Integration versus apartheid in post-Roman Britain: A response to Pattison

Abstract

In this issue, Pattison (2008) questions whether it is necessary to assume an apartheid-like social structure in Early Anglo-Saxon England (Thomas et al. 2006) in order to account for the apparent discrepancy between archaeological estimates of the scale of Anglo-Saxon migration into post-Roman Britain (Harke 2002; Hills 2003) and Y-chromosome-based estimates of the contribution of Germanic settlers to the modern English gene pool (Weale et al. 2002; Capelli et al. 2003). He is mainly concerned with a model mathematically explored by Thomas et al. (2006) but first proposed on historical arguments by Woolf (2004, 2007; but also see Charles-Edwards 1995; Harke 1998). This model assumes that the people of indigenous ethnicity were at an economic and legal disadvantage compared with those having Anglo-Saxon ethnicity—leading to differential reproductive success—and that the two groups were, to an extent, reproductively isolated. Although Pattison questions some of the assumptions of this model, the mainstay of his argument is that the proportion of indigenous British ancestry had been eroded since the pre-Roman period by a series of immigration events that are sufficient in magnitude to explain the genetic estimates of northwest continental European ancestry suggested by Weale et al. (2002; 50–100%) and Capelli et al. (2003; mean of 54%).

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, published 7 November 2008, doi: 10.1098/rspb.2008.0677275 2008 Proc. R. Soc. B
Mark G Thomas, Michael P.H Stumpf and Heinrich Härke
response to Pattison
Integration versus apartheid in post-Roman Britain: a
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Comment
Integration versus apartheid in post-Roman
Britain: a response to Pattison
In this issue, Pattison (2008) questions whether it is
necessary to assume an apartheid-like social structure
in Early Anglo-Saxon England ( Thomas et al.2006)in
order to account for the apparent discrepancy between
archaeological estimates of the scale of Anglo-Saxon
migrationintopost-RomanBritain(Ha¨rke 2002;Hills
2003) and Y-chromosome-based estimates of the
contribution of Germanic settlers to the modern English
gene pool (We a l e et al. 2002;Capelli et al.2003). He is
mainly concerned with a model mathematically explored
by Thomas et al. (2006) butfirstproposedonhistorical
arguments by Woolf (2004,2007; but also see Charles-
Edwards 1995;Ha¨ rke 1998). This model assumes that
the people of indigenous ethnicity were at an economic
and legal disadvantage compared with those having
Anglo-Saxon ethnicity—leading to differential reproduc-
tive success—and that the two groups were, to an extent,
reproductively isolated. Although Pattison questions
some of the assumptions of this model, the mainstay
of his argument is that the proportion of indigenous
British ancestry had been eroded since the pre-Roman
period by a series of immigration events that are
sufficient in magnitude to explain the genetic estimates
of northwest continental European ancestry suggested
by Weale et al.(2002; 50–100%) and Capelli et al.
(2003;meanof54%).
The methodology that Pattison (2008) uses is first to
estimate the scale of various immigration and emigration
events affecting Britain since the Late Iron Age and then to
apply these figures to separate estimates of the size of the
British population in order to generate a curve of the
accumulated immigrant ancestry component over the last
2000 years. He assumes that the British population at the
time of the Roman occupation already included approxi-
mately 5 per cent immigrant ancestry primarily due to an
influx of people of Belgic descent (but see below). Broadly
speaking, he infers an approximately 9 per cent immigrant
ancestry component following Roman occupation, rising
sharply to approximately 18 per cent following the Anglo-
Saxon migration, then rising somewhat more gradually
to approximately 23 per cent by 1750. After 1750, he
infers a more dramatic rise in the immigrant ancestry
component until by 1950 it reaches 36 per cent. Such
inferences, while of interest, are highly speculative and
based mostly on sparse data. But crucially, even if issues
relating to the accuracy of Pattison’s immigration episode
estimates can be put aside (but see below), only a small
fraction are relevant to the model explored by Thomas
et al. (2006) or, more specifically, the Y-chromosome-
based estimates of northwest European ancestry reported
by Weale et al. (2002) and Capelli et al. (2003).
Both genetic studies estimate northwest continental
European ancestry in England and both draw similar
conclusions, but these studies are based on different
approaches. Weale et al. (2002) observed a remarkable
genetic similarity between five central English towns and a
sample from Friesland while also finding striking
differences between the English towns and two Welsh
towns. They attempt to explain this similarity by conserva-
tively assuming (i) genetic identity during the Neolithic and
(ii) continuous gene flow between the ancestral English and
Friesian populations since the Neolithic (set at 0.1% per
generation). Using coalescent simulation, they conclude
that such assumptions (individually or jointly) are insuffi-
cient to explain the observed genetic similarity, and that a
mass migration event in the last 2425 years is required.
