Genetics of the peloponnesean populations and the theory of extinction of the medieval peloponnesean Greeks

Abstract

Peloponnese has been one of the cradles of the Classical European civilization and an important contributor to the ancient European history. It has also been the subject of a controversy about the ancestry of its population. In a theory hotly debated by scholars for over 170 years, the German historian Jacob Philipp Fallmerayer proposed that the medieval Peloponneseans were totally extinguished by Slavic and Avar invaders and replaced by Slavic settlers during the 6th century CE. Here we use 2.5 million single-nucleotide polymorphisms to investigate the genetic structure of Peloponnesean populations in a sample of 241 individuals originating from all districts of the peninsula and to examine predictions of the theory of replacement of the medieval Peloponneseans by Slavs. We find considerable heterogeneity of Peloponnesean populations exemplified by genetically distinct subpopulations and by gene flow gradients within Peloponnese. By principal component analysis (PCA) and ADMIXTURE analysis the Peloponneseans are clearly distinguishable from the populations of the Slavic homeland and are very similar to Sicilians and Italians. Using a novel method of quantitative analysis of ADMIXTURE output we find that the Slavic ancestry of Peloponnesean subpopulations ranges from 0.2 to 14.4%. Subpopulations considered by Fallmerayer to be Slavic tribes or to have Near Eastern origin, have no significant ancestry of either. This study rejects the theory of extinction of medieval Peloponneseans and illustrates how genetics can clarify important aspects of the history of a human population.European Journal of Human Genetics advance online publication, 8 March 2017; doi:10.1038/ejhg.2017.18.

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ARTICLE
Genetics of the peloponnesean populations and
the theory of extinction of the medieval
peloponnesean Greeks
George Stamatoyannopoulos*,1, Aritra Bose2, Athanasios Teodosiadis3, Fotis Tsetsos2, Anna Plantinga4,
Nikoletta Psatha5, Nikos Zogas6, Evangelia Yannaki6, Pierre Zalloua7, Kenneth K Kidd8, Brian L Browning4,9,
John Stamatoyannopoulos3,10, Peristera Paschou11 and Petros Drineas2
Peloponnese has been one of the cradles of the Classical European civilization and an important contributor to the ancient
European history. It has also been the subject of a controversy about the ancestry of its population. In a theory hotly debated by
scholars for over 170 years, the German historian Jacob Philipp Fallmerayer proposed that the medieval Peloponneseans were
totally extinguished by Slavic and Avar invaders and replaced by Slavic settlers during the 6th century CE. Here we use 2.5
million single-nucleotide polymorphisms to investigate the genetic structure of Peloponnesean populations in a sample of 241
individuals originating from all districts of the peninsula and to examine predictions of the theory of replacement of the medieval
Peloponneseans by Slavs. We find considerable heterogeneity of Peloponnesean populations exemplified by genetically distinct
subpopulations and by gene flow gradients within Peloponnese. By principal component analysis (PCA) and ADMIXTURE analysis
the Peloponneseans are clearly distinguishable from the populations of the Slavic homeland and are very similar to Sicilians and
Italians. Using a novel method of quantitative analysis of ADMIXTURE output we find that the Slavic ancestry of Peloponnesean
subpopulations ranges from 0.2 to 14.4%. Subpopulations considered by Fallmerayer to be Slavic tribes or to have Near Eastern
origin, have no significant ancestry of either. This study rejects the theory of extinction of medieval Peloponneseans and
illustrates how genetics can clarify important aspects of the history of a human population.
European Journal of Human Genetics advance online publication, 8 March 2017; doi:10.1038/ejhg.2017.18
INTRODUCTION
Peloponnese was peopled by a series of migrations that spanned
almost nine millennia. Early migrants arrived from Anatolia ca
9000 BCE1,2 and established in the peninsula several Neolithic
sites.2The Myceneans3who developed an advanced Bronze Era
civilization, either migrated from the north around 2200 BCE4,5 or
were the descendants of the original Neolithic migrants.1The next
migration took place at the beginning of the first millennium BCE
with the invasion of Peloponnese by the Dorian Greeks, referred in
the Greek tradition as the return of the Heraclids.6The subsequent
14 centuries were marked by quantitative changes of the popu-
lation due to wars and epidemics but no qualitative effects from
migrations of new population groups. Changes in population
structure started in the beginning of the medieval period with the
migrations of the Slavs to the Balkans.7,8 The effects of these
migrations have dominated the historiography of Peloponnese
during the last 170 years.
