonging to Quechua, Aymara, Chivay, Cabanaconde, Yanke, Taquile, Amantani, Anapia, Uros, Guarani Ñandeva, and Guarani Kaiowá populations, characterized as Native American or as having a high level (> 90%) of Native American ancestry. In addition, published data pertaining to 100 persons from five other Native American populations (Surui, Karitiana, Maya, Pima, and Piapoco) were analyzed. The populations were classified as living in high altitude (≥ 2,500 m) or in lowlands (< 2,500 m). Our analyses revealed that alleles USP7-G, LIF-T, and MDM2-T showed significant evidence that they were selected for in relation to harsh environmental variables related to high altitudes. Our results show for the first time that alleles of classical TP53 network genes have been evolutionary co-opted for the successful human colonization of the Andes.
RESUMEN Las poblaciones humanas varían significativamente en su morfología craneana. Aún se debate hasta dónde ésta variabilidad se ha acumulado a través de procesos neutrales (e.g. deriva genética) o bien por efecto de la selección natural. Entender los procesos evolutivos que dieron origen a esta variación es una de las metas de la biología humana en particular y de la biología evolutiva en general. Para analizar la relación entre los patrones de cambio y variación morfológica observados y los esperados bajo un escenario de evolución neutral, aplicamos un modelo genético cuantitativo sobre una muestra muy amplia de poblaciones que abarcan el continente Americano, Asia y Oceanía. La morfología craneofacial se estudió a partir de medidas lineales correspondientes al método craneofuncional, en donde treinta variables métricas describen los distintos componentes funcionales observables en el cráneo. Los resultados indican que los procesos aleatorios, tales como la deriva genética, no son suficientes para explicar la variación morfológica del cráneo en las poblaciones humanas modernas.
ABSTRACT Human populations vary significantly in cranial morphology. It is still a matter of debate whether this variability has been accumulated through neutral processes (e.g. genetic drift) or natural selection. Understanding the evolutionary processes that gave rise to this variation is one of the goals of modern human biology. To examine the relationship between the patterns of morphological change and the observed versus the expected variation under a neutral evolution scenario, we applied a quantitative genetic model on a large sample of populations covering the Americas, Asia and Oceania. Craniofacial morphology was studied from linear measurements corresponding to the Functional Cranial method, where thirty metric variables describe the different functional components of the skull. Results indicated that random processes, such as drift alone, are not enough to explain the morphological variation of the modern human skull.
The Botocudo Indians were hunter-gatherer groups that occupied the East-Central regions of Brazil decimated during the colonial period in the country. During the 19th century, craniometric studies suggested that the Botocudo resembled more the Paleoamerican population of Lagoa Santa than typical Native Americans groups. These results suggest that the Botocudo Indians might represent a population that retained the biological characteristics of early groups of the continent, remaining largely isolated from groups that gave origin to the modern Native South American variation. Moreover, recently, some of the Botocudo remains have been shown to have mitochondrial and autosomal DNA lineages currently found in Polynesian populations. Here, we explore the morphological affinities of Botocudo skulls within a worldwide context. Distinct multivariate analyses based on 32 craniometric variables show that 1) the two individuals with Polynesian DNA sequences have morphological characteristics that fall within the Polynesian and Botocudo variation, making their assignation as Native American specimens problematic, and 2) there are high morphological affinities between Botocudo, Early Americans, and the Polynesian series of Easter Island, which support the early observations that the Botocudo can be seen as retaining the Paleoamerican morphology, particularly when the neurocranium is considered. Although these results do not elucidate the origin of the Polynesian DNA lineages among the Botocudo, they support the hypothesis that the Botocudo represent a case of late survival of ancient Paleoamerican populations, retaining the morphological characteristics of ancestral Late Pleistocene populations from Asia. Am J Phys Anthropol, 2015. © 2015 Wiley Periodicals, Inc.
© 2015 Wiley Periodicals, Inc.
Significance
Modularity, the tendency for the parts of many biological systems to be organized into semiindependent groups, is crucial to the understanding of diversification and the interaction between a population and its environment. In particular, a population’s response to selection is dependent on its modularity pattern, which, in turn, is molded by selection. How these modular patterns evolve is therefore a central question in biology. We show, using novel individual-level simulations, that directional selection is very efficient at restructuring variation and creating modular patterns in continuous traits and that stabilizing selection can maintain established patterns.
Study of human adaptation to extreme environments is important for understanding our cultural and genetic capacity for survival.
