Evrim Yazgin
Cosmos science journalist
Early humans underwent adaptive genetic changes in their blood groups after leaving Africa, according to new ancient DNA analysis.
Researchers analysed the blood groups of 22 Homo sapiens (modern human), 14 Neanderthals and one offspring of a Neanderthal and a Denisovan – another archaic human species. The individuals lived between 120,000 and 20,000 years ago.
Findings published in the journal Scientific Reports suggest that new rhesus, Rh, (RHD and RHCE) alleles emerged after early humansleft Africa but before they spread across Eurasia.
Rhesus is a type of protein found on the outside of red blood cells.
Understanding how blood groups developed over time could help in determining human migration patterns and how ancient humans intermixed and how this interbreeding impacted their genetics.
It is known that Homo sapiens and Neanderthal met and interbred with Neanderthals in West Asia from about 100,000 years ago.
Neanderthal had ancestral alleles similar to those found in modern populations of people living in sub-Saharan Africa. But early Homo sapiens had developed new Rh alleles which today are crucial blood types in transfusion and pregnancy monitoring.
Because these alleles aren’t present in Neanderthal, it suggests that they developed after H. sapiens left Africa.
The study also found 3 alleles absent from modern-day humans. These could belong to a lineage whose ancestry did not contribute to present-day Eurasian populations.
“H. sapiens could have resided long enough in the Persian Plateau to differentiate”, the authors write. These new alleles may have provided an evolutionary advantage to early modern humans who confronted different environmental and selection pressures than populations who remained in Africa.
On the flip side, Neanderthal had an Rh type, RhD, that exists in modern humans only very rarely. It is a type which is not compatible with other variants found in H. sapiens and Denisovans.
Such incompatibility could have led to disease if Neanderthal interbred with these other ancient humans. It could have been a contributing factor in the demise of Neanderthals.