In 1830 CE, the German historian Jacob Philipp Fallmerayer
presented his theory of disappearance of the Greek nation and its
substitution by Slavs.9Fallmerayer proposed that during the 6th
century CE, large armies of Avars and Slavs overran the Balkans and
eliminated the populations of the Hellas, who up to that period had
successfully survived the attacks of barbarians and the religious
suppression by the Byzantines. The Peloponnesean Greeks, except
for few remnants enclosed in coastal castles, were slaughtered or
forced to leave and Peloponnese was inhabited by Slavic tribes. The
Slavs kept their identity for few centuries but eventually they were
Hellenized under the influence of the Orthodox Church and interac-
tions with Hellenized Asia Minor populations who were settled in
Peloponnese by the Byzantines. Since the time Fallmerayer’stheory
was published, a debate on the question of the ancestry of Pelopon-
neseans has raged among historians (reviewed in Curta,10). Of note is
that in spite of their diametrically different views, all historians have
been using the same medieval written sources.
Controversies are rather common in historiography and result
to endless debates among scholars. Controversies concerning
the ancestry of populations can potentially be resolved by
genetic analysis. In this paper, we use genome-wide data to study
the genetic structure of the Peloponnesean populations and
compare them with other populations of the world. We observe
1
Division of Medical Genetics, Departments of Medicine and Genome Sciences, University of Washington, Seattle, WA, USA;
2
Department of Computer Sciences, Purdue
University, West Lafayette, Indiana;
3
Altius Institute for Biomedical Sciences, Seattle, WA, USA;
4
Department of Biostatistics, University of Washington, Seattle, WA, USA;
5
Division
of Hematology, Department of Medicine, University of Washington, Seattle, WA, USA;
6
Department of Hematology, George Papanicolaou Hospital, Thessaloniki, Greece;
7
Graduate Studies and Research Lebanese American University, Beirut, Lebanon;
8
Department of Genetics, Yale University School of Medicine, New Haven, CT, USA;
9
Division of
Medical Genetics, Department of Medicine, University of Washington, Seattle, WA, USA;
10
Departments of Medicine and Genome Sciences, University of Washington, Seattle, WA,
USA;
11
Department of Molecular Biology and Genetics, Democritus University of Thrace, Alexandroupolis, Greece
*Correspondence: Professor G Stamatoyannopoulos, Division of Medical Genetics, Departments of Medicine and Genome Sciences, University of Washington, Box 357720,
Seattle, WA 98195, USA. Tel: +206 543 3526; Fax: +206 221 5112; E-mail: gstam@uw.edu
Received 13 September 2016; revised 14 December 2016; accepted 22 January 2017
European Journal of Human Genetics (2017), 1–9
Official journal of The European Society of Human Genetics
www.nature.com/ejhg

K=2
K=3
K=4
K=5
K=6
K=7
K=8
Figure 1 Substructure of the Peloponnesean populations. (a) Map of Peloponnese showing the populations studied. Each dot corresponds to the origin of a
participant. (b) PCA illustrating the separation of Peloponneseans in three groups. On the left is placed the population of Tsakones (north: open circles,
south: green dots). On the right are placed the populations of Maniots (Deep Mani, East and West Tayetos.). All the remaining Peloponneseans are clustered
in the center. (c) PCA analysis without the Maniot and Tsakones populations showing a partial separation of the population of Laconia. (d) IBD analysis
illustrating the separation of Peloponneseans in three subpopulations. The color indicates the log10 of the average proportion of genome shared IBD between
individuals in two populations, where higher values (less negative; red color) indicates a higher pairwise proportion of genome shared IBD, and lowervalues
(more negative; yellow color) indicates a lower proportion of genome shared IBD. (e) ADMIXTURE analysis. Notice the distinct structure of the Maniots and
the Tsakones and their clear cut separation from all other Peloponneseans in all values of K.
Genetics of the Peloponnesean Populations
G Stamatoyannopoulos et al
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European Journal of Human Genetics

characteristic patterns of genetic differentiation within Pelopon-
nese, we examine their possible causes and we focus on the
question of the impact of Slavic migrations on the genetic structure
of the Peloponnesean populations. Our results reject the theory of
extinction of medieval Peloponnesean Greeks and their replace-
ment by Slavic and Asia Minor settlers.
