*The Centre for Genetic Anthropology, Departments of Biology and Anthropology, University College London, University of London;
Department of Anthropology, University of California, Davis;
Faculteit Biologie, Vrije Universiteit, Amsterdam, The Netherlands
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The use of migration as an explanation for cultural transitions has varied greatly over the past 100 years and remains controversial (Clark 1966
; Chapman 1997
; Burmeister 2000
; Shennan 2000
). Before the 1960s, archaeological evidence for cultural change (such as changes in pottery type) was often interpreted as prima facie evidence for substantial immigration. The processual school or New Archaeology that emerged in the 1960s and 1970s rejected this view, arguing firstly that the adoption of new cultures could occur through trade or by the influx of a small ruling elite with minimal or no impact on the gene pool (the "elite dominance" model of Renfrew [1987
]) and secondly that if no positive evidence for migration could be found then explanations based on nonmigrational internal forces were more parsimonious and therefore preferable (Adams 1968
; Adams, Van Gerven, and Levy 1978
). More recently, this antimigrationist stance has been questioned (Anthony 1990
; Härke 1998
) and migrational models reconsidered (e.g., Chapman and Hamerow 1997
; Burmeister 2000
).
These changes in archaeological opinion have had a particular impact on interpretations of cultural transitions in Britain (Clark 1966
). Because of its geographical location on the northwestern edge of Europe, migrations and invasions from the continental mainland were once considered to be the obvious explanation for cultural transition (e.g., Hawkes and Hawkes 1942
). Today, cultural changes before the Roman invasion, which are for the most part lacking in historical records, are no longer interpreted as automatically implying migration, and for these changes the role of migration remains unresolved. For cultural transitions after the Roman invasion, historical records argue against large migrations coinciding with either Roman occupation or the Norman Conquest, and the prevailing view is therefore that these later events represent examples of elite dominance (Kearney 1989
; Davies 1999
). Historical and archaeological research argue for some degree of Viking settlement in both East Anglia and the Midlands in the 9th century a.d. but against a substantial displacement of the existing people during this period (Richards 2000)
.
Today, the most hotly debated of all the British cultural transitions is the role of migration in the relatively sudden and drastic change from Romano-Britain to Anglo-Saxon Britain (Hamerow 1997
; Burmeister 2000
). This transition was once widely accepted as providing clear evidence for a mass migration from continental Europe and the near-complete replacement of the indigenous population in England (Leeds 1954
; Myres 1986
). Stories of migration are included in the writings of Gildas (ca. a.d. 540) and Bede (a.d. 731) and hinted at in Anglo-Saxon sagas, such as Beowulf (Davies 1999
). Archaeological evidence confirmed a rapid rise of continental culture in England (Esmonde-Cleary 1993
) and suggested a contemporaneous desertion of continental Germanic settlements. More recently, however, authors have questioned the evidence for large-scale immigration (Crawford 1997
; Hamerow 1997
) and continental emigration (Näsman 1988
; Petersen 1991
) and emphasized the continuity of the Romano-British population in England. The sudden change to an Anglo-Saxon culture has been attributed instead to rapid acculturation and indigenous developments, with only a small number of Germanic immigrants (perhaps a male military elite) settling in Britain (Arnold 1984
; Hodges 1989
; Higham 1992
). The contribution of Anglo-Saxon immigration to the modern English gene pool thus remains uncertain.
Genetic data comprise an obvious source of information to help resolve these issues. Previous studies examining biological variation in Britain have identified various patterns of genetic variation. These include studies on blood groups (Bodmer 1993
; Mascie-Taylor and Lasker 1996
), serum proteins and isoenzymes (Cartwright, Hargreaves, and Sunderland 1977
; Mastana et al. 1993
), HLA genes (Papiha, Duggan Keen, and Rodger 1985
; Bodmer 1993
), and multiple classical genetic markers (Falsetti and Sokol 1993
; Cavalli-Sforza, Menozzi, and Piazza 1994
; Mastana and Sokol 1998
), as well as on patterns of disease incidence, such as phenylketonuria (Tyfield, Osborn, and Holton 1997
), multiple sclerosis (Poser 1994
), skin cancer (Long, Darke, and Marks 1998
), and haemochromatosis (Merryweather-Clarke et al. 1997
). These data have been interpreted as reflecting historical migrations and settlement patterns, but formal testing of alternative migratory models has not been attempted.
