Neanderthals passed on a gene that helps modern humans pack on more muscle — but only a few people have it

Tens of thousands of years ago, Neanderthals mated with modern humans and passed along a gene variant that enables us to pack on more muscle, a new study finds.

Researchers found that this specific Neanderthal gene, a variant of the growth hormone receptor gene, causes cells to respond strongly to growth hormone. The Neanderthal version of the gene creates a growth hormone receptor with two amino acid changes and one deletion, compared with the typical receptor in most modern humans. The researchers think it entered the modern human gene pool through interbreeding, probably about 47,000 years ago.

"The most noticeable characteristic would likely be greater muscle mass, around 270 grams [9.5 ounces] per copy of the variant," study co-author Hugo Zeberg, a geneticist at the Karolinska Institute in Sweden, told Live Science in an email. "A person who inherited two copies, one from each paren...