torstai 26. helmikuuta 2015

Admixture test: Lithuanian mystery or unreliability of results

I made recently some f4-statistics in purpose to find out the Scandinavian admixture among East Europeans and Finns.  My formula was

f4(test,West-Finland;Norwegian,Mbuti)

The result made me wondering how much the genetic structure of sample groups has effect on the result:

Lithuania West-Finland  :     Norway      MBUTI      0.0027     2.905
Poland West-Finland  :     Norway      MBUTI     -0.0004    -0.583
Belarussia West-Finland  :     Norway      MBUTI     -0.0013    -1.620
RU_Smolensk West-Finland  :     Norway      MBUTI     -0.0002    -0.155
RU_west West-Finland  :     Norway      MBUTI     -0.0030    -3.779
RU_Tver West-Finland  :     Norway      MBUTI     -0.0031    -2.589
RU-Kostr West-Finland  :     Norway      MBUTI     -0.0054    -5.131
Romania West-Finland  :     Norway      MBUTI     -0.0105   -10.318
Bulgaria West-Finland  :     Norway      MBUTI     -0.0094   -10.234
Ukraine West-Finland  :     Norway      MBUTI     -0.0033    -4.404
Chuvash West-Finland  :     Norway      MBUTI     -0.0231   -24.172

Chuvashes are for a control purpose.


The result shows that the Lithuanians show more common admixture with Norwegians than the Finns do and they are the only group exceeding Western Finnish - Norwegian admixture.
 
Lithuanians share also more admixture with Chuvashes than Mordvas and North-Russians do.  They show more admixture than their neighbours, as well in east as in west. 

Mordva  Lithuania  :    Chuvash      MBUTI     -0.0039    -4.050
RU_Vologda  Lithuania  :    Chuvash      MBUTI     -0.0033    -3.406

Then I replaced the data base to the one published by Lazaridis et al. 2014, to confirm this observation.  I also changed the outgroup to Chimp.  There are some differences in sample groups, so also some differences are expected, but this result confirms what I got in the first test.

                                                             D stat         Z
Lithuanian     West-Finnish :  Norwegian      Chimp      0.0032     2.818
Belarusian      West-Finnish :  Norwegian      Chimp     -0.0026    -2.291
Bulgarian        West-Finnish :  Norwegian      Chimp     -0.0091    -7.949
Chuvash        West-Finnish  :  Norwegian      Chimp     -0.0248   -20.419



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