The nonrecombining portion of the Y chromosome and the mitochondrial genome are useful sources of data because they provide exceptionally detailed high-resolution haplotypes, allowing fine definition of the underlying gene genealogies. The Y chromosome, which is much larger, is particularly useful because it has many slowly mutating biallelic markers to help resolve genealogical clades as well as rapidly mutating microsatellite markers to aid in the dating of very recent events (Thomas et al. 1998
; Kayser et al. 2001
). The extra information provided by these high-resolution haplotypes facilitates the fitting of population genetic models. Although the resulting demographic inferences are based on only a single locus, increasing the effects of evolutionary variance derived from chance differences in the genealogy, such systems are still useful because they are the only ones that allow sex-specific demographic inferences to be made.
Previous studies of mtDNA and Y chromosome variation across Europe have reported evidence of Paleolithic and Neolithic expansions reflected in large-scale clines (Torroni et al. 1998
; Casalotti et al. 1999
; Hill, Jobling, and Bradley 2000
; Malaspina et al. 2000
; Richards et al. 2000
; Rosser et al. 2000
; Semino et al. 2000
; Simoni et al. 2000
), but these studies did not consider the effects of historical migrations on more local patterns of genetic variation. Helgason et al. (2000)
examined Y chromosome and mtDNA variation in the modern Icelandic population to assess the relative proportions of Scandinavian and Celtic ancestry stemming from historical migrations, whereas Wilson et al. (2001)
compared Y chromosome, X chromosome, and mtDNA variation in eight population samples (including the Llangefni, Norway, and Friesland samples reported here) to investigate genetic changes associated with cultural transitions in North Wales and Orkney, two areas at the fringes of the British Isles. Through a comparison of signature haplotypes, Wilson et al. (2001)
found evidence for Celtic male ancestry in the North Welsh and/or both Celtic and Scandinavian (Viking) male ancestry in the modern Orcadian population. Further comparisons of these British samples with Basque data suggested that the male Celtic genetic component was Paleolithic in origin, and therefore, that subsequent cultural transitions in North Wales were not associated with substantial incoming male gene flow. However, the study of Wilson et al. did not directly address the effects of cultural transitions in other areas of Britain.
This study is the first to analyze data from an east-west transect across Central England and North Wales to evaluate evidence of male population migration under a wide range of flexible population genetic models. Samples were collected in seven towns along this transect, and a combination of slowly evolving biallelic markers (so-called Unique Event Polymorphisms or UEPs) and rapidly evolving microsatellites on the Y chromosome were typed to look for evidence of local or small-scale genetic transitions. We compared the data with samples from Friesland and Norway to look for evidence of male immigration from the continent. In addition to comparing signature haplotypes among population samples, we applied novel model-based methods to make inferences about both the possible timing and extent of male continental migration into Central England.
![]() |
Materials and Methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
|
We explored population genetic models that could explain our data using two methods of inference. The first method involved full-likelihood Bayesian inference of genetic and demographic parameters under population splitting and growth using the BATWING program (URL: http://www.maths.abdn.ac.uk/ijw), extended from the Markov chain Monte Carlo (MCMC) algorithm presented by Wilson and Balding (1998)
. Microsatellite mutation likelihoods were calculated using an unbounded symmetric stepwise mutation model. The priors chosen for major BATWING parameters are summarized in table 1
. Locus-specific priors for the mutation rate per generation were based on observed mutations for these loci, as reported in Heyer et al. (1997)
, Bianchi et al. (1998)
, and Kayser et al. (2000)
, combined with a standard exponential pre-prior. As a precautionary measure, DYS388 was excluded from BATWING analysis (and also from the Monte Carlo likelihood method described later) because no published data on observed meioses are available for this locus, and therefore, no direct verification exists of stepwise mutation behavior. Unique-event mutations inferred from binary marker data were used to condition the possible trees but otherwise did not contribute to the likelihood. Population splitting was modeled under strict fission with no subsequent background migration. Population growth was modeled as an exponential from an initially constant effective population size. Weakly informative priors were given to other parameters to aid in the convergence of the MCMC process. The prior for initial effective population size covers the values commonly assumed for the global Y chromosome effective population size as well as lower values to compensate for this being a regional sample and for representing the effective size before growth. The prior for population growth rate per generation is very flat and gives support to a very wide range of possible values (extending beyond the 2.5% and 97.5% quantiles) to reflect the uncertainty in relating growth in effective population size to growth in real (census) population size. All other parameters, such as the start-of-growth date and the population split dates, were given flat, uninformative priors.
