How to give a Neanderthal a blood transfusion
Genetic study of blood types reveals connection between human ancestors and Indigenous Australians.
It began as a joke. A paleoanthropologist, a geneticist and a blood specialist were hanging around an espresso machine – and one of them wondered: how would you give a Neanderthal a blood transfusion?
They reported their surprising results in PLOS 1. For one thing, transfusing a Neanderthal with human blood would be a bad idea. Because of the mismatched Rh types, there’s a one-in-five chance of producing a baby with haemolytic disease. “That might explain why Neanderthal-human inbreeding was limited,” says paleoanthropologist and lead author Silvana Condemi.
The researchers focused on the seven major blood groups that are used today to match donors and recipients. Blood groups represent collections of tags – think of them as differentcoloured “post its” – that are carried on the surface of red blood cells. They consist of ABO, Rhesus (Rh), Kell, Duffy, Kidd, MNS and Diego.
The team drilled down into the high-quality genomes of three Neanderthals and a Denisovan. The Neanderthals included two Siberians: the 100,000-year-old Altai female who lived in Denisova Cave, and a 48,000-year-old female from Chagyrskaya Cave. A third female aged about 57,000 years came from Vindija Cave in Croatia. The Denisovan genome came from a female who lived in Denisova Cave about 64,000 years ago.
The first surprise was discovering that the full variability of the ABO system seen in modern humans was present in the Neanderthals. “We thought for years that H. sapiens was the only one to have the full set,” says Condemi. Chimpanzees are all type A; gorillas are all type B. Until this study the only Neanderthal to be checked was blood type O.
The next surprise was that all three Neanderthals carried a rare Rhesus type which Condemi refers to as “Rhesus plus incomplete”. This variant had only ever been seen once before. In 2019, researchers analysing the DNA of 72 Western Desert Aboriginal people found that one of them carried the same novel Rhesus type.
“At the time, it was assumed to be a new Rhesus type that had arisen in Australia,” says Condemi. “Now we know that it had existed in the past and was lost.”
The finding confirms the evidence from DNA (all non-africans carry about 2% Neanderthal DNA) that modern humans interbred with Neanderthals in the Middle East before heading to south Asia and Australia.
The findings also give clues as to the Neanderthals’ disappearance. The fact that three Neanderthals separated by 50,000 years in time and
5,000 km of space all shared the same Rhesus type adds to the evidence from genome studies of their low genetic diversity.
But interbreeding with modern humans could have put them at risk of another kind. Condemi says that if an Rh “partial complete” Neanderthal mated with an Rh-complete
H. sapiens, there would be an 18% chance of the infant developing the condition known as “haemolytic disease of the newborn” and dying.