I work in the genetics dept at my uni.
This story last week created a mini uproar.
The Mandenka and Biaka had the highest rate of mixture, the San the lowest according to 2 grad students I talked with and a professor.
The Yoruba probably are similar to the Mandenka and Biaka but have yet to be tested although there are studies ongoing.
Another problem is the base use of African DNA to test White/Asian DNA against in the study last year that indicated Neanderthal mixture in Whites/Asians. If the African DNA is admixed, then the Neanderthal admixture in White/Asian populations could be even higher.
Still its impossible to determine because there is no base human DNA sequence unless we use fossil DNA.
Thats why this case is so interesting. Blacks of West African descent were the only ones with this admixture, and also interestingly blacks of West African descent dominate the sprints. The causation is very clear, and its something I would like to study.