|
Confidence intervals (95%) for the remaining parameters TS, m, TF, and F describing population differentiation were estimated by setting constant values for all but one of the parameters and finding the upper and lower limits for the remaining parameter of interest. Preset values for the split date TS were chosen to reflect one of the three scenarios: (1) Island model (TS = ), (2) Neolithic (TS = 240 generations BP or 6,000 years BP assuming 25 years per generation), and (3) Anglo-Saxon (TS = 60 generations BP or 1,500 years BP assuming 25 years per generation). Preset values for the background migration rate m were set at one of two extremes: (1) an implausibly low value of m = 0, and (2) an implausibly high value of m = 0.1%. The latter value is estimated from migration statistics to and from the European Economic Area as a whole over the past 25 years (source: http://www.homeoffice.gov.uk/rds/index.htm). We regard this as a figure well in excess of realistic values for continuous background migration both because it is based on figures for the whole of Europe (i.e., not just Friesland) and because we expect background migration in recent times to be very high as a result of modern trends in communication and travel. In models that included the parameters F and TF, F was always the parameter of interest and TF was set under an Anglo-Saxon scenario (TF = 60).
Confidence limits (95%) for the parameter of interest were found using RST as a summary statistic of population differentiation, such that 2.5% of the simulated RST values were equal to or more extreme than the observed RST value when the parameter was set at one of the two limits, based on 10,000 Monte Carlo iterations of the coalescent simulation. Confidence limits were determined to an accuracy of the least significant digit stated. We also obtained confidence limits using (µ)2 rather than RST as the summary statistic (Goldstein et al. 1995
) and found these to be similar although generally wider than those obtained using RST.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
|
|
|
|
|
|
Thirdly, no significant differences in haplotype frequencies exist between Friesland and any of the Central English towns. Comparisons between Norway and the Central English towns, on the other hand, are all significant, apart from Bourne (P = 0.237), which may be explained by the small number of samples collected from this town (n = 12). Furthermore, bootstrap tests on RST values revealed that the Central English (all five towns combined) are significantly more closely related to the Frisians than they are to the North Welsh (Llangefni: P < 0.001; Abergele: P = 0.046) or to the Norwegians (P = 0.005). Both Friesland and Norway are significantly different from the North Welsh towns. Similar results were obtained using FST values based on haplogroup frequencies, but tests on FST values based on haplotype frequencies were not significant because of the large number of singletons at this level. Taken together, these results suggest considerable male-line commonality between Central England and Friesland.
Wilson et al. (2001)
identified two haplotypes(1) 2.47 (haplotype #60 in our table 3
), and (2) 3.65 (haplotype #107 in our table 3
)that proved useful in inferring a Viking contribution to the Orcadian gene pool, although they noted that it might not be possible to distinguish 2.47 from an Anglo-Saxon contribution in other parts of Britain. We compared the frequencies found in the Central English, Frisian, and Norwegian samples of (1) the 2.47 and 3.65 haplotypes on their own, (2) these two haplotypes plus their one-step mutational neighbors, and (3) these two haplotypes plus their one-step networks (defined as all haplotypes within a sample connected to the named haplotype by a series of one-step mutations via observed intermediate haplotypes). As suggested by the results in the previous paragraph, in each case the frequency distribution in Central England more closely matched that in Friesland than that in Norway. Thus, neither of these two haplotypes provided any positive evidence of a (Norwegian) Viking contribution to the Central English gene pool that could not be explained by a substantial contribution originating in Friesland only.
Population Genetic Models
We explored various population genetic models (see Materials and Methods) to evaluate whether or not a large Anglo-Saxon migration event is needed to explain the extremely high Central English-Frisian affinity. We started with a simple model of population fission with no background migration. We found a 95% credible interval for the split date using BATWING of 088 generations (02,200 years BP, assuming 25 years per generation), which corresponded well with the 95% confidence interval from the Monte Carlo likelihood method with no background migration (091 generations or 02,275 years BP assuming 25 years per generation).
