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Saturday, August 31, 2013

PCA of the world


Following on from my last blog entry, in which I posted a PCA of West Eurasia, below is a PCA of the world. The outcome obviously looks very different, and that's because here the positions of the samples are determined by genetic clines that dominate the globe, and these are different from those that dominate West Eurasia. To view a much larger and detailed version of the image below, click on it. Individual IDs are shown in the PDF here.




See also...

A multidimensional view of Europe + West Asia

A multidimensional view of East Asia


Tuesday, August 20, 2013

Principal component analysis (PCA) of West Eurasia


In the past I've done MDS and SPA analyses of West Eurasia, but below is a PCA. Anorther version with individual IDs is available here.

The first eigenvector is a reflection of the genetic cline that runs from Northern Europe to the Middle East, with Finns being the most Northern European and Saudis and some Bedouin the most Middle Eastern. Mediterranean ancestry defines the second eigenvector, with Sardinians being the most Mediterranean, and the Mari of the Volga-Ural region the least.



See also...

Cluster analysis of West Eurasia: 13 clusters from 18 dimensions

PCA of the world

A multidimensional view of Europe + West Asia


Thursday, August 8, 2013

Moorjani et al. on recent population mixture in India


Despite some claims to the contrary across the web today, there's really nothing new or controversial about this Moorjani et al. paper, considering all of the non-academic data available online on South Asian genome-wide and Y-chromosome genetic structure. In fact, I think the authors were way too cautious and diplomatic in their assessment of the post-Neolithic population history of the region.

It is also important to emphasize what our study has not shown. Although we have documented evidence for mixture in India between about 1,900 and 4,200 years BP, this does not imply migration from West Eurasia into India during this time. On the contrary, a recent study that searched for West Eurasian groups most closely related to the ANI ancestors of Indians failed to find any evidence for shared ancestry between the ANI and groups in West Eurasia within the past 12,500 years3 (although it is possible that with further sampling and new methods such relatedness might be detected). An alternative possibility that is also consistent with our data is that the ANI and ASI were both living in or near South Asia for a substantial period prior to their mixture. Such a pattern has been documented elsewhere; for example, ancient DNA studies of northern Europeans have shown that Neolithic farmers originating in Western Asia migrated to Europe about 7,500 years BP but did not mix with local hunter gatherers until thousands of years later to form the present-day populations of northern Europe.15, 16, 44 and 45

Here's my non-diplomatic assessment of the data presented in the paper: South Asia has seen multiple waves of population movements from West and Central Asia since the Neolithic, including the Indo-Aryan invasion during the Bronze Age, which reshaped the genetic structure of the region in a remarkable way. Indeed, the Aryan invasion introduced into South Asia one of the most common Y-chromosome lineages there today: R1a-Z93 or R1a1a1b2*. Obviously, scientists working on the problem of the peopling of South Asia really need to become aware of this marker, and in particular its very close relationship to the Northern and Eastern European-specific R1a-Z283.

Citation...

Priya Moorjani et al., Genetic Evidence for Recent Population Mixture in India, The American Journal of Human Genetics, 08 August 2013, doi:10.1016/j.ajhg.2013.07.006

See also...

Origins of R1a1a in or near Europe (aka. R1a1a out of India theory looks like a dud)

South Asian R1a in the 1000 Genomes Project

Southwest Eurasians + Northwest Eurasians + Mesolithic survivors = modern Europeans