Since the Anglo-Saxon migration is archaeologically and
historically the best attested influx that affected England,
but not Wales, in that period, they go on to estimate the
scale of that migration (50–100%). Capelli et al. (2003)
performed a number of analyses on a larger Y-chromosome
dataset. In the one that is relevant for the discussion here,
they estimate admixture proportions using a combined
southern Danish/north German sample and a combined
central Irish/Basque sample to represent the descendants of
Anglo-Saxon and indigenous British populations, respect-
ively. Although they found more regional heterogeneity—
probably as a result of a wider sampling strategy—the mean
southern Danish/north German contribution to the English
gene pool was estimated to be 54 per cent. In both studies
the source of migrants was specified, and in neither study—
as wrongly implied by Pattison (2008)—did they assume
genetic homogeneity in ancestral source populations. By
contrast, Pattison provides an estimate of the total
immigrant contribution to Britain—from any source
population—since the Late Iron Age. While those originat-
ing in the source regions of the Anglo-Saxons (principally
the northern Low Countries, northwest Germany and
southern Denmark) are relevant to his argument and
would go some way to explaining the results of Weale et al.
(2002) and Capelli et al. (2003), any influx originating in
genetically differentiated populations would only serve to
increase the burden of explaining the observed similarity
between England and northwest continental Europe. The
only exception to this is migration that contributes equally
to both England and the northwest continental European
populations studied by Weale et al. (2002) and Capelli
et al. (2003). Additionally, both genetic studies sampled
only men whose respective paternal grandfathers were
born within 30 km of their places of residence, in all
cases small (population of less than 20 000) and long-
established market towns. Such locations are less likely
to be influenced by recent immigration than large cities
Proc. R. Soc. B (2008) 275, 2419–2421
doi:10.1098/rspb.2008.0677
Published online 29 July 2008
Received 19 May 2008
Accepted 1 July 2008
2419 This journal is q2008 The Royal Society
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(Pooley & Turnbull 1996). We note that the most
dramatic change in the proportion of indigenous British
descent in Britain according to Pattison’s model occurs
after 1900 and is thus less likely to influence the results of
the two genetic studies.
Pattison also appears to ignore the serious problems
besetting estimates of relative and absolute numbers of
natives and immigrants from historical and archaeological
data. There are no recorded population figures for Britain
before AD 1086 (Darby 1977;Holt 1987). For all earlier
periods, population estimates are extrapolations from
fragmentary evidence, and such estimates have varied
considerably (Millett 1990;Ha¨ rke 2002). Incidental
reports of numbers of immigrants are notoriously
unreliable, and absolute numbers of immigrants before
the Norman period can only be calculated as a proportion
of the estimated overall population. Pattison’s procedure
of estimating absolute numbers of migrants and then
setting them in relation to the estimated absolute size of
the overall population is, therefore, the wrong way round
and likely to conflate error. Also, Pattison’s model is
deterministic, not stochastic. His forward accumulation
approach would propagate any uncertainty poorly and, as
is well known in population genetics (e.g. Ewens 2004),
the variability of population processes tends to overwhelm
the mean behaviour, which may be atypical. It would
have been more appropriate to incorporate binomial
sampling—as in the model presented by Thomas et al.
(2006)—to quantify some of the uncertainties inherent in
population dynamics. Without a sound probabilistic
framework, we believe, there is no way of assessing the
level of uncertainty in his results.
In addition to the methodological concerns above, we
find a number of problems with the assumptions
underlying Pattison’s model. First, he overstates the case
for a pre-Anglo-Saxon genetic influx from Germanic areas
on the continent. His assumption of a Germanic descent
of the Belgae and their migration into southern England in
the pre-Roman period is based on an outdated hypothesis
(Hawkes & Dunning 1930). The only evidence for their
Germanic origin is the report by an outside observer, Caesar,
who himself contradicts this claim elsewhere with a clear
distinction between Belgae and Germani (von Petrikovits
1999). The ambiguous evidence for their migration to
southern England has been debated for several decades
(since Clark 1966;seeCreighton 2000;Cunliffe 2005). The
only safe conclusion can be that the Belgic migration (if any)
would have added continental ancestry to southern
England, not specifically Germanic ancestry. Concerning
Germanic soldiers in Roman Britain, their proportion has
been overstated in the literature (see Elton 1997). The exact
numbers of Germani in the Roman army are not easy
to estimate because recruitment was by regions, not by
ethnicity (Mann 1983); and some of the figures suggested
by Pattison rely, again, on the fallacious assumption that the
inhabitants of Belgic Gaul were Germanic. And while there
is widespread agreement today that not all Roman army
units left the island in or by AD 407, the units that stayed
behind were probably a few thousand frontier troops
(limitanei), whose composition would have been mixed and
added to by local recruitment ( Holder 1982;James 1984). In
consequence, any ‘Germanic’ genetic contribution into
Britain before the Anglo-Saxon immigration is neither as
certain, nor as substantial, as Pattison argues.
