Excavating past population structures by surname-based sampling: the genetic legacy of the Vikings in northwest England

Abstract

The genetic structures of past human populations are obscured by recent migrations and expansions and have been observed only indirectly by inference from modern samples. However, the unique link between a heritable cultural marker, the patrilineal surname, and a genetic marker, the Y chromosome, provides a means to target sets of modern individuals that might resemble populations at the time of surname establishment. As a test case, we studied samples from the Wirral Peninsula and West Lancashire, in northwest England. Place-names and archaeology show clear evidence of a past Viking presence, but heavy immigration and population growth since the industrial revolution are likely to have weakened the genetic signal of a 1,000-year-old Scandinavian contribution. Samples ascertained on the basis of 2 generations of residence were compared with independent samples based on known ancestry in the region plus the possession of a surname known from historical records to have been present there in medieval times. The Y-chromosomal haplotypes of these 2 sets of samples are significantly different, and in admixture analyses, the surname-ascertained samples show markedly greater Scandinavian ancestry proportions, supporting the idea that northwest England was once heavily populated by Scandinavian settlers. The method of historical surname-based ascertainment promises to allow investigation of the influence of migration and drift over the last few centuries in changing the population structure of Britain and will have general utility in other regions where surnames are patrilineal and suitable historical records survive.

Figure 1. Location of the Wirral peninsula and West Lancashire

Sampling ocations for the ‘modern’ samples are shown by filled circles, and unfilled circles show major towns for orientation. Gray triangles show the locations of Scandinavian major place-names (Harding 2002).

Figure 2. Y-chromosomal haplogroups in Wirral and West Lancashire samples, and controls

Binary marker phylogeny of the Y chromosome, showing mutations on the branches of the tree, and shorthand haplogroup names (Jobling and Tyler-Smith 2003) beneath. Mutations in bold italic type were also typed in the study of Capelli et al. (Capelli et al. 2003). Below the phylogeny are given the number of chromosomes carrying the haplogroup, with percentages in parentheses. n: sample size. h: Nei's unbiased estimator of gene diversity. With the exception of Mid-Cheshire, data on the control populations are from Capelli et al. (Capelli et al. 2003), and in these samples haplogroups G and H are subsumed under F*, since the markers M69 and M201 were not typed. Lancs: Lancashire.

Figure 3. Haplogroup distributions in Wirral, West Lancashire and control populations

a) Haplogroup profiles of ‘modern’ samples from the Wirral and West Lancashire, and from control populations. Sectors in pie charts are colored according to haplogroup, and sector areas are proportional to haplogroup frequency. Lancs: Lancashire. b) Haplogroup profiles of ‘medieval’ samples from the Wirral and West Lancashire, ascertained by surname.

Figure 4. Multidimensional scaling (MDS) plots illustrating the relationships between Wirral, West Lancashire and control populations

a) MDS based on population pairwise F_ST values from haplogroup data. Dotted arrows highlight the differences between ‘modern’ and ‘medieval’ Wirral and West Lancashire samples. Lancs: Lancashire. b) MDS based on population pairwise R_ST values from microsatellite data.