Inherited Neandertal gene variant increases muscle mass in modern humans

Neandertals were generally more strongly built than most people living today. Their bones show signs of large muscles, and they had characteristic features such as prominent brow ridges and relatively short tooth roots.

Growth hormone helps shape the body by regulating the growth of muscles and bones. It is released by the pituitary gland at the base of the brain and travels through the bloodstream. To act on a cell, the hormone must bind to a receptor on its surface, which then passes the signal into the cell.

An international team led by Hugo Zeberg of Karolinska Institutet and Philipp Kanis of the Max Planck Institute for Evolutionary Anthropology found that the Neandertal version of this receptor has two changes that are not present in the version most common in modern humans.

Neandertal variant responds more strongly to growth hormone

The study shows that laboratory-grown cells with the Neandertal receptor responded more strongly to growth hormone. They grew 40 percent more than cells with the more common modern human receptor. The researchers linked most of this stronger response to one of the two Neandertal-specific changes.

Modern humans inherited this version of the receptor through interbreeding with Neandertals around 47,000 years ago. Today, it is particularly common in South and East Asia. Up to 24 percent of people in some South Asian populations carry it, compared with around 0.5 percent of Europeans.

What struck me most was that two very different types of evidence told the same story. Cells grown in the laboratory responded more strongly, while data from more than a million people showed signs of the same effect in the body. It is rare to see laboratory and population evidence fit together so clearly.”

Philipp Kanis, first author of the study and postdoctoral researcher, Max Planck Institute for Evolutionary Anthropology

Differences first become apparent after childhood

The difference appears to emerge only after childhood. The researchers examined body measurements from more than 6,000 children and found no link between the Neandertal version and growth up to the age of eleven. This suggests that its effects may become noticeable later, possibly around puberty, when growth hormone levels increase substantially. Among adults, people carrying the Neandertal version had, on average, around 270 grams more muscle mass.

“As someone who does CrossFit, I was delighted to find Neandertal genetics and muscle mass coming together in the same study,” says co-author Miriam Berreiter. “But even a Neandertal growth hormone receptor is no substitute for training.”

The Neandertal version was also linked to subtle differences in the skull and teeth. Carriers tended to have a slightly shorter rear section of the lower jaw and shorter tooth roots. Both features are closer to what was typical of Neandertals.

“It is fascinating that one genetic change inherited from Neandertals can still have an effect on the human body today,” says Hugo Zeberg, senior author of the study. “But this is only one of many genetic influences on growth and body shape. It cannot explain the Neandertal body type on its own, and it certainly does not determine a person’s overall appearance.”