Next, we looked at the levels of background migration, operating continuously from generation to generation, needed to maintain the Central English-Frisian genetic similarity under two other scenarios not involving Anglo-Saxon mass migration. Under an Island Model scenario (constant background migration between two populations that split at TS = ) the 95% confidence interval for m, estimated from the Monte Carlo likelihood method, is 0.3%50% (where 50% indicates complete panmixia and is a maximum value for m). The same result (to the significant digit given) is found under a Neolithic mass migration scenario (population split 240 generations BP). We note that a figure of m = 0.3% is three times higher than the figure we estimated as representing an implausibly high value for m, well in excess of realistic values, based on migration statistics to and from the European Economic Area as a whole over the past 25 years. If we set m at the implausibly high value of 0.1%, the 95% confidence interval for a Central English-Frisian split date is 097 generations (02,425 years BP, assuming 25 years per generation). The figure of 97 generations BP represents an extreme upper limit for the migration event in this case both because it is based on such an implausibly high value for background migration and because it requires the most severe mass migration event imaginable, namely a 100% replacement of the English Y chromosome pool.
Next, we assumed that an Anglo-Saxon migration event did take place 60 generations ago (i.e., 1,500 years BP assuming 25 years per generation) and asked how big an event would be needed to explain the Central English-Frisian genetic similarity. If the Central English and Frisian populations were very different at the time of the event, a larger mass migration would be needed. We therefore started by assuming complete genetic identity of the two populations at the time of the Neolithic (i.e., a Central English-Frisian population split 240 generations BP). Assuming no background migration, the 95% confidence interval of the proportion F of the Central English population derived from an Anglo-Saxon mass migration event is 65%100%. If a background migration rate since the Neolithic of m = 0.1% is allowed, the 95% confidence interval for F widens to 50%100%. This result is unchanged if a 30-year generation time is assumed (i.e., an Anglo-Saxon migration event 50 rather than 60 generations ago).
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The best explanation for our findings is that the Anglo-Saxon cultural transition in Central England coincided with a mass immigration from the continent. Such an event would simultaneously explain both the high Central English-Frisian affinity and the low Central English-North Welsh affinity. If we use a rate of 0.1%, as observed over the past 25 years, to represent an extremely high value for continuous background migration between Central England and continental Europe, then we estimate that an Anglo-Saxon immigration event affecting 50%100% of the Central English male gene pool at that time is required. We note, however, that our data do not allow us to distinguish an event that simply added to the indigenous Central English male gene pool from one where indigenous males were displaced elsewhere or one where indigenous males were reduced in number. Furthermore, although our models assume a single instantaneous migration event, we would also expect a more gradual process lasting several generations but still resulting in the same degree of admixture (a picture which may fit the historical data better [Härke 2002]) to produce very similar genetic patterns.
We accept that our data do not prove conclusively that an Anglo-Saxon mass migration event took place. If a background migration rate of 0.3% is allowed between Central England and Friesland, then the need for a mass migration event disappears. However, we note that this is an extremely high rate even by modern standards and would have to have been maintained continuously over thousands of years. A background migration rate of 0.3% would imply that one in six of today's Central English males descend from Frisians (or a population identical to Frisians) that emigrated to England after the Anglo-Saxon period and that an equal proportion of today's Frisians descend from English in a like manner. We also note that under a unidirectional gene flow model involving immigration into Central England only, the rate of background migration would then have to double to be at least 0.6% on a continuous basis.
It is also true that a mass migration event could have occurred outside the Anglo-Saxon migration period because the 95% confidence interval for a Central English-Frisian split extends as far back as 425 b.c. (if one allows a background migration rate of 0.1% and a generation time of 25 years). Archaeology and the testimony of Caesar combine to suggest an immigration of the Belgae, a Celtic tribe from northern Gaul, into central southern England (Hampshire and West Sussex) between 100 and 80 b.c. (Hawkes 1968
; Cunliffe 1988
, pp. 147149; Cunliffe 1991
, pp. 108110). Furthermore, although Friesland lay outside the maximum extent of the Roman Empire, small numbers of Frisian mercenaries were recruited by the Romans and stationed as far north as Hadrian's Wall (Breeze and Dobson 1978
, pp. 139140; Collingwood, Wright, and Tomlin 1995
, p. 501). However, most historians would see these movements, if they would acknowledge them at all, as preludes to post-Roman Anglo-Saxon migration, and it would be odd indeed to deny the latter while at the same time assigning an extremely large mass migration status to the former.
