Sequencing and analysis of ancient African genomes suggests that humans first began to diverge as a population between 350,000 and 260,000 years ago. Anatomically modern humans evolved in Africa, but placing that date has been difficult based on analyses of modern population genomes. Here, Carina M. Schlebusch and colleagues report the genomes of seven ancient individuals from what is modern-day South Africa. Three were hunter-gatherers who lived during the Stone Age, roughly 2,000 years ago, and four were farmers during the Iron Age, living between 500 and 300 years ago. The team analyzed these seven genomes along with databases of modern and archaic genomes from around the world. They focused on the relatively high-quality genetic information derived from a hunter-gatherer boy who lived in the Stone Age and was unaffected by genetic admixture with humans in other areas of Africa and Eurasia. They used a technique to systematically compare his genome to other groups without biases that arise in analyzing ancient DNA. Comparison of the ancient genome and numerous others across various regions and time consistently suggested that human populations diverged between 350,000 and 260,000 years ago, which the authors note is consistent with the fossil records. This is roughly half the time spanning the split of humans from Neandertals and Denisovans. Also of interest, the authors found that three of the Iron Age individuals carried a gene variant that protected against malaria and two had a variant that is associated with resistance to sleeping sickness, whereas the older individuals from the Stone Age did not have these protective variants.
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Journal
Science