According to a study published in the PLOS One journal, Neanderthal blood samples revealed that their blood contained a specific set of genetic variants that made them susceptible to foetal and newborn haemolytic disease (HDFN). This HDFN, according to researchers, can cause anaemia, which usually worsens with the second, third, and subsequent pregnancies.
They believe that as a result, the number of Neanderthal children has decreased.
‘Analyses of blood group systems of Neanderthals and Denisovans contributed to a better understanding of their origin, expansion and encounters with Homo sapiens,’ the report said.
Although this could have happened as a result of only Neanderthals having sexual relationships, the risk of HDFN is said to be higher in cases of human ancestors having sexual relationships with Neanderthals.
‘These elements could have contributed to weakening the descendants to the point of leading to their demise, especially combined with the competition with Homo sapiens for the same ecological niche,’ the report claims.
While the disorder is now considered extremely rare in humans, it is still considered common in Neanderthals due to the species’ small gene pool.
‘The fact that these forms of genes were detected in individuals separated by 4,000km and 50,000 years suggest that this genetic peculiarity — and the risk of [an] anaemic foetus — would have been quite common amongst Neanderthals,’ Stephane Mazieres, a lead author on the research from Aix-Marseille University was quoted saying by the Daily Mail.