Our species evolved in Africa. But after examining the genome of a 35,000-year-old human skull unearthed in Romania, researchers say some populations migrated back to northern Africa from western Asia during the Early Upper Paleolithic starting around 45,000 years ago. The findings were published in Scientific Reports last week.
Anatomically modern humans dispersed out of Africa some 70,000 to 50,000 years ago, and by around 45,000 to 40,000 years ago, human ancestors resembling Homo sapiens today appeared in the western Eurasian fossil record. Recent analyses on the distributions of modern-day haplogroups – a genetic population that shares a common ancestor – suggest that during the Eurasian expansion, some populations initiated a "back-migration" to northern Africa. The genome of a 4,500-year-old Ethiopian individual suggested that the journey from Eurasia back to Africa had already occurred by then. But until now, there’s been a scarcity of even older human fossils from northern Africa to support this back-migration.
The skull of a female from Peştera Muierii ("Cave of the Old Woman") was discovered in 1952 near Baia de Fier in Gorj County, Romania. Radiocarbon dating puts the skull at 35,000 years old. Called PM1, the specimen corresponds fully to Homo sapiens, but does exhibit a mix of modern human and Neanderthal features.
After extracting DNA from two of the teeth, a team led by Concepcion de-la-Rua from the University of the Basque Country (UPV/EHU) was able to sequence her mitochondrial genome (or mitogenome). They found that PM1 belongs to a haplogroup that hasn’t been identified before in any humans, ancient or modern. They called it U6 basal* and it originated in Eurasia.
This newly identified basal lineage has now disappeared, but haplotypes derived from it can be found today – mostly in northwestern African populations. The U6 lineage likely diversified during the back-migration, up until present-day U6 African lineages emerged. Derived U6 haplotypes now found in Europe were likely due to much more recent gene flow from Africa.
PM1 likely belonged to an offshoot to southeastern Europe of the Early Upper Paleolithic migration from Asia back to Africa.
The team is now analyzing the nuclear genome.