Tuesday, December 02, 2008

More on Y-chromosome DNA testing

In the previous post, I reviewed Stephen Oppenheimer's theory of the genetic makeup of the British Isles. He concluded that most British and Irish people can trace their male descent to aboriginal Europeans who recolonised the British Isles after the last age-age, more than 8,000 years ago. They came from the warm 'basque refuge' in northern Spain and southern France.

The Y-chromosome type of this lineage is technically R1b, called 'Oisin' by Bryan Syke's company Oxford Ancestors, and 'Ruisko' by Stephen Oppenheimer's company Ethnoancestry (all of which will sell you a DNA test!).

However, as water levels rose in the Mesolithic, some of the R1b descendant population moved up the channel and then the Seine or the Rhine to colonise Northern France, Germany and Denmark. Previously, other R1b descendants had progressed round the north of Scotland to Norway and spread into Scandinavia.

There the basal R1b-type Y-chromosome accumulated further mutations, and its bearers became Vikings, Jutes, Angles and Saxons - and Celts. Some of them diffused back into England from the east, as discussed in the previous post.

It follows that possession of the R1b male Y-chromosome type cannot indicate whether one's more immediate ancestors were Britain's former 'Celtic-speaking' inhabitants, or whether they were part of the Saxon, Anglic, Jutish or Norse population who carried the R1b gene cluster. To achieve a further level of discrimination one must look at the details of the Y-chromosome.

In DNA analysis, certain marker points are located on the Y chromosome where a sequence of nucleotides (G, A, C, T) repeats. The number of such repetitions is the mutation variable. The sites are labelled with a code such as "DYS 19" where DYS stands for DNA Y-chromosome Segment (see the Wikipedia description here). So DYS 19 = 14 means 14 repetitions at this marker site.

By looking at the exact number of repetitions at each marker point, the more recent paternal ancestry can be narrowed down to a much more specific region, based on databases of samples from today's population, carefully chosen to have had ancestors living in the same small area for as long as possible. Up to a few hundred years ago populations were pretty geographically localised.

Much of this information is proprietary, and is used to drive the business models of DNA-testing companies, but there is some on the web, and you can google for matches. For example, try googling R1b DYS 390 23 and you will see sites suggesting that this R1b variant is Germanic! Another interesting site is here.

To help in the process, here is my Y-chromosome data (from Oxford Ancestors).

DYS 19 = 14 repetitions
DYS 388 = 11
DYS 390 = 23
DYS 391 = 11
DYS 392 = 13
DYS 393 = 13
DYS 389i = 10
DYS 389ii-i = 16
DYS 425 = 12
DYS 426 = 12

This is the Atlantic Modal Haplotype, described here.

In case this seems awfully male chauvinist, it should be pointed out that the Y-chromosome shows considerably greater variation than mitochondrial DNA, and this greater mutation rate is what allows recent variations of geography to be determined.

I have no plans to spend any more money on further refining my more recent paternal ancestry - it seems more likely to be German/Danish than 'Celtic'. Perhaps it will all end up being free on the web for future Google searches: you can already get a long way.

Previous: The Origins of the British