December 04, 2011

Old and recent clines in Brabant

This paper uses genealogical data to show that while some clines observed today stretch back to pre-industrial times, others do not. This is a nice result that shows that:
  • It's best to try to find test subjects with deep genealogies when one makes inferences about the past
  • Clines in modern-day populations may reflect very recent events, and not necessarily deep historical or even archaeological events
It should be mentioned that the paper does not contradict broad trends within the mentioned haplogroups that have been previously described. And, of course, this makes sense, since broad trends are more difficult to establish than those at the small-scale geographical level.

There is evidence for discontinuity at the European level across thousands of years, and it seems that we won't be able to escape the inevitable chore of figuring out "who went were" across all time scales, rather than relying on simplistic models of Paleolithic hunters receiving Neolithic farmers, and the two living happily ever after around the same hearths until today.

European Journal of Human Genetics , (30 November 2011) | doi:10.1038/ejhg.2011.218

Temporal differentiation across a West-European Y-chromosomal cline: genealogy as a tool in human population genetics

Maarten HD Larmuseau et al.

The pattern of population genetic variation and allele frequencies within a species are unstable and are changing over time according to different evolutionary factors. For humans, it is possible to combine detailed patrilineal genealogical records with deep Y-chromosome (Y-chr) genotyping to disentangle signals of historical population genetic structures because of the exponential increase in genetic genealogical data. To test this approach, we studied the temporal pattern of the ‘autochthonous’ micro-geographical genetic structure in the region of Brabant in Belgium and the Netherlands (Northwest Europe). Genealogical data of 881 individuals from Northwest Europe were collected, from which 634 family trees showed a residence within Brabant for at least one generation. The Y-chr genetic variation of the 634 participants was investigated using 110 Y-SNPs and 38 Y-STRs and linked to particular locations within Brabant on specific time periods based on genealogical records. Significant temporal variation in the Y-chr distribution was detected through a north–south gradient in the frequencies distribution of sub-haplogroup R1b1b2a1 (R-U106), next to an opposite trend for R1b1b2a2g (R-U152). The gradient on R-U106 faded in time and even became totally invisible during the Industrial Revolution in the first half of the nineteenth century. Therefore, genealogical data for at least 200 years are required to study small-scale ‘autochthonous’ population structure in Western Europe.


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