The Pucuncho Basin in the southern Peruvian Andes contains the highest-altitude Pleistocene archaeological sites yet identified
in the world, about 900 meters above confidently dated contemporary sites. The Pucuncho workshop site [4355 meters above sea
level (masl)] includes two fishtail projectile points, which date to about 12.8 to 11.5 thousand years ago (ka). Cuncaicha
rock shelter (4480 masl) has a robust, well-preserved, and well-dated occupation sequence spanning the past 12.4 thousand
years (ky), with 21 dates older than 11.5 ka. Our results demonstrate that despite cold temperatures and low-oxygen conditions,
hunter-gatherers colonized extreme high-altitude Andean environments in the Terminal Pleistocene, within about 2 ky of the
initial entry of humans to South America.
Arctic genetics comes in from the cold
Despite a well-characterized archaeological record, the genetics of the people who inhabit the Arctic have been unexplored. Raghavan et al. sequenced ancient and modern genomes of individuals from the North American Arctic (see the Perspective by Park). Analyses of these genomes indicate that the Arctic was colonized 6000 years ago by a migration separate from the one that gave rise to other Native American populations. Furthermore, the original paleo-inhabitants of the Arctic appear to have been completely replaced approximately 700 years ago.
Science , this issue 10.1126/science.1255832 ; see also p. 1004
El fenotipo craneofacial presente en las poblaciones humanas del noreste asiático es considerado
como una especialización de la morfología craneofacial generalizada del Pleistoceno tardío, y aparece
en el registro arqueológico por primera vez en el este Asiático a mediados del Holoceno. Una
vez evolucionados en Asia, estos rasgos (e.g. marcado aplastamiento facial, bóvedas redondeadas
y maxilares altos, narices angostas) comienzan a dispersarse hacia América y actualmente se observan
con frecuencia variable en las poblaciones del Nuevo Mundo. El origen de dicho fenotipo
generalmente se explica a través de una hipótesis adaptativa, sugiriendo adaptaciones al frío extremo
del Noreste Asiático durante la última glaciación. Sin embargo, dicha hipótesis no se ha evaluado
formalmente utilizando la teoría Genético-Cuantitativa, que permite medir la importancia de
agentes evolutivos estocásticos y no-estocásticos en la partición de la varianza fenotípica. Aquí se
utilizan estimadores de forma morfogeométricos sobre cráneos asiáticos y americanos y se aplica
el modelo de Lande para detectar la acción de la Deriva Genética o la Selección Natural en el origen
de la variación craneofacial.
Because of differences in craniofacial morphology and dentition between the earliest American skeletons and modern Native
Americans, separate origins have been postulated for them, despite genetic evidence to the contrary. We describe a near-complete
human skeleton with an intact cranium and preserved DNA found with extinct fauna in a submerged cave on Mexico’s Yucatan Peninsula.
This skeleton dates to between 13,000 and 12,000 calendar years ago and has Paleoamerican craniofacial characteristics and
a Beringian-derived mitochondrial DNA (mtDNA) haplogroup (D1). Thus, the differences between Paleoamericans and Native Americans
probably resulted from in situ evolution rather than separate ancestry.
Significance
Current consensus indicates that modern humans originated from an ancestral African population between ∼100–200 ka. The ensuing dispersal pattern is controversial, yet has important implications for the demographic history and genetic/phenotypic structure of extant human populations. We test for the first time to our knowledge the spatiotemporal dimensions of competing out-of-Africa dispersal models, analyzing in parallel genomic and craniometric data. Our results support an initial dispersal into Asia by a southern route beginning as early as ∼130 ka and a later dispersal into northern Eurasia by ∼50 ka. Our findings indicate that African Pleistocene population structure may account for observed plesiomorphic genetic/phenotypic patterns in extant Australians and Melanesians. They point to an earlier out-of-Africa dispersal than previously hypothesized.
Clovis, with its distinctive biface, blade and osseous technologies, is the oldest widespread archaeological complex defined in North America, dating from 11,100 to 10,700 (14)C years before present (bp) (13,000 to 12,600 calendar years bp). Nearly 50 years of archaeological research point to the Clovis complex as having developed south of the North American ice sheets from an ancestral technology. However, both the origins and the genetic legacy of the people who manufactured Clovis tools remain under debate. It is generally believed that these people ultimately derived from Asia and were directly related to contemporary Native Americans. An alternative, Solutrean, hypothesis posits that the Clovis predecessors emigrated from southwestern Europe during the Last Glacial Maximum. Here we report the genome sequence of a male infant (Anzick-1) recovered from the Anzick burial site in western Montana. The human bones date to 10,705 ± 35 (14)C years bp (approximately 12,707-12,556 calendar years bp) and were directly associated with Clovis tools. We sequenced the genome to an average depth of 14.4× and show that the gene flow from the Siberian Upper Palaeolithic Mal'ta population into Native American ancestors is also shared by the Anzick-1 individual and thus happened before 12,600 years bp. We also show that the Anzick-1 individual is more closely related to all indigenous American populations than to any other group. Our data are compatible with the hypothesis that Anzick-1 belonged to a population directly ancestral to many contemporary Native Americans. Finally, we find evidence of a deep divergence in Native American populations that predates the Anzick-1 individual.
