Neanderthals are known to have had physiological differences from Homo sapiens, including thicker bones and defined brow ridges, as in this model.Credit: Mike Kemp/In Pictures via Getty
Two genetic changes in the genomes of Neanderthals contributed to the extinct hominin’s characteristic robust physique — and the differences persist in modern humans. The variants make carriers taller and more muscular than non-carriers, according to a study1 published in Current Biology.
Neanderthals, who lived across Europe and western Asia from about 300,000 years ago to around 40,000 years ago, interbred with Homo sapiens before going extinct. Previous studies have shown that modern humans with ancestors from outside Africa inherited roughly 1–4% of their DNA from Neanderthals2.
Fossil evidence shows that Neanderthals had broader chests3, thicker bones4 and larger muscles than most modern humans do. The latest study provides a plausible molecular pathway that contributed to the Neanderthals’ robust traits, says Bastien Llamas, a human geneticist at Adelaide University in Australia.
Echoes of an ancient genome
Well-preserved Neanderthal remains are extremely rare and, so far, scientists have recovered only about five genetic samples of sufficient quality to reconstruct a full or near-complete genome. Most Neanderthal DNA samples are fragmented and yield only partial sequences.
The researchers focused on the growth hormone receptor, which helps to regulate bone and muscle growth. The team used three high-coverage and two medium-coverage Neanderthal genomes to identify two amino-acid changes unique to the growth hormone receptor in these hominins.
They found that the receptor variant entered modern populations through interbreeding around 47,000 years ago. Today, about 20% of the population in South Asia and 15% in East Asia carry it. By contrast, these genetic differences are present in just around 0.5% of Europeans, and are absent in people from sub-Saharan Africa.
To test whether these ancient changes altered the receptor’s function, the team engineered mouse cells to produce either the Neanderthal or the modern human version of the receptor. Cells carrying the Neanderthal receptor proliferated around 39% more over five days than did cells carrying the variant that is dominant in modern humans.
The team also looked at population data sets from five biobanks, analysing health and genetic data from more than 1.1 million adults. On average, people carrying the Neanderthal-derived variant were around 0.3 centimetres taller than those who did not have it.
People who carry this variant also have 0.25 kilograms more muscle mass than those who don’t, says co-author Philipp Kanis, a genetics researcher at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
The most interesting aspect of the study is the convergence of ancient genomics, experimental cellular biology and present-day biobank traits, says Llamas. It provides an unusually detailed example of how DNA inherited from Neanderthals can affect a defined molecular pathway and contribute to measurable variation in present-day humans, he adds.
The ancient variant was also associated with several craniofacial features. Modern humans with the gene variant tended to have a shorter ramus — the rear portion of the lower jaw — as well as a greater chance of an overbite and shorter tooth roots than non-carriers.
