Crossbreeding, not just cultural influences, led hunter-gatherers to adopt livestock practices
By Bruce Bower
Ancient sheep, goat and cattle herders made Africa their home by hooking up with the continent’s native hunter-gatherers, a study suggests.
DNA analysis shows that African herders and foragers mated with each other in two phases, says a team led by archaeologist Mary Prendergast of Saint Louis University in Madrid. After entering northeastern Africa from the Middle East around 8,000 years ago, herders swapped DNA with native foragers between roughly 6,000 and 5,000 years ago. Herders possessing some forager heritage then trekked about halfway down the continent and mated with eastern African foragers around 4,000 years ago, the scientists report online May 30 in Science.
Present-day herders, such as the Dinka in South Sudan, still live in eastern Africa. But how pastoralism spread into the region has been a mystery. In particular, it has been difficult to tell whether ancient African hunter-gatherers mated with early herders or simply adopted their livestock practices. The new study supports an emerging view from ancient DNA studies that human cultural evolution has often featured mating across groups with different traditions and lifestyles.
Prendergast and her colleagues analyzed tooth and bone DNA from 41 individuals whose remains were previously found at herding and foraging sites in Kenya and Tanzania with ages ranging between about 4,000 and 100 years old. Those genetic data were compared with DNA previously collected by other researchers from present-day African herders as well as DNA extracted from roughly 6,000-year-old remains of Middle Eastern farmers — the closest population to northeastern Africa at that time with available genetic data — and bones of African foragers, including one who lived in East Africa as early as 4,500 years ago (SN: 11/14/15, p. 12).
Early African herders inherited about 20 percent of their DNA from foragers, mostly via mating that occurred before 5,000 years ago, the scientists say. Herders then spread rapidly throughout eastern Africa after 3,300 years ago, mating little with foragers along the way.
M.E. Prendergast et al. Ancient DNA reveals a multistep spread of the first herders into sub-Saharan Africa. Science. Published online May 30, 2019. doi:10.1126/science.aaw6275. Further Reading
B. Bower. Into Africa: ancient skeleton sheds light on reverse migration. Science News. Vol. 188, November 14, 2015, p. 12.
B. Bower. Ancient North Africans got milk. Science News Online, June 20, 2012.