In this study we evaluated migration models to the Americas by using the information contained in native mitochondrial genomes (mito-genomes) from North America. Molecular and phylogeographic analyses of B2a mitogenomes, which are absent in Eskimo–Aleut and northern Na-Dene speakers, revealed that this haplogroup arose in North America ∼11–13 ka from one of the founder Paleo-Indian B2 mitogenomes. In contrast, haplogroup A2a, which is typical of Eskimo–Aleuts and Na-Dene, but also present in the easternmost Siberian groups, originated only 4–7 ka in Alaska, led to the first Paleo-Eskimo settlement of northern Canada and Greenland, and contrib-uted to the formation of the Na-Dene gene pool. However, mitoge-nomes also show that Amerindians from northern North America, without any distinction between Na-Dene and non–Na-Dene, were heavily affected by an additional and distinctive Beringian genetic input. In conclusion, most mtDNA variation (along the double-conti-nent) stems from the first wave from Beringia, which followed the Pacific coastal route. This was accompanied or followed by a second inland migratory event, marked by haplogroups X2a and C4c, which affected all Amerindian groups of Northern North America. Much later, the ancestral A2a carriers spread from Alaska, undertaking both a westward migration to Asia and an eastward expansion into the circumpolar regions of Canada. Thus, the first American founders left the greatest genetic mark but the original maternal makeup of North American Natives was subsequently reshaped by additional streams of gene flow and local population dynamics, making a three-wave view too simplistic. Native Americans | human mtDNA P leistocene glaciations—particularly the Last Glacial Maxi-mum (LGM)—played an important role in shaping current patterns of animal and plant genetic diversity in many regions of the world. As for humans, the lowered sea level uncovered ∼20% more terrain, which in some places acted as natural land-bridges that facilitated expansions to new and unexplored regions, in-cluding the American double-continent (1, 2). The general consensus is that modern Native Americans trace their ancestry to a limited number of original founders whose gene pool ultimately derived from Asian groups that peopled northeast Siberia, in-cluding parts of Beringia, before the LGM (3–7). The ancestral Beringian populations probably retreated into refugia during the Ice Age, where their genetic variation was reshaped not only be-cause of drift, but also because of admixture with population groups newly arrived from regions located west of Beringia. Thus, pre-LGM haplotypes of Asian ancestry were differently preserved, modified, and lost in Beringian enclaves (8–13). One very contentious issue is whether the settlement occurred by means of a single (14–16) or multiple (17–21) streams of mi-gration. In developing hypotheses to address these questions, most analyses of Native American genetic diversity have examined single loci, particularly the maternally inherited mitochondrial DNA (mtDNA), and some interpretations of modern and ancient data point to a major migratory wave from Beringia dated between 15 and 18 ka (14, 22–25). However, a recent genome-wide scan (364,470 SNPs) of Native American and Siberian groups (26) identified three different source populations for Native Americans that revived a more complex and long-debated scenario, also known as the tripartite migration model, which was originally proposed by combining anthropometric, genetic, and linguistic data (19, 27–29). This scenario postulates that the Americas were settled through three separate population movements whose identity was expressed in linguistic terms as Amerinds, Na-Dene, and Eskimo–Aleut speakers (SI Text). Although recent (26) and some very early nuclear (28) and mtDNA (18, 30, 31) data would favor a minimum of three distinct streams of gene flow from Beringian/Siberian sources, neither this model, nor the alternative scenarios have been fully evaluated by using the information contained in the entire mitochondrial ge-nome (mitogenome). To evaluate this issue, we focused on mito-genomes belonging to two haplogroups, known as A2a and B2a, which are characterized by peculiar geographic distributions. Among the numerous subclades radiating from the root of the pan-American haplogroup A2 (32–34), A2a (together with A2b) mtDNAs have been mostly identified only in Siberia, in Alaska, and the surrounding regions, and in Natives from the American Southwest (21, 31, 35–41). B2a radiates from the root of B2, another common pan-American haplogroup. However, this particular B2 branch has also been observed exclusively in North America, just to the south and more widespread than A2a (42). In this study we report 41 additional mitogenomes belonging to A2a and B2a as well as detailed phylogeographic analyses of the two haplogroups in the general context of North American mtDNA variation.