SUBJECTS AND METHODS
Design of the study and populations studied
The study has been reviewed by the Institutional Review Board of the
University of Washington and the ethical committees of several provisional
hospitals. We focused on the rural population. We analyzed a total of 241
samples genotyped with the Illumina Infinium Omni 2.5–8 arrays. This is a
Figure 2 Genetic similarity of Peloponneseans, Sicilians and Italians. PCA analysis of several European populations. (a) Notice the north to south distribution
of the populations and that the Peloponneseans are placed to the far right of the graph and overlap with the Sicilians. (b) PCA analysis of Southern European
populations illustrating the close relationship between Peloponneseans Sicilians and Italians (TSI is an Italian population) (c) Network analysis illustrating the
high connectivity between the Peloponnesean populations as well as between the Peloponneseans, the Sicilians and the Italians. Notice the distance
between Peloponneseans and the Slavic, and Near Eastern populations. Peloponneseans are connected with the Near Eastern populations through Crete and
Dodecanese.
Genetics of the Peloponnesean Populations
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novel data set collected under the auspices of our study. Subjects were included
in the study if all four grandparents originated from the same village or from
villages that were o10 kilometers apart. The ages of most participants ranged
between 70 and 90 years (the oldest subject was 107 years old); hence their
grandparents were born between 1860 and 1880. In the 1861 census the
population of Peloponnese was 578 598 individuals. At that time the economy
of Peloponnese was exclusively agricultural and over 85% of the population was
living in small villages and hamlets. We sampled all the districts of Peloponnese
(Figure 1a and Supplementary Table 1) and also focused on two culturally
distinct subpopulations, the Tsacones and the Maniots. To compare the
Peloponneseans with other populations we analyzed samples from published
data sets and data sets generated by our studies (Supplementary Table 2 and
Supplementary Figure 1). Merging genotypes from different sources and quality
control were done as described.11
Identity by descent
The data used for the identity by descent (IBD) analysis were derived from data
sets listed and referenced in Supplementary Table 2. Two individuals share a
genomic segment identical by descent if they have inherited the segment
intact from a common ancestor, without intervening recombination. Allele
strand, reference and alternate alleles were aligned with the 1000 Genomes
European populations (CEU, GBR, TSI, FIN and IBS) using the conform-gt
utility (http://faculty.washington.edu/browning/conform-gt.html) prior to run-
ning Beagle. Marker exclusion criteria were unconfirmed strand orientation,
minor allele frequency o1%, Hardy–Weinberg P-value o10−6,and42%
missing data. After applying these criteria, 560 891 SNPs were used for the IBD
analysis.
We used the Refined IBD algorithm implemented in Beagle 4.1(ref. 12) to
phase the data and infer IBD segments. We set niterations =160 and used
default values for all for all other parameters, including requiring a LOD score
of 3, which means that the probability of the observed genotype data for a pair
of samples in the inferred IBD segment is at least 1000 times greater under an
IBD model than under a non-IBD model. Based on the software recommenda-
tions and marker density, we set ibdtrim =22. We used the HapMap genetic
map to infer genetic length and excluded IBD segments with length o2cM,
since refined IBD has a low false-positive rate when using this threshold.12
R13 was used to generate plots and summarize IBD distributions. The heat
map summarizes average pairwise IBD between chromosomes from different
individuals in the populations being compared (see footnote 4 in
Supplementary Table 3 for details), where higher average pairwise IBD indicates
a closer genetic relationship between populations.
Principal Component Analysis (PCA)
We used Eigenstrat14 as well as our own MatLab implementation of PCA.15,16
Estimating population admixture
We used the ADMIXTURE v1.22 software for all our admixture analyses.17
Cross validation errors of ADMIXTURE analysis ranged between 0.42–0.47
(Figure 1e), 0.55–0.58 (Figure 2c) and 0.56–0.62 (Figure 4d) with smaller error
at K=2.