Finally, we accept that our inferences are based on population genetic analyses that assume a particular model of microsatellite evolution under selective neutrality and growth and that departures from these assumptions may influence our results. However, we note that the accuracy of the mutation model is diminished in importance by the small number of generations that would allow new mutations to accumulate since Anglo-Saxon times and also that any selective sweeps would also have to have been very recent in order to have influenced our conclusions greatly, especially because the effects of such sweeps would partly be accommodated by our model of exponential population growth. In addition, the estimates provided by BATWING for effective population sizes at the time of the Anglo-Saxon migration event are very small (table 1
). Thus, a large amount of error caused by drift is already allowed for by our BATWING and Monte Carlo likelihood analyses. We do not presume an exact correspondence between real and effective population size dynamics or between the real population history of England, which has seen many different changes in size, and our simple model of exponential growth. However, we note that the posterior mode of the effective population growth rate per generation provided by BATWING (6.0%) almost exactly matches the real estimated population growth rate averaged over the past 1,500 years (Hatcher 1977
, pp. 13481530; Wrigley and Schofield 1989
, pp. 15411871; Härke 2002
), whereas our 95% credible interval covers both the lower average growth rates of a.d. 5001750 (approximately 3% per 25 years, albeit with large fluctuations) and the higher average growth rates of a.d. 17502000 (approximately 23% per 25 years).
Anglo-Saxon settlements and culture appeared throughout England but, importantly, did not extend into North Wales, where many of the original Celtic Britons living in England are thought to have fled (Kearney 1989
; Davies 1993, 1999
). Conflict between the Welsh and Anglo-Saxon kingdoms continued over a long period. Offa's Dyke (an earthwork barrier 240 km long) was constructed ca. a.d. 790 and provided a well-defined boundary between England and Wales. The linguistic, cultural, and political separation of the two regions lasted at least until a.d. 1282 when Edward I of England defeated the Welsh King Llywelyn II (Davies 1993
). Our results suggest that this separation has also restricted male-mediated gene flow between the two regions over the past approximately 1500 years.
Comparisons of Central English and Norwegian haplotypes reveal no evidence of distinctive common signature haplotypes indicative of Viking origin, in contrast to Orcadian-Norwegian comparisons (Wilson et al. 2001)
. However, the Vikings who may have settled in East Anglia and the Midlands are thought to have been predominantly from Denmark, rather than Norway (Richards 2000)
. Previously published data suggest that the Danish have greater Y chromosome genetic affinity with the English than with the Norwegians (Malaspina et al. 2000; Rosser et al. 2000)
. However, the Danish-German border is believed to be another source location of the Anglo-Saxons (Kearney 1989
; Davies 1999
), so any Danish Viking influence on the English gene pool may prove difficult to distinguish from Anglo-Saxon influence. Further studies within Scandinavia and elsewhere are needed to resolve this issue.
This study shows that the Welsh border was more of a genetic barrier to Anglo-Saxon Y chromosome gene flow than the North Sea. Remarkably, we find that the resultant genetic differentiation is still discernible in the present day. These results indicate that a political boundary can be more important than a geophysical one in population genetic structuring and that informative patterns of genetic differentiation can be produced by migration events occurring within historical times.
![]() |
Acknowledgements |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
![]() |
Footnotes |
---|
1 Both these authors contributed equally to this work
Keywords: Y chromosome
unique event polymorphisms
microsatellite haplotypes
British population history
genetic anthropology
population genetic models
Address for correspondence and reprints: Michael Weale, The Centre for Genetic Anthropology, Departments of Biology and Anthropology, University College London, University of London, Darwin Building, Gower Street, London WC1E 6BT, United Kingdom. m.weale{at}ucl.ac.uk
.
