Over a year ago, there appeared one of the few studies of autosomal DNA in Ireland and Britain. If you have English/Welsh, Irish, northern Irish, Highlands Scottish, Lowlands Scottish or Swedish matches, you will want to read this post. Here is the original article and abstract.
Population structure and genome-wide patterns of variation in Ireland and Britain.
Located off the northwestern coast of the European mainland, Britain and Ireland were among the last regions of Europe to be colonized by modern humans after the last glacial maximum. Further, the geographical location of Britain, and in particular of Ireland, is such that the impact of historical migration has been minimal. Genetic diversity studies applying the Y chromosome and mitochondrial systems have indicated reduced diversity and an increased population structure across Britain and Ireland relative to the European mainland. Such characteristics would have implications for genetic mapping studies of complex disease. We set out to further our understanding of the genetic architecture of the region from the perspective of (i) population structure, (ii) linkage disequilibrium (LD), (iii) homozygosity and (iv) haplotype diversity (HD). Analysis was conducted on 3654 individuals from Ireland, Britain (with regional sampling in Scotland), Bulgaria, Portugal, Sweden and the Utah HapMap collection. Our results indicate a subtle but clear genetic structure across Britain and Ireland, although levels of structure were reduced in comparison with average cross-European structure. We observed slightly elevated levels of LD and homozygosity in the Irish population compared with neighbouring European populations. We also report on a cline of HD across Europe with greatest levels in southern populations and lowest levels in Ireland and Scotland. These results are consistent with our understanding of the population history of Europe and promote Ireland and Scotland as relatively homogenous resources for genetic mapping of rare variants.
Though the focus was on genome-wide association studies (GWAS) and linkage disequilibrium, or medical aspects of DNA, this study was groundbreaking in using supercomputing and has enormous implications for the history of the British Isles. It used data from over 3,000 individuals from seven populations:
6. South/Southeast England
Data came from several sources: the International Schizophrenia Consortium, Wellcome Trust Cast Control Consortium 1958 Birth Control Data set, Utah European ancestry population (CEU) and HapMap project.
The study aimed to describe, statistically, four measures of the Irish and English populations:
1. Population structure
2. Linkage disequilibrium, with consequences for the study of common Irish and English genetic disorders
3. ROH, or runs of homozygosity, essentially a reflection of inbreeding and the remoteness of a population
4. Haplotype diversity (based on SNPs in atDNA)
The main conclusion was that Irish/English formed a separate and unique population since the Ice Age very different from either Bulgarian (SE Europe) or Portuguese (SW Europe), with great affinities to Sweden or Scandinavian populations (p. 1250). For instance, "the breakdown and patterning of LD [linkage disequilibrium] ... is virtually indistinguishable among the Irish, Scottish, southern English, Swedish..." (p. 1250).
"Diversity across Britain and Ireland is reduced in comparison with mainland European populations, with Scotland and Ireland having lower levels than southern England (p. 1251)."
The study postulates that Irish and English proneness to genetic disease came about as a result of population stasis or unchanging conditions. The agricultural revolution swept in a lot of additions to the gene pool in most of Europe, including Southeast England, but in areas like Ireland, Scotland and Sweden the same population stayed on the land with little increase, in fact with a negative effect during the Norse migrations of the 10th century and the Irish Potato Famine. The study mentions a "kinship effect" apparent in Irish and Scottish clan histories (p. 1254).
The surprising suggestion is that there will now be a groundswell of research into "Irish" and "Scottish" and "English" diseases comparable to Jewish diseases.
A related study is:
A. Auton, K. Bryc, A. Boyko, K. Lohmueller, J. Novembre, A. Reynolds, A.
Indap, M. H. Wright, J. Degenhardt, R. Gutenkunst, K. S. King, M. R.
Nelson and C. D. Bustamante, Global distribution of genomic diversity
underscores rich complex history of continental human populations,
Genome Research, February 2009. Abstract.