Neanderthal muscle-boosting gene shows up in some modern humans, but it's rare
Researchers report a Neanderthal variant of the growth hormone receptor gene that enhances how modern humans respond to growth hormone. Interbreeding occurred roughly 47,000 years ago, and the variant now appears in about 10% of people (up to ~25% in certain Asian populations) with little presence in Africans. In lab tests, cells bearing the Neanderthal receptor multiplied ~40% more when exposed to growth hormone, translating to roughly 270 grams of extra muscle per copy (more than a kilogram with two copies). The effect seems to emerge mainly during puberty and is a subtle contributor to body form, not a sole explanation for Neanderthal robustness.