The Neanderthal in You Still Works Out: Ancient Gene Tied to Bigger Muscles

LEIPZIG, GERMANY — The Neanderthals have been extinct for roughly 42,000 years, but their gym membership, it turns out, never lapsed.

A new study led by scientists at the Max Planck Institute for Evolutionary Anthropology finds that a Neanderthal version of the growth hormone receptor — the protein that tells the body how hard to respond to growth hormone — is still circulating in some living humans, and that it does more than the modern human version. The finding, published in Current Biology, is the latest entry in the long-running conversation between modern genetics and its prehistoric co-author.

The receptor, known in the trade as GHR, is the part of the system that receives the growth hormone released by the pituitary gland and translates it into action. The Neanderthal version, as the researchers describe it, carries two amino acid changes that are not found in people of African ancestry today. When the scientists inserted the Neanderthal receptor into lab-grown cells and exposed the cells to growth hormone, the cells multiplied faster and showed stronger downstream signaling than cells carrying the modern human version. In the language of the lab bench, the caveman version works harder.

The mechanism is the one that has made the last decade of genetics what it is: interbreeding. Before the Neanderthals disappeared, they interbred with the ancestors of modern non-Africans, and the result is that people with non-African roots carry, on average, about two percent Neanderthal DNA. Two percent is, by the arithmetic of the genome, a small number. By the arithmetic of the gym, it is apparently a head start.

Using genetic and health data from more than a million people across multiple biobanks, the researchers found that adults carrying the Neanderthal variant of the receptor tend to be slightly taller and slightly heavier than non-carriers — with the added weight, importantly, being muscle. The study’s authors are careful to note that this one receptor, standing alone, “cannot explain the Neanderthal body type,” which is the scientific way of saying that the subscription includes the muscle but not, at this time, the brow ridges, the barrel chest, or the occipital bun at the back of the skull, all of which the fossil record shows the species had in abundance.

The Neanderthal profile, for the record, is the one that has made the species the fossil record’s most famous gym rat: a robust build, a barrel-shaped thorax, greater muscle mass than modern humans, and teeth with unusually short roots, a condition researchers call, with the enthusiasm of people who name things for a living, taurodontism.

The practical implications, to the extent they exist, are a matter of some interest to the fitness industry, which has a long history of treating peer review as a lead-generation event. The study itself stops short of recommending that anyone go look for their two percent, and its authors stop even earlier, at the point where a gene that nudges muscle mass in a population study is not, by itself, a prescription, a promise, or a reason to skip leg day.

It is, however, a reason to reconsider the mirror. That strength you have been trying to build for years may, in part, be 42,000 years old, and it may have been in the building the whole time, waiting for a growth hormone to call.

At press time, the fitness industry had not responded to requests for comment on whether it would begin selling what the trade is already calling “archaic admixture packages,” which is to say that the marketing departments are moving at the speed of peer review, and peer review, as the study demonstrates, takes about 42,000 years.