Quantitative analysis of ADMIXTURE output
Given a target population X and reference populations Y, Z and so on, we were
interested in quantifying the amount of ancestry of population X that is
captured by populations Y, Z and so on. Towards that end we devised a new
approach to quantitatively analyze the output of ADMIXTURE. Recall that
ADMIXTURE, for a particular value of K, will represent each sample using K
coordinates. Thus, for a particular value of Kand for a particular population Y
with nsamples, we can represent the output of ADMIXTURE for this
population as an n-by-Ktable. Then, for each reference population Y, we
summarize this n-by-Kmatrix using its top right singular vector only; in all our
analyses, the top singular value corresponding to the top right singular
vector captured at least 80% of the reference population variance as represented
by ADMIXTURE. Let vYbe the top right singular vector (a K-dimensional
vector) for population Y; similarly, let vZbe the top right singular vector
(a K-dimensional vector) for population Z and so on. Now that we have
represented the ADMIXTURE output for each population as a K-dimensional
signature vector, we can apply standard vector space calculus in order to answer
our original question: how much of the ancestry of population X is captured by
population Y, or population Z and so on. More specifically, in order to
compute the percentage of the ancestry of population X that is captured by
population Y, we compute the percentage of the norm of VXthat is captured
(in projection sense) by vY. Formally, we compute
jVXvYvþ
YVxj


F=jjVXjjF
which returns a value between zero and one. In the above, VXdenotes the
m-by-Kmatrix representing the m samples of population X with respect to
the Kcoordinates returned by ADMIXTURE. The notation vþ
Yindicates the
pseudoinverse of the vector vY, which is equal to the transpose of the vector vY,
suitably normalized. It is also worth noting that the norm used in the above
equation is the standard matrix Frobenius norm. In order to quantify the
amount of ancestry of population X that is captured by both populations Y and
Z, we form the K-by-2 matrix V=[vYvZ] whose columns are the vectors vYand
vZand we compute
jVXVVþVxjjF=jVXjjF





In the above equation, V+denotes the pseudoinverse of the matrix V;the
matrix VV+is a projector on the subspace spanned by the column space of V.
Thus, we basically extract from the matrix VXthe part of VXthat is captured by
the (subspace spanned by the) vectors vYand vZ.
Network analysis
To better visualize and understand the connection between the populations
included in our study, we performed a network analysis on the results of
ADMIXTURE, using a method presented in reference.11
RESULTS
The substructure of the Peloponnesean populations
On PCA analysis the populations are arranged in the form of an
inverted capital letter V (Figure 1b). The left of this formation is
occupied by the population of Tsakones who inhabit the east slopes of
Mount Parnon and the adjacent costal area (Figure 1a). The right of
the formation is occupied by the populations of Maniots who inhabit
the east and west slopes of mount Tayetos and the southern area
of the promontory, the so called Deep Mani (Figure 1a). All other
Peloponneseans cluster in the tip of the letter V (Figures 1b and c).
The ADMIXTURE analysis of Figure 1e shows that the Maniots and
Tsakones are clearly separated from each other and from all other
Peloponnesean populations. Correlations between geographic coordi-
nates and the two principal components (Table 1) are compatible with
Table 1 Correlations between geographic coordinates and principal
componentsa
Populations Latitude correlation Longitude correlation
All Peloponnese 0.50 (PC1) 0.41 (PC2)
Peloponnese minus Tsakonia and Mani 0.49 (PC1) 0.09 (PC2)
Arcadia 0.60 (PC1) 0.12 (PC2)
Laconia 0.45 (PC1) 0.07 (PC2)
Ionian Sea Coast 0.31 (PC2) 0.06 (PC1)
Elis 0.17 (PC1) 0.10 (PC2)
Arcadia and Messenia 0.34 (PC2) 0.16 (PC1)
Arcadia and Laconia 0.36 (PC2) 0.20 (PC1)
Deep Mani 0.15 (PC2) 0.21 (PC1)
East Tayetos and Deep Mani 0.67 (PC1) 0.10 (PC2)
West Tayetos and Deep Mani 0.73 (PC1) 0.42 (PC2)
aThe respective principal component is indicated in parenthesis.
Genetics of the Peloponnesean Populations
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European Journal of Human Genetics

gradients in gene frequencies from north to south across all
Peloponnese, along the Ionian coast, across Arcadia, as well as within
Laconia and between the slopes of Tayetos and Deep Mani.
IBD analysis (Figure 1d) confirms the existence of distinct
Peloponnesean subpopulations. In the populations of Maniots,
individuals share on average 0.25% of their genome (or 35–
36 cM) identical by descent, with 95% of pairs of individuals
sharing at least one IBD segment (Supplementary Table 3).
Similarly, the two Tsakones populations have a very high average
pairwise IBD sharing of 0.66% of their genome, or 94 cM; every
pair of individuals shares at least one IBD segment. Laconia is fairly
closely related to both Deep Mani and to the Tsakones, based on
the darker blue for those pairings in the heat map of Figure 1d. The
heat map also revealed a larger separation between the southern
and northern Peloponnesean populations, with the populations of
Arcadia, Messenia, Elis, Achaea, Corinthia and Argolis forming
their own subgroup. Corinthia and Argolis are the most strongly
related (by IBD) of this subset of populations, sharing nearly 10 cM
IBDonaverage.
