Modern humans may have emerged 350,000 years ago – much earlier than thought, say scientists who have analysed the genome of seven individuals who lived in southern Africa between 2,300 and 300 years ago.
Analysis of ancient human remains from KwaZulu-Natal revealed that southern Africa has an important role to play in writing the history of humankind.
The three oldest individuals dating to 2,300-1,800 years ago were genetically related to the descendants of the southern Khoe-San groups, and the four younger individuals who lived 500-300 years ago were genetically related to current- day South African Bantu-speaking groups.
“This illustrates the population replacement that occurred in southern Africa,” said Carina Schlebusch, population geneticist at Uppsala University in Sweden.
Researchers estimate the divergence among modern humans to have occurred between 350,000 and 260,000 years ago, based on the ancient Stone Age hunter-gatherer genomes.
The deepest split time of 350,000 years ago represents a comparison between an ancient Stone Age hunter-gatherer boy from Ballito Bay on the east coast of South Africa and the West African Mandinka.
“This means that modern humans emerged earlier than previously thought,” said Mattias Jakobsson, population geneticist at Uppsala University.
The fossil record of east Africa, and in particular the Omo and Herto fossils, have often been used to set the emergence of anatomically modern humans to about 180,000 years ago.
The deeper estimate for modern human divergence at 350,000-260,000 years ago coincides with the Florisbad and Hoedjiespunt fossils, contemporaries of the small-brained Homo naledi in southern Africa.
“It now seems that at least two or three Homo species occupied the southern African landscape during this time period, which also represents the early phases of the Middle Stone Age,” said Marlize Lombard, from University of Johannesburg in South Africa.
Researchers also found that all current-day Khoe-San populations mixed with migrant East African pastoralists a little over a thousand years ago.
Of the Iron Age individuals, three carry at least one Duffy null allele – a gene mutation protecting against malaria, and two have at least one sleeping-sickness- resistance variant gene.
The Stone Age individuals do not carry these protective alleles.
“This tells us that Iron Age farmers carried these disease-resistance variants when they migrated to southern Africa,” said Helena Malmstrom, archaeo-geneticist at Uppsala University.
Archaeological deposits dating to the time of the split by 350,000-260,000 years ago, attest to South Africa being populated by tool-making hunter-gatherers at the time, researchers said.
Though human fossils are sparse, those of Florisbad and Hoedjiespunt are seen as transitional to modern humans, they said.
These fossils may therefore be ancestral to the Ballito Bay boy and other San hunter-gatherers who lived in southern Africa 2,000 years ago.