It is known that animal herding, which had been in northeastern Africa since about 8,000 years ago, made it to southern Africa by about 2,000 years ago. But it has been an open question whether the pastoral life was brought south by immigrants, or whether it was adopted by hunter-gatherers already in the area.
A multinational team of scientists recently examined 41 genomes from individuals who lived in Africa between 4,000 and 300 years ago. The genomes suggested that pastoralists migrated from southwestern Asia into eastern Africa around 5,000 years ago. They interbred with local foragers, mixing genomes.
However, about 3,300 years ago, the inbreeding ceased. Pastoralism had already been established by this point. The immigrants were now locals. So this study creates a new question: why did the genomes separate? What happened that pastoralists and hunter-gatherers suddenly stop intermarrying?