Genetic similarity with Sicilians and Italians
As anticipated from the results of previous studies,18–20 the Pelopon-
neseans are genetically placed very close to the Sicilians and Italians
(Figures 2a and b) but they differ from several other populations we
compared them (see Supplementary Figure 2). Network analysis
(Figure 2c), highlighted the interconnections of Peloponnesean
populations as well as the connections between Peloponneseans,
Italians and Sicilians; in this network analysis, Sicilians and Italians
serve as a bridge between Peloponneseans and other European
populations (Basque, Andalusians and French). Slavic populations
are placed far away from the Peloponneseans as are the Near Eastern
populations. The latter are connected to the Peloponnesus via the
islands of Crete and the Dodecanese.
Testing the theory of extinction of the medieval Peloponnesean
Greeks
This theory allows a specific prediction about the genetic ancestry of
the Peloponneseans: the great majority, if not all, of Peloponnesean
ancestry should be Slavic. We compared, the Peloponneseans (except
K=2
K=3
K=4
K=5
K=6
K=7
K=8
Figure 3 Testing the theory of replacement of medieval Peloponesians by Slavs and Asia Minor settlers. (a) PCA analysis shows the broad separation of
Peloponneseans from four populations of the Slavic homeland (Ukrainians, Polish, Russians and Belarusians). (b) PCA comparisons of the Peloponneseans
with three Greek-speaking Asia Minor populations shows only partial overlap with the population of the Asia Minor Aegean coast. (c)ADMIXTUREanalysis
illustrates the wide separation of Peloponneseans from the Slavs in all values of K.
Genetics of the Peloponnesean Populations
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for Maniots and Tsakones) with populations of the Slavic homeland
from which the sixth century Slavs should have originated. The exact
location of the Slavic homeland is debated7,8 butitisplacednorthof
Danube,7between the Oder and Dnieper rivers and includes areas
inhabited by Polish, Ukrainian, Russian and Belarusian populations.
PCA analysis showed a clear separation of Peloponneseans from the
Slavic populations (Figure 3a). By ADMIXTURE analysis (Figure 3c)
the Peloponneseans and the Slavic populations form separate clusters
with a small degree of gene flow from the Slavic to the Peloponnesean
cluster.
Fallmerayer hypothesized that the Hellenization of the Peloponne-
sean Slavs was accelerated by the transfer to the Peloponnese of
Hellenized populations from Asia Minor.9We tested this hypothesis
by comparing the Peloponneseans with three Greek-speaking popula-
tions of Asia Minor: a western-coastal population sample extending
from the Propontis in the north to Alikarnassos (Bodrum) in the
south; a northern population from Pontus, that is, the coast of Black
Sea and the Asia Minor interior corresponding to the current northern
Turkey; and a central Anatolian population from Cappadocia. All
these populations are separated from the Peloponneseans by PCA
(Figure 3b). The small degree of overlap between Peloponnese and the
population of the Asia Minor coast (Figure 3b) is expected for
neighboring Greek populations. The Byzantines frequently moved
Armenians to achieve political objectives21 and Fallmerayer proposed
that Armenians were included in the populations transferred to
Peloponnese by the Byzantines. Peloponneseans differ from the
Armenians by PCA and ADMIXTURE analysis (Supplementary
Figure 3). Collectively, these results are incompatible with the theory
of extinction of the medieval Peloponneseans and their replacement by
Slavic and Asia Minor settlers.
The medieval ancestry of the populations of Mani
The Maniots differ from all other Peloponneseans by PCA (Figure 1b)
and ADMIXTURE (Figure 1e) analysis. They also differ from main-
land, island and Asia Minor Greek populations (data not shown) and
from all the other populations of Supplementary Figure 4, which have
been compared by PCA analysis, but they partially overlap with the
Sicilians and the Italians.
In his treatise on the administration of the Byzantine Empire,22 the
Emperor Constantin Porphyrogenitus describes how two Slavic tribes,
K=2
K=3
K=4
K=5
K=6
K=7
K=8
Figure 4 Testing the hypothesis of Slavic origin of culturally distinct Peloponnesean populations. PCA comparisons of (a) The Maniots of Deep Mani (b)The
Maniots of Tayetos (c) The Tsakones, with populations of the Slavic homeland (Ukrainians, Polish, Russians and Belarusians). Notice the broad separation
between the Slavs and the Peloponnesean populations. (d) ADMIXTURE analysis shows the complete separation of Maniots and Tsakones from the Slavs in
all Kvalues.