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Adams W. Y., 1968 Invasion, diffusion, evolution? Antiquity 42:194-215[ISI]
Adams W. Y., D. P. Van Gerven, R. S. Levy, 1978 The retreat from migrationism Annu. Rev. Anthropol 7:483-532[ISI]
Anthony D. W., 1990 Migration in archaeology: the baby and the bathwater Am. Anthropol 92:895-914[ISI]
Arnold C. J., 1984 From Roman Britain to Saxon England Croom Helm, London
Bahlo M., R. C. Griffiths, 2000 Inference from gene trees in a subdivided population Theor. Popul. Biol 57:79-95[ISI][Medline]
Beerli P., J. Felsenstein, 2001 Maximum likelihood estimation of a migration matrix and effective population sizes in n subpopulations by using a coalescent approach Proc. Natl. Acad. Sci. USA 98:4563-4568
Bianchi N. O., C. I. Catanesi, G. Bailliet, V. L. Martinez-Marignac, C. M. Bravi, L. B. Vidal-Rioja, R. Herrera, J. S. Lopez-Camelo, 1998 Characterization of ancestral and derived Y-chromosomal haplotypes of New World populations Am. J. Hum. Genet 63:1862-1871[ISI][Medline]
Bodmer W. F., 1993 The genetics of Celtic populations Proc. Br. Acad 82:37-57
Breeze D. J., B. Dobson, 1978 Hadrian's Wall, Revised edition Pelican, Harmondsworth
Burmeister S., 2000 Archaeology and migration: approaches to an archaeological proof of migration Curr. Anthropol 41:539-567[ISI]
Cartwright R. A., H. J. Hargreaves, E. Sunderland, 1977 Serum protein and isoenzyme polymorphisms from Nottingham, England Hum. Biol 49:629-640[ISI][Medline]
Casalotti R., L. Simoni, M. Belledi, G. Barbujani, 1999 Y-chromosome polymorphisms and the origins of the European gene pool Proc. R. Soc. Lond. B 266:1959-1965[ISI]
Cavalli-Sforza L. L., P. Menozzi, A. Piazza, 1994 The history and geography of human genes Princeton University Press, Princeton, NJ
Chapman J., 1997 The impact of modern invasions and migrations on archaeological explanation Pp. 1120 in J. Chapman and H. Hamerow, eds. Migrations and invasions in archaeological explanation. BAR International Series 664, Oxford, UK
Chapman J., H. Hamerow, eds 1997 Migrations and invasions in archaeological explanation BAR International Series 664, Oxford, UK
Clark G., 1966 The invasion hypothesis in British archaeology Antiquity 40:172-189[ISI]
Collingwood R. G., R. P. Wright, R. S. O. Tomlin, 1995 The Roman inscriptions of Britain, Vol. 1, 2nd edition Sutton, Stroud
Crawford S., 1997 Britons, Anglo-Saxons and the Germanic burial ritual Pp. 4572 in J. Chapman and H. Hamerow, eds. Migrations and invasions in archaeological explanation. BAR International Series 664, Oxford, UK
Cunliffe B., 1988 Greeks, Romans and Barbarians: spheres of interaction Batsford, London
. 1991 Iron Age communities in Britain 3rd edition (Archaeology of Britain series). Routledge, London
Davies J., 1993 A History of Wales Penguin Press, London
Davies N., 1999 The Isles: a history Macmillan, London
Esmonde-Cleary A. S., 1993 Approaches to the differences between Late Romano-British and Early Anglo-Saxon archaeology Anglo-Saxon Stud. Archaeol. Hist 6:57-63
Falsetti A. B., R. R. Sokol, 1993 Genetic structure of human populations in the British Isles Ann. Hum. Biol 20:215-229[ISI][Medline]
Goldstein D. B., A. Ruiz Linares, L. L. Cavalli-Sforza, M. W. Feldman, 1995 Genetic absolute dating based on microsatellites and the origin of modern humans Proc. Natl. Acad. Sci. USA 92:6723-6727[Abstract]
Hamerow H., 1997 Migration theory and the Anglo-Saxon "identity crisis." Pp. 3344 in J. Chapman and H. Hamerow, eds. Migrations and invasions in archaeological explanation. BAR International Series 664, Oxford, UK
Härke H., 1998 Anthropologists and migrations: a problem of attitude? Curr. Anthropol 39:19-45[ISI]
