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. We know a little about how that genetic ancestry influences our bodies today—the immune system for example—but there’s still much we don’t know.

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 genome and identified distinct genetic changes in Neanderthals’ growth hormone receptor—a key cell protein which helps regulate growth throughout the body. In lab experiments, cells with this receptor grew more than cells with the modern human version. The results could help explain Neanderthals’ “robust build,” the authors write.

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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. People who inherit the trait from both parents often have even more muscle mass. According to the study, the variant is most common in populations in South and East Asia, with as many as 24 percent carrying a Neanderthal version of the receptor.

“It is rare to see laboratory and population evidence fit together so clearly,” Philipp Kanis, the first author of the study and a postdoctoral researcher at the Max Planck Institute for Evolutionary Anthropology, in Germany, said in a statement. “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.”

If you aren’t among those blessed with this genetic gift, there’s still the gym.

“As someone who does CrossFit, I was delighted to find Neandertal genetics and muscle mass coming together in the same study,” said Miriam Berreiter, a study coauthor and a PhD student at the Karolinska Institute, in Sweden, in the same statement. “But even a Neandertal growth hormone receptor is no substitute for training.”

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