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the Mellingi and the Ezeritae, were forced by the Byzantines to
withdraw to the slopes of Tayetos. The Mellingi continued to be
mentioned in the Peloponnesean history untill the 15th century.23
Because of the writings of Porphyrogenitus we sampled separately
the populations of the East and the West slopes of the Tayetos and the
Deep Mani. By PCA (Figure 4a) and ADMIXTURE (Figure 4d) the
populations of Tayetos are distinct from the populations of the Slavic
homeland. Fallmerayer argued that the inhabitants of Deep Mani are
of Slavic origin.9PCA (Figure 4b) and ADMIXTURE (Figure 4d)
analyses makes this hypothesis unlikely.
As an alternative origin of the Maniots, Fallmerayer proposed that
they are descendants of Mardaites.9This medieval warrior tribe used
to inhabit the mountainous regions between Asia Minor and Syria
but in late seventh century CE was resettled by the Byzantines in
Asia Minor and other areas of the Empire.24 The Mardaites have
disappeared from history but oral tradition claims that they are the
ancestors of the Maronites of Lebanon, although this claim has been
disputed.25 PCA and ADMIXTURE analyses failed to show any close
relationship between Maniots and the Maronites (Supplementary
Figure 5).
The question of Slavic ancestry of Tsakones
The Tsakones of the eastern slopes of Mount Parnon differ from all
other Peloponneseans (Figures 1b and e) and from all other popu-
lations of Supplementary Figure 6 we have compared them. They used
to speak a dialect of Doric origin26 which was not comprehended by
the other Peloponneseans. Their name was considered by medieval
authors to represent a corruption of the word Lacones (Tsakones =
Lacones). Fallmerayer argued against a Doric origin of the Tsakones
and, instead, proposed that they were the descendants of a Slavic tribe
that had migrated to Peloponnese before the flood of the Slavic settlers
reached the peninsula. PCA (Figure 4c) and ADMIXTURE (Figure 4d)
analyses argue against this hypothesis.
Quantitative assessment of the ancestry of Peloponneseans
To quantify the findings of the ADMIXTURE analyses, we employed a
method for the meta-analysis of the ADMIXTURE output that treats
the output as a set of vectors in a K-dimensional space (for a particular
value of Kbetween four and eight). Each population is then
summarized by a single vector (using PCA) and vector space calculus
is used in order to identify the percentage of ancestry of a target
population that is captured by one or more reference populations.
Notice that our choice to summarize each population by a single
vector is akin to computing the mean ADMIXTURE output for a
particular population. In most cases, ADMIXTURE returns a homo-
genous structure for a particular population and thus the top principal
component is a good summary of the sample vectors returned by
ADMIXTURE.
First we focused on the ADMIXTURE analysis of Figure 3c which
includes seven Peloponnesean populations (Argolis, Corinthia,
Achaea, Elis, Arcadia, Messenia and Laconia), four Slavic populations
(Belarusians, Russians, Polish and Ukrainians), three Southern
European populations (Italians, Basque and Andalusians) and the
French. The results of Table 2 show that there is considerably more
shared ancestry between the Peloponneseans and the French, Anda-
lusians and Italians compared to the shared ancestry between the
Peloponneseans and the Slavic populations. The average shared
ancestry with French ranges from 39 to 42%; with Andalusians from
53 to 62%; and with the Italians from 85 to 96%. In contrast, the
average shared ancestry with the Slavic populations is always o15%.
Therefore, the Peloponneseans are genetically much more distinct
from the Slavic populations and are much more similar to Southern
European populations. We also observe that the Basques, (a popula-
tion that is well-known to be isolated and genetically different from
even its neighboring Iberian populations) are very distinct from all
populations in our analysis. This is precisely why we included them in
these ADMIXTURE meta-analyses: on average Basques share o4% of
common ancestry with any Peloponnesean population. Notice that
this number is relatively close to the average ancestry shared between
the Peloponnesean populations and the Belarusians, Polish and
Ukrainians. All these populations share between 5.2 and 8.5% of
common ancestry with the Peloponnesean populations. These Slavic
populations are, from a genetic perspective, approximately as far apart
from the Peloponneseans as are the Basques.