. 2002 Kings and warriors: population and landscape in early medieval Britain Pp. 145175 in P. Slack and R. Ward, eds. The peopling of Britain: the shaping of a human landscape. Oxford University Press, Oxford
Hatcher J., 1977 Plague, population and the English economy Palgrave Macmillan, London
Hawkes C. F. C., 1968 New thoughts on the Belgae Antiquity 42:6-16[ISI]
Hawkes J., C. Hawkes, 1942 Prehistoric Britain Penguin, Harmondsworth, United Kingdom
Helgason A., S. Sigurdardóttir, J. Nicholson, B. Sykes, E. W. Hill, D. G. Bradley, V. Bosnes, J. R. Gulcher, R. Ward, K. Stefánsson, 2000 Estimating Scandinavian and Gaelic ancestry in the male settlers of Iceland Am. J. Hum. Genet 67:697-717[ISI][Medline]
Heyer E., J. Puymirat, P. Dieltjes, E. Bakker, P. de Knijff, 1997 Estimating Y chromosome specific microsatellite mutation frequencies using deep rooting pedigrees Hum. Mol. Genet 6:799-803
Higham N., 1992 Rome, Britain and the AngloSaxons Seaby, London
Hill E. W., M. A. Jobling, D. G. Bradley, 2000 Y-chromosome variation and Irish origins Nature 404:351-352[ISI][Medline]
Hodges R., 1989 The AngloSaxon achievement: archaeology and the beginnings of English society Duckworth, London
Hunter J., I. Ralson, eds 1998 The archaeology of Britain Routledge, London
Kayser M., S. Brauer, G. Weiss, W. Schiefenhövel, P. A. Underhill, M. Stoneking, 2001 Independent histories of human Y chromosomes from Melanesia and Australia Am. J. Hum. Genet 68:173-190[ISI][Medline]
Kayser M., A. Caglià, D. Corach, et al. (30 co-authors) 1997 Evaluation of Y-chromosomal STRs: a multicenter study Int. J. Legal Med 110:125-133[ISI][Medline]
Kayser M., L. Roewer, M. Hedman, et al. (14 co-authors) 2000 Characteristics and frequency of germline mutations at microsatellite loci from the human Y chromosome, as revealed by direct observation in father/son pairs Am. J. Hum. Genet 66:1580-1588[ISI][Medline]
Kearney H., 1989 The British Isles: a history of four nations Cambridge University Press, Cambridge
Leeds E. T., 1954 The growth of Wessex Oxoniensia 19:45-60
Long C. C., C. Darke, R. Marks, 1998 Celtic ancestry, HLA phenotype and increased risk of skin cancer Br. J. Dermatol 138:627-630[ISI][Medline]
Malaspina P., F. Cruciani, P. Santolamazza, et al. (24 co-authors) 2000 Patterns of male-specific inter-population divergence in Europe, West Asia and North Africa Ann. Hum. Genet 64:395-412[ISI][Medline]
Mascie-Taylor C. G. N., G. W. Lasker, 1996 Further notes on possible changes in the geographic distribution of ABO and Rh blood groups in Great Britain Hum. Biol 68:473-478[ISI][Medline]
Mastana S. S., R. Jayasekara, P. Fisher, R. J. Sokol, S. S. Papiha, 1993 Genetic polymorphism of orosomucoid (ORM) in populations of the United Kingdom, Indian subcontinent, and Cambodia Jpn. J. Hum. Genet 38:289-296[Medline]
Mastana S. S., R. J. Sokol, 1998 Genetic variation in the East Midlands Ann. Hum. Biol 25:43-68[ISI][Medline]
Merryweather-Clarke A. T., J. J. Pointon, J. D. Shearman, K. J. H. Robson, 1997 Global prevalence of putative haemochromatosis mutations J. Med. Genet 34:275-278[Abstract]
Michalakis Y., L. Excoffier, 1996 A generic estimation of population subdivision using distances between alleles with special reference for microsatellite loci Genetics 142:1061-1064
Myres J. N. L., 1986 The English settlements Oxford University Press, Oxford
Näsman U., 1988 Den folkvandringstiden krisen i Sydskandinavien, inklusive Öland och Gotland Pp. 227255 in U. Näsman and J. Lund, eds. Folkevandringstiden i Norden: En krisetid mellem ldre og yngre jernalder. Aarhus Universitetsforlag, Aarhus
Nei M., 1987 Molecular evolutionary genetics Columbia University Press, New York
Nielsen H. F., 1985 Old English and the continental Germanic languages: a survey of morphological and phonological interrelations 2nd edition. Institut für Sprachwissenschaft der Universität Innsbruck, Innsbruck
