Yet question marks have always remained as to the exact migratory route taken by these peoples: while a first theory known as "early split" claimed that the Bantu populations immediately divided into two groups on leaving their homeland, one heading east and one south, the "late split" theory suggests that Bantu speakers actually began by traversing the equatorial forest (today part of Gabon), before dividing into two migration waves, one continuing south and the other to East Africa.
The scientists then explored the admixture of Bantu speakers with the local populations they came into contact with. Their research demonstrates that over the past millennium, the Bantus admixed with pygmy populations from West-Central Africa, Afro-Asiatic-speaking populations from East Africa and San populations from South Africa. Surprisingly, these successive admixture events appear to have been beneficial for the Bantu peoples, conferring advantageous genetic mutations that helped them adapt to their new environments. From the admixture with pygmies, for example, Bantu peoples acquired a new form of the HLA system, which helps trigger immune response to infection. Another compelling example indicates that when the Bantus arrived in eastern Sub-Saharan Africa, the local populations passed on a variability associated with the gene that codes for lactase, which enables individuals to continue digesting milk in adulthood. 2b1af7f3a8