Sunday, February 9, 2014

North-South Ancient Admixture in Central-South Eurasia, Revisited

 
Quite early in the history of this blog, on November 3rd, 2010, I wrote a post discussing a minor "signal" I had noticed buried in the Dodecad admixture results for populations of Eastern Europe, the Middle East and South Asia.  The "signal" consisted of a combination of two Admixture components: "Northeast Asian" and "East Asian".  You can read about that early post here.  I've added a few thoughts on this topic recently, noting that the pattern is likely evidence of ancient bidirectional gene flow. (See Max Born on receiving the 1954 Nobel Prize . . ., Update, February 1, 2014.) 
 
In this post, I look at additional major components such as the "West Asian" component.
 
Reviewing observations from the previous posts, a number of deductions are possible:
 
1.  The "Northeast Asian"-"East Asian" admixture components are geographically correlated.
 
2.  The pattern extends from the Volga region of Southern Russia (Chuvash), into the Caucasus and Black Sea,  then into Pakistan, splitting westward through Syria into the Fertile Crescent, touching even into Egypt, and separately, trailing south through Pakistan extending west along the South Asian coast.
 
3.  The pattern is widely diffused compared to other admixture components.  In particular, it is much more widely diffused compared to the "North European" component and the "West Asian" component.  This wide diffusion is possibly indicative of great age since coalescence.
 
4.  As argued in the February 1st update of the post Max Born on receiving the 1954 Nobel Prize . . ., the "North European" component is likely correlated with pre-Ice Age hunter gatherers. 
 
5.  The "North European" component does not appear to be correlated with the "Northeast Asian"-"East Asian" pattern and is likely a superposition on it.
 
6.  The "Northeast Asian"-"East Asian" component does not appear to be present in the following populations considered in the Dodecad Admixture run:  Lithuanians, Cypriots, Spanish, French Basques, Tuscans, French, Northern Italians, Armenians, and Mozabite Berbers.  It is therefore uncorrelated with admixture in these populations.
 
In this post today, I look at three other major Admixture components with respect to the "Northeast Asian"-"East Asian" pattern.  These are the "West Asian", the "Southwest Asian" and the "Southern European" components.

Again, the data is normalized on the "Northeast Asian"-"East Asian" pattern. The remaining un-normalized components are allowed to float above this.  Figure 1 shows the zoomed in view with the normalization pattern running along the bottom.  This normalization approach corresponds with a North-South geographic pattern, as described in item "2." above.  Figure 2 shows the same data, but from a "zoomed out" perspective.  Populations are listed below Figure 2.

Figure 1:  Admixture components with normalized "Northeast Asian"-"East Asian" pattern show at bottom.  Components are arranged with highest "Northeast Asian" contribution on the left and highest "East Asian" contribution on the right.
 
Figure 2:  As in Figure 1, but "zoomed out" to fully show the un-normalized major components floating above the normalized "Northeast Asian"-"East Asian" pattern.
 
 Populations:
    1:  Chuvash
    2:  Lezgin
    3:  Georgian
    4:  Sindhi
    5:  Belorussian
    6:  Adygei
    7.  Pathan
    8:  Syrian
    9:  Turk
   10: Jordanian
   11: Romanian
   12: Ashkenazi
   13: North Kannadi
   14: Gujarati
   15: Uygur
   16: Burusho
   17: Egyptian

Looking at the above plots, the essential question to be asked is this:  Is there a correlation between the "Northeast Asian"-"East Asian" pattern and
 
1.  the "West Asian" component,
2.  the "Southwest Asian" component, or
3.  the "Southern European" component
 
?
 
The "West Asian" component is widely distributed.  In a few noticeable cases, such as the Chuvash, the Uygurs, the Burusho, and the North Kannadi, the "West Asian" component is only a very low level admixture component.  Based on this, it cannot be argued that the "West Asian" component is strongly correlated across the ancient "Northeast Asian"-"East Asian" pattern.  Moreover, the "West Asian" component is likely a superposition on this pre-existing population.  On the other hand, it has already been argued in another post that the point of coalescence of the "West Asian" component is somewhere in the Caucasus.   The distribution of the "West Asian" component centered about Georgians is vaguely apparent here.
 
The distributions of the other two major components "Southwest Asian" and "Southern European" are sparse and loosely distributed.   There does not appear to be an easily observable correlation between the ancient "Northeast Asian"-"East Asian" pattern and these components, at least from this data.


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