A study published in Current Biology identifies a specific gene inherited from Neanderthals that influences muscle mass in modern humans today. Researchers discovered that this gene, which controls the growth hormone receptor, originated from interbreeding between Neanderthals and early humans roughly 47,000 years ago. While the gene is rare in populations of European ancestry, it appears with significantly higher frequency in South and East Asian populations, reaching about 24 percent in some groups.
To understand the mechanics, the team tested the Neanderthal receptor against the standard modern human version in laboratory cells. The results showed that cells carrying the Neanderthal receptor grew 40 percent faster when exposed to growth hormone. This mechanism increases activity in the JAK2-STAT5 signaling pathway, which is critical for cellular growth. One specific amino acid change within the receptor appears to be the primary driver of this increased sensitivity.
Data from human subjects confirms the impact of this genetic legacy. Adults who carry a copy of this Neanderthal gene variant typically possess around 271 grams of additional muscle mass compared to those without it. Interestingly, these physical differences do not manifest during early childhood. The effects become apparent during puberty when growth hormone levels naturally spike, suggesting the gene exerts its most significant influence during adolescent and adult development.
Beyond muscle mass, the researchers linked the gene to minor anatomical traits consistent with Neanderthal features. Carriers of this variant showed a higher incidence of overbites, shorter tooth roots, and slight differences in lower jaw structure. The study indicates that while this single gene does not account for the entire Neanderthal body shape, it serves as a clear example of how ancient genetic history continues to influence human biology. The researchers noted that because other genes sit in close proximity to the growth hormone receptor on the DNA segment, they are continuing to investigate whether nearby genetic changes also contribute to these observed physical traits.