The origins of the First Americans remain contentious. Although Native Americans seem to be genetically most closely related to east Asians, there is no consensus with regard to which specific Old World populations they are closest to. Here we sequence the draft genome of an approximately 24,000-year-old individual (MA-1), from Mal'ta in south-central Siberia, to an average depth of 1×. To our knowledge this is the oldest anatomically modern human genome reported to date. The MA-1 mitochondrial genome belongs to haplogroup U, which has also been found at high frequency among Upper Palaeolithic and Mesolithic European hunter-gatherers, and the Y chromosome of MA-1 is basal to modern-day western Eurasians and near the root of most Native American lineages. Similarly, we find autosomal evidence that MA-1 is basal to modern-day western Eurasians and genetically closely related to modern-day Native Americans, with no close affinity to east Asians. This suggests that populations related to contemporary western Eurasians had a more north-easterly distribution 24,000 years ago than commonly thought. Furthermore, we estimate that 14 to 38% of Native American ancestry may originate through gene flow from this ancient population. This is likely to have occurred after the divergence of Native American ancestors from east Asian ancestors, but before the diversification of Native American populations in the New World. Gene flow from the MA-1 lineage into Native American ancestors could explain why several crania from the First Americans have been reported as bearing morphological characteristics that do not resemble those of east Asians. Sequencing of another south-central Siberian, Afontova Gora-2 dating to approximately 17,000 years ago, revealed similar autosomal genetic signatures as MA-1, suggesting that the region was continuously occupied by humans throughout the Last Glacial Maximum. Our findings reveal that western Eurasian genetic signatures in modern-day Native Americans derive not only from post-Columbian admixture, as commonly thought, but also from a mixed ancestry of the First Americans.
Although cranial gracility is generally considered to be a characteristic feature of modern skulls, a quantification of the degree of development of cranial superstructures discloses varying levels of robusticity in certain recent and sub-recent populations. In order to account for these structures, biomechanical interpretations in terms of masticatory stress and the effects of structural constraints have been put forward. This paper examines the multivariate relationships between robusticity and cranial dimensions in modern humans through canonical correlation and principal components analyses. These analyses reveal a very significant association between robusticity and cranial size, by which the larger the size of the skull, the greater the development of the cranial superstructures. In this context, size is biased towards maximum cranial length, various measures of upper facial breadth, basion–nasion length and palato–dental size. A statistically less important relationship between robusticity and cranial shape reveals that there are two main circumstances in which a modern skull will develop superstructures, in either very large crania, independent of the breadth of the vault, or in very narrow ones with large teeth. The cranial superstructures are not only strongly influenced by certain cranial dimensions, but are inter-correlated in their expression. These morphological features should not be treated as independent phylogenetic traits.
The study of cranial variation has a long, and somewhat difficult, history within anthropology. Much of this difficulty is rooted in the historical use of craniometric data to justify essentialist typological racial classification schemes. In the post-war era of the "New Physical Anthropology" (sensu Washburn, 1951), anthropologists began to analyse human variation in an explicitly populationist and evolutionary philosophical and analytical framework. However, even within recent decades, substantially different approaches have been employed; some advocate a focus on the analysis of individual traits or clines, while others are explicitly adaptationist, with a focus on natural selection as the preeminent force of phenotypic diversification. In recent years, a series of studies have analysed craniometric data in an explicitly quantitative genetic framework, which emphasises the importance of neutral forces such as migration, gene flow and genetic drift in creating global patterns of phenotypic diversity. This approach has revealed that global patterns of cranial variation can largely be explained on the basis of neutral theory. Therefore, human cranial data can be productively employed as a proxy for neutral genetic data in archaeological contexts. Moreover, there is a growing recognition that regions of the cranium differ in the extent to which they fit a neutral model of microevolutionary expectation, allowing for a more detailed assessment of patterns of adaptation and phenotypic plasticity within the human skull. Taking an historical perspective, the current state of knowledge regarding patterns of cranial adaptation in response to climatic and dietary effects is reviewed. Further insights will be gained by better incorporating the study of cranial and postcranial variation, as well as understanding the impact of neutral versus non-neutral evolution in creating among-species diversity patterns in primates more generally. However, this will most effectively be achieved when comparative anatomy studies are situated within an explicitly quantitative genetic evolutionary framework.
