10.4 Evidence of introgression

Discordant trees can also be produced by introgression. In this case, the B allele arises on the Neanderthal lineage and is passed from Neanderthals into a human population, creating either an ABBA or BABA pattern (depending on which population receives Neanderthal gene flow).

Fig. 4. ABBA and BABA allele patterns formed by Neanderthal introgression.
Fig. 4. ABBA and BABA allele patterns formed by Neanderthal introgression.
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