Researchers identified a Neanderthal-derived variant of the growth hormone receptor gene that is present in some modern human populations.
Laboratory experiments showed that this variant alters receptor function in a way that promotes muscle growth.
The team then cross-referenced these molecular findings with genetic and body-composition data from large population cohorts.
Individuals carrying one copy of the variant had, on average, 271 grams more muscle mass than non-carriers.
Those who inherited the variant from both parents showed an even greater increase in muscle mass.
The study combined cellular assays with population-scale genomic analysis to establish the link between the ancient variant and a measurable physiological trait today.
The variant is relatively common in certain ancestry groups, reflecting its persistence since interbreeding between Neanderthals and early modern humans.
Researchers caution that the variant explains only a small fraction of overall variation in muscle mass and that environmental factors such as exercise and nutrition remain dominant determinants.
Your Neanderthal genes may be building your muscles
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