Nielsen R., J. Wakeley, 2001 Distinguishing migration from isolation: a Markov chain Monte Carlo approach Genetics 158:885-896
Papiha S. S., M. F. Duggan Keen, R. S. E. Rodger, 1985 DR antigens and Bf allotypes in northeast England, UK Hum. Hered 35:246-250[ISI][Medline]
Petersen P. V., 1991 Nye fund af metalsager fra yngre germansk jernalder: Detektorfund og danefæ fra perioden 196688 Pp. 4965 in P. Mortensen and B. M. Rasmussen, eds. Fra Stamme til Stat i Danmark 2: Høvdingesamfund og Kongemagt. Aarhus Universitetsforlag, Aarhus
Pooley C., J. Turnbull, 1998 Migration and mobility in Britain since the eighteenth century UCL Press, London
Poser C. M., 1994 The dissemination of multiple-sclerosisa viking sagaa historical essay Ann. Neurol 36:S231-S243[ISI][Medline]
Raymond M., F. Rousset, 1995 An exact test for population differentiation Evolution 49:1280-1283[ISI]
Renfrew C., 1987 Archaeology and language: the puzzle of IndoEuropean origins Jonathan Cape, London
Reynolds J., B. S. Weir, C. C. Cockerham, 1983 Estimation of the coancestry coefficient: basis for a short-term genetic distance Genetics 105:767-779
Richards J. D., 2000 Viking age England Stroud, Tempus
Richards M., V. Macaulay, E. Hickey, et al. (37 co-authors) 2000 Tracing European founder lineages in the Near Eastern mtDNA pool Am. J. Hum. Genet 67:1251-1276[ISI][Medline]
Rosser Z. H., T. Zerjal, M. E. Hurles, et al. (63 co-authors) 2000 Y-chromosomal diversity in Europe is clinal and influenced primarily by geography, rather than by language Am. J. Hum. Genet 67:1526-1543[ISI][Medline]
Semino O., G. Passarino, P. J. Oefner, et al. (17 co-authors) 2000 The genetic legacy of Paleolithic Homo sapiens sapiens in extant Europeans: a Y chromosome perspective Science 290:1155-1159
Simoni L., F. Calafell, D. Pettener, J. Bertranpetit, G. Barbujani, 2000 Geographic patterns of mtDNA diversity in Europe Am. J. Hum. Genet 66:262-278[ISI][Medline]
Shennan S., 2000 Population, culture, history, and the dynamics of culture change Curr. Anthropol 41:811-835[ISI]
Thomas M. G., N. Bradman, H. M. Flinn, 1999 High throughput analysis of 10 microsatellite and 11 binary polymorphisms on the human Y-chromosome Hum. Genet 105:577-581[ISI][Medline]
Thomas M. G., K. Skorecki, H. Ben-Ami, T. Parfitt, N. Bradman, D. B. Goldstein, 1998 Origins of Old Testament priests Nature 394:138-140[ISI][Medline]
Torroni A., H. Bandelt, H. D'Urbano, et al. (11 co-authors) 1998 mtDNA analysis reveals a major Late Paleolithic population expansion from southwestern to northeastern Europe Am. J. Hum. Genet 62:1137-1152[ISI][Medline]
Tyfield L. A., M. J. Osborn, J. B. Holton, 1997 Sequence variation at the phenylalanine hydroxylase gene in the British Isles Am. J. Hum. Genet 60:388-396[ISI][Medline]
Underhill P. A., P. Shen, A. A. Lin, et al. (21 co-authors) 2000 Y chromosome sequence variation and the history of human populations Nat. Genet 26:358-361[ISI][Medline]
Weale M. E., L. Yepiskoposyan, R. F. Jager, N. Hovhannisyan, A. Khudoyan, O. Burbage-Hall, N. Bradman, M. G. Thomas, 2001 Armenian Y chromosome haplotypes reveal strong regional structure within a single ethno-national group Hum. Genet 109:659-674[ISI][Medline]
Wilson I. J., D. J. Balding, 1998 Genealogical inference from microsatellite data Genetics 150:499-510
Wilson J. F., D. A. Weiss, M. Richards, M. G. Thomas, N. Bradman, D. B. Goldstein, 2001 Genetic evidence for different male and female roles during cultural transitions in the British Isles Proc. Natl. Acad. Sci. USA 98:5078-5083
Wrigley E. A., R. S. Schofield, 1989 The population history of England Cambridge University Press, Cambridge
The Y Chromosome Consortium. 2002 A nomenclature system for the tree of human Y-chromosomal binary haplogroups Genome Res 12:339-348