Wednesday, April 04, 2018

Confused: The Genomic Formation of South and Central Asia

The recent preprint under discussion: The Genomic Formation of South and Central Asia, has the passages below.

Suppose you said that X and Y had a similar ancestry profile of a Norwegian and Italian mix, except that Y also had 22% Japanese ancestry.  It makes one wonder, what does a "similar ancestry profile" mean? 

276 Third, between 3100-2200 BCE we observe an outlier at the BMAC site of Gonur, as well as two
277 outliers from the eastern Iranian site of Shahr-i-Sokhta, all with an ancestry profile similar to 41
278 ancient individuals from northern Pakistan who lived approximately a millennium later in the
279 isolated Swat region of the northern Indus Valley (1200-800 BCE). These individuals had
280 between 14-42% of their ancestry related to the AASI and the rest related to early Iranian
281 agriculturalists and West_Siberian_HG. Like contemporary and earlier samples from Iran/Turan
282 we find no evidence of Steppe-pastoralist-related ancestry in these samples. In contrast to all
283 other Iran/Turan samples, we find that these individuals also had negligible Anatolian
284 agriculturalist-related admixture, suggesting that they might be migrants from a population
285 further east along the cline of decreasing Anatolian agriculturalist ancestry. While we do not
286 have access to any DNA directly sampled from the Indus Valley Civilization (IVC), based on (a)
287 archaeological evidence of material culture exchange between the IVC and both BMAC to its
288 north and Shahr-i-Sokhta to its east (27), (b) the similarity of these outlier individuals to post-
289 IVC Swat Valley individuals described in the next section (27), (c) the presence of substantial
290 AASI admixture in these samples suggesting that they are migrants from South Asia, and (d) the
291 fact that these individuals fit as ancestral populations for present-day Indian groups in qpAdm
292 modeling, we hypothesize that these outliers were recent migrants from the IVC.

449 Finally, we examined our Swat Valley time transect from 1200 BCE to 1 CE. While the earliest
450 group of samples (SPGT) is genetically very similar to the Indus_Periphery samples from the
451 sites of Gonur and Shahr-i-Sokhta, they also differ significantly in harboring Steppe_MLBA
452 ancestry (~22%). This provides direct evidence for Steppe_MLBA ancestry being integrated into
453 South Asian groups in the 2nd millennium BCE, and is also consistent with the evidence of
454 southward expansions of Steppe_MLBA groups through Turan at this time via outliers from the
455 main BMAC cluster from 2000-1500 BCE. Later samples from the Swat time transect from the
456 1st millennium BCE had higher proportions of Steppe and AASI derived ancestry more similar to
457 that found on the Indian Cline, showing that there was an increasing percolation of Steppe
458 derived ancestry into the region and additional admixture with the ASI through time.


tim drake said...

Suppose you said that X and Y had a similar ancestry profile of a Norwegian and Italian mix, except that Y also had 22% Japanese ancestry. It makes one wonder, what does a "similar ancestry profile" mean ---- the percentages vary .
I think it's like X had 50 % Norwegian and 50% Italian. Y has 39% Norwegian,39% Italian and 22 % Japanese. Please check the admixture graph.

tim drake said...!/vizhome/TheGenomicFormationofSouthandCentralAsia/Fig_1

Arun said...

Then it is not a similar ancestry profile.
Would you say all Indians have a similar ancestry profile?
They, after all, are made of varying proportions of ANI and ASI.