In this study we evaluated migration models to the Americas by using the information contained in native mitochondrial genomes (mitogenomes) from North America. Molecular and phylogeographic analyses of B2a mitogenomes, which are absent in Eskimo-Aleut and northern Na-Dene speakers, revealed that this haplogroup arose in North America ∼11-13 ka from one of the founder Paleo-Indian B2 mitogenomes. In contrast, haplogroup A2a, which is typical of Eskimo-Aleuts and Na-Dene, but also present in the easternmost Siberian groups, originated only 4-7 ka in Alaska, led to the first Paleo-Eskimo settlement of northern Canada and Greenland, and contributed to the formation of the Na-Dene gene pool. However, mitogenomes also show that Amerindians from northern North America, without any distinction between Na-Dene and non-Na-Dene, were heavily affected by an additional and distinctive Beringian genetic input. In conclusion, most mtDNA variation (along the double-continent) stems from the first wave from Beringia, which followed the Pacific coastal route. This was accompanied or followed by a second inland migratory event, marked by haplogroups X2a and C4c, which affected all Amerindian groups of Northern North America. Much later, the ancestral A2a carriers spread from Alaska, undertaking both a westward migration to Asia and an eastward expansion into the circumpolar regions of Canada. Thus, the first American founders left the greatest genetic mark but the original maternal makeup of North American Natives was subsequently reshaped by additional streams of gene flow and local population dynamics, making a three-wave view too simplistic.
Superimposition methods for comparing configurations of landmarks in two or more specimens are reviewed. These methods show
differences in shape among specimens as residuals after rotation, translation, and scaling them so that they align as well
as possible. A new method is presented that generalizes Siegel and Benson's (1982) resistant-fit theta-rho analysis so that
more than two objects can be compared at the same time. Both least-squares and resistant-fit approaches are generalized to
allow for affine transformations (uniform shape change). The methods are compared, using artificial data and data on 18 landmarks
on the wings of 127 species of North American mosquitoes. Graphical techniques are also presented to help summarize the patterns
of differences in shape among the objects being compared.
Although it is widely recognised that America was the last continent to be populated by our species, researchers' views on various aspects of this process (e.g. the period in which it occurred, the area from which the colonizing populations came, the number of dispersal waves and the routes taken by these migrations) differ significantly. In this paper, we review both classical data and more recent findings from various research fields - including geology, paleoecology, archaeology, skeletal biology, and genetics - that may shed light on the dynamics of the colonization of the American continent, according to a critical reappraisal of the various hypotheses and models that have been advanced over time to explain this process.
Most studies in evolutionary developmental biology focus on large-scale evolutionary processes using experimental or molecular approaches, whereas evolutionary quantitative genetics provides mathematical models of the influence of heritable phenotypic variation on the short-term response to natural selection. Studies of morphological integration typically are situated in-between these two styles of explanation. They are based on the consilience of observed phenotypic covariances with qualitative developmental, functional, or evolutionary models. Here we review different forms of integration along with multiple other sources of phenotypic covariances, such as geometric and spatial dependencies among measurements. We discuss one multivariate method [partial least squares analysis (PLS)] to model phenotypic covariances and demonstrate how it can be applied to study developmental integration using two empirical examples. In the first example we use PLS to study integration between the cranial base and the face in human postnatal development. Because the data are longitudinal, we can model both cross-sectional integration and integration of growth itself, i.e., how cross-sectional variance and covariance is actually generated in the course of ontogeny. We find one factor of developmental integration (connecting facial size and the length of the anterior cranial base) that is highly canalized during postnatal development, leading to decreasing cross-sectional variance and covariance. A second factor (overall cranial length to height ratio) is less canalized and leads to increasing (co)variance. In a second example, we examine the evolutionary significance of these patterns by comparing cranial integration in humans to that in chimpanzees.
Organisms represent a complex arrangement of anatomical structures and individuated parts that must maintain functional associations through development. This integration of variation between functionally related body parts and the modular organization of development are fundamental determinants of their evolvability. This is because integration results in the expression of coordinated variation that can create preferred directions for evolutionary change, while modularity enables variation in a group of traits or regions to accumulate without deleterious effects on other aspects of the organism. Using our own work on both model systems (e.g., lab mice, avians) and natural populations of rodents and primates, we explore in this paper the relationship between patterns of phenotypic covariation and the developmental determinants of integration that those patterns are assumed to reflect. We show that integration cannot be reliably studied through phenotypic covariance patterns alone and argue that the relationship between phenotypic covariation and integration is obscured in two ways. One is the superimposition of multiple determinants of covariance in complex systems and the other is the dependence of covariation structure on variances in covariance-generating processes. As a consequence, we argue that the direct study of the developmental determinants of integration in model systems is necessary to fully interpret patterns of covariation in natural populations, to link covariation patterns to the processes that generate them, and to understand their significance for evolutionary explanation.