Table 2 Shared ancestry between Peloponnesean populations and Slavic, Italian and other European populationsa
Belarusians Russians Polish Ukrainians French Italians Basque Andalusians
Argolis 5.4 (1.5) 12.2 (1.2) 5.8 (0.8) 6.8 (1.1) 39.1 (19.2) 94.7 (4.8) 2.8 (1.4) 60.5 (5.9)
Corinthia 5.9 (1.7) 13.0 (1.3) 6.3 (1) 7.5 (1.3) 41.2 (18.5) 94.9 (4.0) 3.1 (1.7) 62.0 (5.9)
Achaea 6.5 (1.7) 13.8 (1.1) 7.0 (0.8) 8.1 (1.1) 41.4 (18.4) 94.8 (4.0) 2.7 (1.4) 61.3 (5.8)
Arcadia 5.3 (1.8) 10.9 (2.4) 5.2 (1.2) 6.2 (1.5) 39.1 (18.2) 85.4 (14.6) 2.4 (1.4) 53.8 (9.1)
Elis 6.1 (1.3) 13.1 (1.2) 6.5 (0.8) 7.6 (1.1) 41.4 (18.3) 95.0 (3.3) 3.3 (1.7) 61.6 (5.6)
Messenia 6.7 (1.7) 14.4 (1.2) 7.3 (0.9) 8.5 (1.2) 42.6 (18.4) 95.2 (4.0) 2.7 (1.3) 61.8 (5.7)
Laconia 4.8 (1.2) 11.4 (1.5) 5.2 (0.9) 6.4 (1.1) 41.1 (14.6) 96.1 (2.3) 2.3 (1.4) 59.8 (5.6)
aThe first number for each pair of populations indicates the average shared ancestry for values of Kbetween 4 and 8, while the number in parenthesis indicates the s.d.
Table 3 Shared ancestry between the populations of Mani and Tsakonia and Slavic, Italian and other European populationsa
Belarusians Russians Polish Ukrainians French Italians Basque Andalusians
Deep Mani 0.7 (0.1) 1.6 (0.7) 0.9 (0.4) 1. 0 (0.3) 6.4 (3.5) 25.3 ( 21.7) 0.3 (0.2) 7.6 (5. 1)
West Tayetos 4.9 (5.1) 8.6 (6.9) 6.8 (5.4) 6.5 (5.7) 16.4 (12.7) 41.5 (32.5) 0.6 (0.5) 15.2 (11.1)
East Tayetos 5.7 (3.4) 10.9 (4.0) 7.9 (3.7) 8.0 (3.7) 27.7 (4.8) 58.0 (20.7) 2.0 (1.4) 27.0 (4.3)
North Tsakonia 3.9 (1.7) 8.2 (2.1) 5.0 (2.2) 6.0 (2.2) 26.7 (3.5) 51.2 (4.6) 1.5 (1.1) 26.9 (3.5)
South Tsakonia 0.2 (0.0) 0.9 (0.4) 0.4 (0.1) 0.6 (0.2) 4.1 (2.9) 14.2 (11.0) 0.2 (0.1) 5.3 (3.8)
aThe first number for each pair of populations indicates the average shared ancestry for values of Kbetween 4 and 8, while the number in parenthesis indicates the s.d.
Genetics of the Peloponnesean Populations
G Stamatoyannopoulos et al
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European Journal of Human Genetics

We next determined the shared ancestry between the five distinct
Peloponnesean populations (Deep Mani, West and East Tayetos,
North and South Tsakonia), the Slavs, the southern European
populations, the French and the Basque. The ADMIXTURE plot of
Figure 4d and the data of Table 3 show that the amount of shared
ancestry between these five Peloponnesian populations and the
Slavic populations is very low. The ancestry Deep Mani shares with
Belarusians, Polish and Ukrainians ranges from 0.7 to 1.0%. East and
West Tayetos share from 4.9 to 8.6% ancestry with the three Slavic
populations which is five to eight times higher than that of Deep Mani
but lower to the ancestry the other Peloponnesans share with the Slavs.
Slightly lower, compared to the other Peloponneseans, is the ancestry
shared between West/East Tayetos and the Russians (8.6–10.9%). The
ancestry North and South Tsakonia shares with the Slavs ranges from
4 to 8% and 0.2 to 0.9%, respectively. Compared to the very low
ancestry shared with the Slavs, South Tsakonia and Deep Mani share
14 and 25% ancestry with the Italians. North Tsakonia, East and West
Tayetos share from 41 to 57% ancestry with the Italians. Again, the
Basques are isolated from the five Peloponnesean populations.
