Kenneth Glad
Researchers have identified a small difference in adult body composition linked to an ancient genetic variant. Laboratory experiments suggest the change alters the way cells respond to growth hormone.
Neanderthals disappeared tens of thousands of years ago, but they did not vanish without leaving a genetic legacy. Because Neanderthals and early modern humans interbred, many people today still carry small amounts of Neanderthal DNA. Scientists are continuing to investigate whether some of those inherited variants influence traits in people living now.
One of those variants has now been linked to subtle differences in body size and muscle mass. Research involving more than 1.1 million adults found that each copy of the Neanderthal-derived variant was associated with about 285 grams of additional body weight. Roughly 271 grams of that difference was muscle, while carriers were also about 0.30 centimeters taller per copy. The effect is small for an individual, but a dataset of this size allowed researchers to detect the pattern.
The DNA segment contains a Neanderthal version of the gene that encodes the growth hormone receptor. This receptor helps cells respond to growth hormone, which is involved in physical development. Researchers led by Hugo Zeberg of Karolinska Institutet and Philipp Kanis of the Max Planck Institute for Evolutionary Anthropology estimate that the sequence entered modern human populations through interbreeding around 47,000 years ago.
The study appeared online in Current Biology on August 5, 2026, and was furthermore covered by Historienet. By examining how this ancient version of the receptor behaves, the researchers were able to explore why a piece of DNA inherited from Neanderthals may still be associated with measurable differences in the human body today.
The signal works differently
To test the ancient receptor directly, the scientists compared it with the form most common among people today. After growth hormone was introduced, laboratory cells carrying the Neanderthal version proliferated about 40 percent more. The experiment gave researchers a way to examine the receptor’s effects separately from the many other factors that influence growth in living people.
The two receptor forms differ at only two amino-acid positions. Follow-up experiments indicated that one of those substitutions was responsible for most of the stronger cellular response, helping narrow down which genetic change appears to matter most.
The study also identified associations beyond muscle and height. Carriers tended to have shorter tooth roots and modest differences in part of the lower jaw. The variant is distributed unevenly around the world, appearing mainly in South and East Asia. In some populations, up to 24 percent of people carry it, compared with only about 0.5 percent in Europe.
The age at which its effects become noticeable remains uncertain. An analysis of more than 6,000 children found no comparable relationship through age 11. The authors suggest that the difference could emerge later in development, possibly around puberty, although the available evidence does not establish exactly when the adult pattern begins.
One factor among many
The researchers caution against treating the variant as a major determinant of physique. Growth, height and muscle mass are shaped by many genes acting together, while environmental influences also contribute to the differences seen between individuals. Nutrition, general health and physical activity can all affect how the body develops over time.
The Neanderthal-derived variant therefore represents only one small part of a much broader biological picture. Its average effect is measurable across very large groups, but it does not determine how tall or muscular any individual person will become.
Co-author Miriam Berreiter also stressed that carrying the Neanderthal-derived version does not replace training. Although the variant is associated with slightly greater muscle mass on average, exercise remains far more important for building and maintaining a muscular body. Genetics may provide a small underlying difference, but lifestyle still plays a central role in the final outcome.
Sources: Current Biology, Historienet
