A recent blood group analysis of three Neanderthals and one Denisovan confirm their African origin, Eurasian dispersal, and interbreeding with early Homo sapiens. Intriguingly, it also added evidence of low genetic diversity and possible demographic fragility.Neanderthals and Denisovans are extinct hominin lineages but were present throughout Eurasia from 300,000 to 40,000 years ago. In three of the individuals, the presence of a ‘non-secretor’ allele, associated with protection from certain viruses, suggests selective pressure exerted by the latter. / Prüfer et al. These clues strengthen the hypothesis that low genetic diversity together with low reproductive success contributed to the disappearance of Neanderthals.