An international team led by Hugo Zeberg of Karolinska Institutet and Philipp Kanis of the Max Planck Institute for Evolutionary Anthropology announced on Aug. 5 that a Neandertal gene variant inherited by some modern humans is associated with increased muscle mass. The researchers found that the Neandertal version of the growth hormone receptor has two changes not present in the version most common in people today.
Laboratory tests showed that cells with this Neandertal receptor responded more strongly to growth hormone, growing 40 percent more than cells with the typical human receptor. Most of this stronger response was linked to one specific change unique to Neandertals.
The study reports that modern humans inherited this genetic variant through interbreeding with Neandertals around 47,000 years ago. It is now particularly common in South and East Asia, where up to 24 percent of people in some South Asian populations carry it, compared with about 0.5 percent among Europeans.
Researchers examined body measurements from over 6,000 children and found no connection between the Neandertal gene and growth before age eleven. This suggests its effects may become noticeable after childhood, possibly during puberty when growth hormone levels rise significantly. Among adults, carriers had on average about 270 grams more muscle mass than non-carriers.
Co-author Miriam Berreiter said, "As someone who does CrossFit, I was delighted to find Neandertal genetics and muscle mass coming together in the same study," adding that "even a Neandertal growth hormone receptor is no substitute for training." The variant was also linked to subtle differences in skull shape and tooth roots—features closer to those typical of Neandertals.
"It is fascinating that one genetic change inherited from Neandertals can still have an effect on the human body today," Zeberg said. "But this is only one of many genetic influences on growth and body shape. It cannot explain the Neandertal body type on its own, and it certainly does not determine a person's overall appearance."