The genetic correlation is a central parameter of quantitative genetics, providing a measure of the rate at which traits respond to indirect selection (i.e., selection that does not act upon the traits under study, but some other trait with which they have genes in common). In this paper, I review the pattern of variation among four combinations of traits: life history × life history (L × L), morphological × morphological (M × M), life history × morphological (L × M), and behavioral × behavioral (B × B). A few other combinations were investigated, but insufficient data were obtained for separate analysis. A total of 1798 correlations, distributed over 51 different animal and plant species, were analyzed. The analysis was conducted at two levels: first by dividing the data set solely by trait combination, and second by blocking the data by trait combination and species. Because selection will tend to fix alleles that show positive correlations with fitness traits faster than those that are negative and because the latter are expected to arise more frequently by mutation, correlations between life-history traits are predicted to be more often negative than those between morphological traits. This prediction was supported, with the ranking in decreasing proportion of negative correlations being: L × L > L × M > B × B > M × M. The mean magnitude of the genetic correlation shows little variation among morphological and life-history combinations, and the distribution of values is remarkably flat. However, the estimated standard errors and the coefficient of variation (SE/rG ) are large, making it difficult to separate biological factors influencing the pattern of dispersion from experimental error. Analysis of the phenotypic and genetic correlations suggest that for the combinations M × M and L × M, but not L × L or B × B, the phenotypic correlation is an adequate estimate of the genetic correlation.
More than 12,000 years ago, in one of the greatest triumphs of prehistory, humans colonized North America, a continent that was then truly a new world. Just when and how they did so has been one of the most perplexing and controversial questions in archaeology. This dazzling, cutting-edge synthesis, written for a wide audience by an archaeologist who has long been at the center of these debates, tells the scientific story of the first Americans: where they came from, when they arrived, and how they met the challenges of moving across the vast, unknown landscapes of Ice Age North America. David J. Meltzer pulls together the latest ideas from archaeology, geology, linguistics, skeletal biology, genetics, and other fields to trace the breakthroughs that have revolutionized our understanding in recent years. Among many other topics, he explores disputes over the hemisphere's oldest and most controversial sites and considers how the first Americans coped with changing global climates. He also confronts some radical claims: that the Americas were colonized from Europe or that a crashing comet obliterated the Pleistocene megafauna. Full of entertaining descriptions of on-site encounters, personalities, and controversies, this is a compelling behind-the-scenes account of how science is illuminating our past.
ABSTRACT
OBJECTIVE: A noticeably well-preserved _12.500 years-old skeleton from the Hoyo Negro cave, Yucatan, Mexico, was recently reported, along with its archaeological, genetic and skeletal characteristics. Based exclusively on an anatomical description of the skull (HN5/ 48), Chatters and colleagues stated that this specimen can be assigned to a set of ancient remains that differ from modern Native Americans, the so called “Paleoamericans”. Here, we aim to further explore the morphological affinities of this specimen with a set of comparative cranial samples covering ancient and modern periods from Asia and the Americas.
METHODS: Images published in the original article were analyzed using geometric morphometrics methods. Shape variables were used to perform Principal Component and Discriminant analysis against the reference samples.
RESULTS: Even thought the Principal Component Analysis suggests that the Hoyo Negro skull falls in a subregion of the morphospace occupied by both “Paleoamericans” and some modern Native Americans, the Discriminant analyses suggest greater affinity with a modern Native American sample.
DISCUSSION: These results reinforce the idea that the original population that first occupied the New World carried high levels of within-group variation, which we have suggested previously on a synthetic model for the settlement of the Americas. Our results also highlight the importance of developing formal classificatory test before deriving settlement hypothesis purely based on macroscopic descriptions. Am J Phys Anthropol 158:514– 521, 2015.
A noticeably well-preserved ∼12.500 years-old skeleton from the Hoyo Negro cave, Yucatán, México, was recently reported, along with its archaeological, genetic and skeletal characteristics. Based exclusively on an anatomical description of the skull (HN5/48), Chatters and colleagues stated that this specimen can be assigned to a set of ancient remains that differ from modern Native Americans, the so called "Paleoamericans". Here, we aim to further explore the morphological affinities of this specimen with a set of comparative cranial samples covering ancient and modern periods from Asia and the Americas.
Images published in the original article were analyzed using geometric morphometrics methods. Shape variables were used to perform Principal Component and Discriminant analysis against the reference samples.
Even thought the Principal Component Analysis suggests that the Hoyo Negro skull falls in a subregion of the morphospace occupied by both "Paleoamericans" and some modern Native Americans, the Discriminant analyses suggest greater affinity with a modern Native American sample.
These results reinforce the idea that the original population that first occupied the New World carried high levels of within-group variation, which we have suggested previously on a synthetic model for the settlement of the Americas. Our results also highlight the importance of developing formal classificatory test before deriving settlement hypothesis purely based on macroscopic descriptions. Am J Phys Anthropol, 2015. © 2015 Wiley Periodicals, Inc.
© 2015 Wiley Periodicals, Inc.
Here we evaluate morphological integration patterns and magnitudes in different skull regions to detect if shifts in morphological integration are correlated to the appearance of more processed (softer) diets.
