Laboratory tests in mouse cells reveal the Neanderthal receptor variant drives about 40% greater growth response to growth hormone, mainly due to one of two DNA changes identified between Neanderthal and modern sequences.

Carrying one copy from each parent could add about 0.5 kilograms of muscle mass, but this variant is not a substitute for training.

Overall, puberty may amplify the variant’s impact as growth hormone dynamics change, though the onset varies among individuals.

The research is led by Hugo Zeberg and Philipp Kanis, with publication in Current Biology in 2026 and collaboration with Newsweek.

The work underscores the continued value of science journalism and curiosity about how ancient genetics influence modern human biology.

Although the lab-estimated 40% signaling boost is clear, it does not translate directly to large real-world effects; the average impact remains modest.

A Neanderthal-derived variant of the growth hormone receptor increases cellular response to growth hormone, contributing to muscle mass differences in carriers.

Population data from over 1.1 million adults across five biobanks show carriers have about 270–285 grams more lean mass and rise roughly 0.3 centimeters taller on average, indicating small but detectable effects on body composition.

The effect appears to emerge later in development, around puberty, with no associations observed in children up to age 11 in a dataset of over 6,000 kids.

Experts note that the lab results align with population data, supporting a real but small effect in people.

This single genetic change is only one piece of a complex puzzle, with many factors shaping growth and body form.

The Neanderthal variant cannot fully explain the overall body type or appearance, as multiple genetic and environmental factors are involved.