New research from the Max Planck Institute for Evolutionary Anthropology reveals that a genetic variant inherited from Neandertals contributes to increased muscle mass in modern humans. The study, published in Current Biology, identifies two specific changes in the growth hormone receptor that were passed down to humans roughly 47,000 years ago.
Laboratory tests on cells carrying this Neandertal variant showed a 40 percent stronger response to growth hormone compared to the standard human receptor. This finding aligns with data from over a million individuals, confirming that the impact on body composition is measurable in adults, who carry approximately 270 grams more muscle mass on average.
Interestingly, the physical effects of this gene do not appear during childhood. Researchers noted that growth patterns remain consistent among children until around age eleven, suggesting the influence of the receptor likely kicks in during puberty when growth hormone levels surge.
The prevalence of this genetic trait varies significantly across different global populations. It appears most frequently in South and East Asian groups, where up to 24 percent of the population may carry the variant, while it remains much rarer in European populations at only 0.5 percent.
Beyond muscle mass, the researchers identified subtle links to skull and tooth development, including a shorter rear section of the lower jaw and shorter tooth roots. Experts emphasize that this genetic contribution is just one part of the complex puzzle that determines human physical traits, and it does not dictate a person's entire physical profile.