DISCUSSION
Our analysis of the genetic ancestry of the Peloponnesean populations
and their relationships with the Slavs and other Europeans settles a
historical controversy that has persisted for over 170 years. This
controversy illustrates the problems historians face in their efforts to
reconstruct population history on the basis of inadequate written
sources. Fallmerayer based his theory of extinction of the medieval
Peloponnesean Greeks on the writings of few early and two middle-
medieval Byzantine authors. The early sources were very short
comments in texts of 6th and 7th century historians and ecclesiastic
authors.9The middle-medieval documents were a letter by an eleventh
century Patriarch of Constantinople and the writings of tenth century
Emperor Constantine Porphyrogenitus. Fallmerayer’stheorycreated
sensation among historians. An early rebuttal was published by the
Greek historian Paparrigopoulos27 who examined the same sources
Fallmerayer have used to construct his theory and reached different
conclusions, that is, that the Slavs did not reach the Greek proper
during the sixth century and, when they arrived, they did not slaughter
the local population. The many historians who have contributed to the
very extensive literature on this topic during the last century (partially
summarized in Curta10 and Zakythenos28) usually either accept or
reject the theory of extinction of the Peloponnesean Greeks. It seems
that personal philosophies influence the historians’judgment. Fall-
merayer was an educator and journalist turned historian, a liberal
intellectual for his time and a slavophobe who feared the increasing
influence of Russia in the Balkans at the expense of the Ottoman
Empire. Paparrigopoulos was a Greek historian who was promoting
the idea of the continuity of the Greek ethnicity during the medieval
period. The findings of our study settle these issues and provide a
direct test of the theory of the extinction of the medieval Peloponne-
sean Greeks. It is clear that the Slavs settled in Peloponnese, as the
quantitative measurements of Slavic ancestry indicate (Tables 2 and 3).
It also seems that their numbers were relatively small compared to the
size of the local population as the low levels of Slavic ancestry of the
Peloponnesean populations indicate.
In his book on the Administration of the Empire22 Constantin
Porphyrogenitua describes the wars between the Byzantines and two
Slavic tribes, who initially had settled the lowland Laconia but were
forced to withdraw to the security of the slopes of the mount Tayetos,
in order to avoid subjugation to Byzantine rule. Porphyrogenitus tells
us that the slopes of Tayetos were Slavic lands; however, our analyses
show low levels of Slavic ancestry in the populations of Tayetos.
The most reasonable interpretation for the discrepancy between
the medieval text and the genetic data is that the size of the Slavic
settlements in the slopes of Tayetos was small and the Slavic
population was diluted by migrations from Deep Mani during the
subsequent centuries. Despite its inhospitable environment, Deep
Mani was densely populated29 and there is historical evidence for
high mobility and migrations of Maniots.30 Ageneflow path from
Deep Mani to the slopes of Tayetos is also suggested by our PCA
analysis and the correlations between geographic coordinates and
principal components.
The striking difference between the Tsakones and the remaining
Peloponneseans on PCA and ADMIXTURE analysis can be attributed
to isolation by distance. Geographic isolation explains the retention of
their dialect. In ancient times the land of Tsakones, then called
Cynouria, was inhabited by Doric speaking Ionians6and because of its
geography was most likely isolated from the other Peloponneseans.
Isolation by distance is also the likely explanation of the findings in the
populations of Mani. Porphyrogenetus in his writing about the Slavs
of Tayetos also asks what happened to the ancient inhabitants of
Laconia, the Hellenes, who continued to adhere to the ancient Greek
religion.22 He finds them withdrawn in the inhospitable, agriculturally
poor and rocky area of southern Tayetos, the area which we refer to
here as the Deep Mani. Ancient DNA studies could perhaps test
whether there is any relationship between Maniots and ancient Lacons
or between Tsakones and ancient Ionians.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
ACKNOWLEDGEMENTS
This study was supported with funds from the Lucille P Markey Charitable
Trust to GS; National Science Foundation grants to PD; Altius Institute for
Biomedical Sciences to JS; ARISTEIA II Programme and NSRF 2007–2013
grant to PP; and NIH HG008359 grant to BLB. AP was supported by the NSF
Graduate Research Fellowship Program DGE-1256082. The content is solely the
responsibility of the authors and does not necessarily represent the official views
of the National Institutes of Health. We wish to thank the following physicians
and health center personnel for their invaluable help during the field study.
Arcadia: P Bourtzoukli, Argolis: D Kostakis, P Kambosos, E Spyropoulou,
Achaia: N Razis, A Kouroukli-Symeonidou, S Fokas, P Theodoropoulos,
Corinthia: K Farmaki, E Chaniotakis, P Theodoropoulou, K Karakonstantis,
TLygeros,Elis: D Pavlopoulou, I Lentzos, G Paraskeva, N Choundras,
H Arvanitakis, G Stavropoulou, Mani: A Mariolis, P Lykousas, Messenia:
I Adamopoulos, S Hideriotis, M Rentoulis, D Sotiropoulos, Laconia: M Tsironi,
G Sakelariadis, A Vasimbosis, S Arahoviti, S Alevizou, P Andrianopoulos,
Tsakonia:HKontoleon,PPerdicari.
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