To do so, three transitional populations were analyzed, including samples from groups that inhabited the same geographical region and for which the evidence shows that major changes occurred in their subsistence mode. Ninety three-dimensional landmarks were digitized on 357 skulls and used as the raw data to develop geometric morphometric analyses. The landmark coordinates were divided into several different regions of biomechanical interest, following a three-level hierarchically nested scheme: the whole skull, further subdivided into neurocranium (divided into the vault and basicranium), the facial (divided into the lower and upper facial), and the masticatory apparatus (divided into alveolar, temporal, and temporo-mandibular joint).
Our results indicate that the morphological integration and variability patterns significantly vary across skull regions but are maintained across the transitions. The alveolar border and the lower facial are the regions manifesting greater value of morphological integration and variability, while the upper facial, the temporo-mandibular joint, and the basicranium are highly integrated and poorly variable.
The transition to softer diets increased morphological variation across cranial regions that are more exposed to masticatory strains effects. Am. J. Hum. Biol., 2015. © 2015 Wiley Periodicals, Inc.
© 2015 Wiley Periodicals, Inc.
Genetic variances and correlations lie at the center of quantitative evolutionary theory. They are often difficult to estimate, however, due to the large samples of related individuals that are required. I investigated the relationship of genetic- and phenotypic-correlation magnitudes and patterns in 41 pairs of matrices drawn from the literature in order to determine their degree of similarity and whether phenotypic parameters could be used in place of their genetic counterparts in situations where genetic variances and correlations cannot be precisely estimated. The analysis indicates that squared genetic correlations were on average much higher than squared phenotypic correlations and that genetic and phenotypic correlations had only broadly similar patterns. These results could be due either to biological causes or to imprecision of genetic-correlation estimates due to sampling error. When only those studies based on the largest sample sizes (effective sample size of 40 or more) were included, squared genetic-correlation estimates were only slightly greater than their phenotypic counterparts and the patterns of correlation were strikingly similar. Thus, much of the dissimilarity between phenotypic- and genetic-correlation estimates seems to be due to imprecise estimates of genetic correlations. Phenotypic correlations are likely to be fair estimates of their genetic counterparts in many situations. These further results also indicate that genetic and environmental causes of phenotypic variation tend to act on growth and development in a similar manner.
A current issue on the settlement of the Americas refers to the lack of morphological affinities between early Holocene human remains (Palaeoamericans) and modern Amerindian groups, as well as the degree of contribution of the former to the gene pool of the latter. A different origin for Palaeoamericans and Amerindians is invoked to explain such a phenomenon. Under this hypothesis, the origin of Palaeoamericans must be traced back to a common ancestor for Palaeoamericans and Australians, which departed from somewhere in southern Asia and arrived in the Australian continent and the Americas around 40,000 and 12,000 years before present, respectively. Most modern Amerindians are believed to be part of a second, morphologically differentiated migration. Here we present evidence of a modern Amerindian group from the Baja California Peninsula in Mexico, showing clearer affinities with Palaeoamerican remains than with modern Amerindians. Climatic changes during the Middle Holocene probably generated the conditions for isolation from the continent, restricting the gene flow of the original group with northern populations, which resulted in the temporal continuity of the Palaeoamerican morphological pattern to the present.
Geometric Morphometrics for Biologists is an introductory textbook for a course on geometric morphometrics, written for graduate students and upper division undergraduates, covering both theory of shape analysis and methods of multivariate analysis. It is designed for students with minimal math background; taking them from the process of data collection through basic and more advanced statistical analyses. Many examples are given, beginning with simple although realistic case-studies, through examples of complex analyses requiring several different kinds of methods. The book also includes URLâs for free software and step-by-step instructions for using the software.
Increasingly, data on shape are analysed in combination with molecular genetic or ecological information, so that tools for geometric morphometric analysis are required. Morphometric studies most often use the arrangements of morphological landmarks as the data source and extract shape information from them by Procrustes superimposition. The MorphoJ software combines this approach with a wide range of methods for shape analysis in different biological contexts. The program offers an integrated and user-friendly environment for standard multivariate analyses such as principal components, discriminant analysis and multivariate regression as well as specialized applications including phylogenetics, quantitative genetics and analyses of modularity in shape data. MorphoJ is written in Java and versions for the Windows, Macintosh and Unix/Linux platforms are freely available from http://www.flywings.org.uk/MorphoJ_page.htm.
