It’s no secret that modern humans and Neanderthals interbred: most of the world’s population today has around 1 or 2 percent of Neanderthal DNA. Now a new study suggests that, for some of us, our muscles may get a boost from Neanderthal genetics. Researchers looked at differences between the modern human and Neanderthal genomes and identified distinct genetic changes in Neanderthals’ growth hormone receptor—a key cell protein that helps regulate growth throughout the body. In lab experiments, cells with the Neanderthal receptor grew more than cells with the modern human version. People who carry at least one Neanderthal version of the receptor tend to have more muscle than those who don’t—271 additional grams, the authors report.