Second, Pattison’s ‘alternative’ historical narrative of
the Anglo-Saxon immigration is based almost entirely on a
single book (Morris 1973) that was considered speculative
and uncritical when it was published 35 years ago (see
Dumville 1977). While one might expect that there was
some cultural borrowing by the immigrants, virtually all
examples quoted by Pattison are doubtful and disputed
hypotheses (continuity of field boundaries; see Rippon
1991), unsupportable ideas (early tribute collection
cannot be documented owing to the absence of written
records before the seventh century; see Whitelock 1979)
and withdrawn claims (continuity of Roman-style animal
husbandry; see Crabtree 1993). Furthermore, on current
evidence it is not possible to demonstrate the ‘gradual
blending’ of British and Anglo-Saxon cultures suggested
by Pattison, since in the fifth/sixth centuries AD the
archaeological evidence in England shows only one
culture, that of the Germanic immigrants, because that
of the native Britons had become invisible even before the
immigrants started to arrive in substantial numbers
(Ha¨ rke 2007). We note, however, that Pattison, notwith-
standing a different perspective, agrees with our own
estimate of the numbers of Anglo-Saxon immigrants.
Third, it is difficult to see how the author could have
derived his reinterpretation of the late seventh century
Laws of Ine from the original text. Britons are mentioned
in several clauses; with one exception, they are mentioned
as being in a subordinate role or of slave status; and in the
one clause where ‘free’ Britons are mentioned, the
monetary value of their lives (the wergild) is set at half
that of their Saxon equivalents (Whitelock 1979). Even
the testimony of a Briton in court is rated only half that
of a Saxon witness. These provisions reflect a society
systematically divided along ethnic lines; the historian
Charles-Edwards (1995) has called it ‘a polity of two
nations’, and a new sociolinguistic analysis by German
(Thomas et al. 2008) fully supports this interpretation.
While such ethnic and legal distinctions might ‘encourage
integration’ (as Pattison claims), the laws themselves do
not offer such a route: there are no provisions for Britons
becoming Anglo-Saxons.
Fourth, in the case of our evidential argument from
skeletal data, Pattison confuses starting assumptions and
conclusions. The original argument did not ‘assume’ that
burial with weapons was an almost exclusively Anglo-
Saxon (i.e. immigrant) rite: it concluded that from a
detailed analysis of all available skeletal and archaeo-
logical data of male burials with and without weapons in
fifth- to seventh-century cemeteries, after alternative
explanations of the skeletal differences between the two
male groups had been discussed and dismissed. The full
stature argument is contained in a German-language
book (Ha¨ rke 1992), which Pattison does not cite; he
relied instead on the short summary in an English article
(Ha¨ rke 1990).
We accept Pattison’s criticism of our use of the term
‘intermarriage’. This term is somewhat euphemistic, and
‘interbreeding’ would have been more appropriate.
However, we do mention that ‘forced extra-marital matings
are also likely to have occurred’ ( Thomas et al. 2006).
In summary, we find Pattison’s (2008) argument,
while persuasively written, to be wanting in terms of
methodology, data sources, underlying assumptions and
application. We conclude that for now an apartheid-like
2420 M. G. Thomas et al. Comment. A response to Pattison
Proc. R. Soc. B (2008)
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social structure is supported by historical and archae-
ological evidence and remains the most plausible model
to explain the high degree of northwest continental
European male-line ancestry in England.
The authors wish to thank John Creighton (Reading), Simon
James (Leicester) and Hella Eckardt ( Reading) for infor-
mation on the current state of the debate on pre-Roman and
Roman populations in Britain.
Mark G. Thomas
1,
*, Michael P. H. Stumpf
2
and Heinrich Ha¨rke
3
1
Department of Genetics, Evolution and Environment,
University College London, Wolfson House,
4 Stephenson Way, London NW1 2HE, UK
2
Centre for Bioinformatics, Imperial College London,
Wolfson Building, London SW7 2AZ, UK
3
Department of Archaeology, The University of Reading,
Whiteknights, Reading RG6 6AB, UK
*Author for correspondence (m.thomas@ucl.ac.uk).
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