,*† ,‡ DN REZNICK§ and CW FOX¶ *Department of Entomology and Center for Population Biology, University of California, Davis, CA 95616 USA, ‡Redpath Museum and Department of Biology, McGill University, Montréal, Québec, Canada H3A 2K6, §
During the Late Pleistocene, anatomically modern humans (AMH) dispersed out of Africa. They first spread north with game, across the Sahara to the Levant during the Eemian interglacial (c.125 ka); and there is some recent evidence they may also have spread via Arabia to the Far East at the same time. However, they failed to continue to Europe, then occupied by Neanderthals. The Sahara and Arabia then reverted to aridity, and AMH vanished from the fossil record after 92 ka, being later replaced in the Levant, again by Neanderthals. There is recent fragmentary evidence AMH may also have spread via Arabia to the Far East, but the archaeological record fades similarly, long before the Toba eruption. There is no evidence of surviving non-African DNA lineages, dating from anywhere near the Eemian, to contradict this narrative. Genetic evidence indicates that AMH successfully left Africa much later, as a single group, by the southern route to India. Since all non-African uniparental lineages date to this later exit, this appears to have been the only ultimately successful AMH exit. AMH reached the isolated Sahul continent at least by 48 ka and possibly by 60–50 ka. AMH only finally arrived in Europe from South Asia before 46 ka, probably linked to climatic amelioration during MIS-3.
Advances in large-scale paleogeographic reconstruction define physical and environmental constraints relevant to understanding the timing and character of the first colonization of the Americas during the late Pleistocene. Diachronic mapping shows continental glaciers coalesced in central Canada during the Last Glacial Maximum (LGM) 20,000–14,000 years ago while unglaciated refugia existed along the Northwest Coast. The Bering Land Bridge connected Asia and North America until about 10,000 years ago when the two continents were separated by rising sea level. This visual analysis from large-scale synthesis of recent geological and environmental research establishes timelines for biotically viable colonization corridors connecting eastern Beringia to southern North America and provides insights into probable Paleoindian origins and subsistence strategies.
The classification of the indigenous languages of the Americas by Greenberg distinguishes three stocks, Amerind, Na-Dene, and Aleut-Eskimo. The first of these covers almost all of the New World. The second consists of Na-Dene as defined by Sapir and, outside of recent. Athapaskan extensions in California and the American Southwest, is found in southern Alaska and northwestern Canada. The third, Aleut-Eskimo, is the easternmost branch of the Eurasiatic language family located in northern Asia and Europe. These three linguistic stocks are found to agree well with the three dental groups proposed by Turner and the genetic divisions of the New World population advanced by Zegura. The three groups are hypothesized as representing the settlement of the New World by successive migrations from Asia. The earliest is in all probability the Amerind; the relative priority of Na-Dene to Aleut-Eskimo is less certain. The evidence regarding the absolute chronology of these proposed migrations is discussed.
A basic principle of natural selection on correlated characters is expressed as an adaptive topography for the vector of mean phenotypes in a population. Under some simple conditions on the pattern of phenotypic and genetic covariation within populations, selection only on body size, certain types of multivariate selection, and random genetic drift in a stochastic phylogeny are each expected to produce allometric evolution, i.e., straight lines or linear regressions on logarithmic coordinates. The orientation of these lines is determined by genetic parameters of the populations. Using this theory, phylogenetic or comparative information can be combined with experimental data on population genetic parameters to test hypotheses about past selective forces. Data from selection experiments on brain and body weights in mice support the conclusions that [1] the short-term differentiation of brain and body sizes in very closely related mammalian forms resulted either from directional selection mostly on body size with changes in brain sizes largely a genetically correlated response, or from random genetic drift; [2] during the long-term allometric diversification within most mammalian orders there has been more net directional selection on brain sizes than on body sizes. It is suggested that encephalization in primates decreased the genetic correlation between brain size and body size within populations, which facilitated further encephalization in the human lineage by avoiding antagonistic selection on brain and body sizes. The evolution of brain:body ontogeny is briefly discussed.
The cranial morphology of early South American human remains are compared with Late Pleistocene and Early Holocene worldwide human morphological variation by means of a principal components analysis applied to 13 craniometric variables. Two modern Mongoloid populations and one Australoid population were also included as controls. The morphological affinities obtained showed evidence of a marked biological similarity between early South Americans and early and modern Australians, and a considerable distance between both populations and the Mongoloid groups used as control. These results call for more detailed investigations about human micro-evolution in the Americas, including time of entry and number of migrations involved.
▪ Abstract A number of important insights into the peopling of the New World have been gained through molecular genetic studies of Siberian and Native American populations. These data indicate that the initial migration of ancestral Amerindian originated in south-central Siberia and entered the New World between 20,000–14,000 calendar years before present (cal yr BP). These early immigrants probably followed a coastal route into the New World, where they expanded into all continental regions. A second migration that may have come from the same Siberian region entered the Americas somewhat later, possibly using an interior route, and genetically contributed to indigenous populations from North and Central America. In addition, Beringian populations moved into northern North America after the last glacial maximum (LGM) and gave rise to Aleuts, Eskimos, and Na-Dené Indians.