Neanderthal heritage gave humans a little more muscle mass

A study has revealed that individuals carrying genetic material inherited from Neanderthals may possess slightly more muscle mass compared to those without such ancestry. This finding comes from research examining a specific variant of the growth hormone receptor gene, which suggests a subtle influence on body composition. However, researchers emphasize that this effect is minimal and largely overshadowed by other factors influencing muscle development. The study focused on a particular segment of DNA inherited from Neanderthals, specifically a version of the growth hormone receptor gene. Scientists analyzed how this genetic variation might affect human physiology. The research team, led by Philipp Kanis from the Max Planck Institute for Evolutionary Anthropology in Leipzig and Hugo Zeberg from the Karolinska Institute in Sweden, conducted experiments using mouse cell cultures to observe the impact of different receptor variants on cellular growth. In their experiments, both the Neanderthal-derived and modern human versions of the receptor were introduced into cells that lacked the ability to produce the growth hormone receptor. Both variants bound to the hormone equally well, but differences emerged after five days. Cells with the Neanderthal variant showed a 39 percent increase in cell count, primarily due to a specific amino acid change at position 561. This alteration increased the growth rate by six percent and enhanced the activation of the signaling molecule STAT5 by 22 percent. The genetic segment under investigation dates back approximately 47,000 years and is present in varying frequencies among populations today. In South Asia, around 20 percent of individuals carry this genetic marker, while in a sample from Pakistan, the prevalence was 24 percent. In East Asia, the figure stands at 15 percent. In Europe, however, only 0.5 percent of the population carries this variant, and it is absent entirely in populations south of the Sahara. The study also examined physical characteristics associated with the genetic variant. Researchers noted that individuals carrying the Neanderthal-derived receptor variant tended to have a shorter posterior section of the lower jaw and shorter tooth roots. These findings suggest potential morphological differences linked to the genetic inheritance from Neanderthals. To assess possible effects on human body composition, the research team analyzed data from over 1.1 million adults across five biobanks and a British birth cohort comprising 6,602 children. The analysis aimed to determine whether the presence of the Neanderthal-derived receptor variant correlated with observable differences in muscle mass or other physical traits. While the study identified a statistical association, the effect size remained small, indicating that environmental and lifestyle factors play a dominant role in shaping human physique. The discovery adds to the growing understanding of the genetic legacy left by Neanderthals in modern humans. Previous studies have identified several genetic regions inherited from Neanderthals that influence susceptibility to diseases such as severe COVID-19, pain perception, and connective tissue disorders. This new research highlights another potential physiological trait influenced by ancient interbreeding events. The timing of the interbreeding between Neanderthals and early modern humans is estimated to have occurred roughly 47,000 years ago, based on two independent studies published in 2024. While the exact geographic location of these interactions remains uncertain, Southwest Asia is considered a likely region due to the coexistence of both hominin species during that period. Despite the identification of specific genetic influences, scientists caution that the overall impact of Neanderthal DNA on human biology is complex and multifaceted. Many inherited genetic segments have been lost over time, while others have been retained and adapted through evolutionary processes. The current study contributes to ongoing efforts to map the functional consequences of ancient genetic exchanges, offering insights into how our ancestors' biological traits continue to shape contemporary human diversity.