A stretch of Neanderthal DNA passed down through interbreeding thousands of years ago may still be shaping the bodies of some humans today, making carriers more muscular and giving them a slightly different build than people without the ancient variant.
A new study found that this Neanderthal DNA changes how a key growth hormone receptor works, and people who carry it tend to be more muscular. The study, led by Philipp Kanis of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, was published in the journal Current Biology. The focus was a gene known as GHR, which is responsible for the receptor that responds to growth hormone and helps control bone and muscle development.
How Neanderthal DNA makes some humans more muscular
According to the study, Neanderthals possessed two particular variations to this gene not found in modern humans from Africa. These made their way into the human gene pool when Neanderthals and modern humans interbred, likely tens of thousands of years ago.
Today, the variant is essentially missing in African populations but shows up more often in Asia, reaching its highest known frequency, about 24%, in Pakistan. Kanis and colleagues analyzed genetic and health data from more than a million adults across several biobanks.
People who carried the Neanderthal version of the gene were on average taller and heavier with increased muscle mass in their arms, legs, and trunk in comparison to non-carriers. The researchers also linked the variant to certain facial and dental traits associated with Neanderthals, including a shorter lower jaw bone, a higher chance of an overbite, and somewhat shorter tooth roots.
Lab tests reveal why the Neanderthal receptor boosts muscle cell growth
The team tested the Neanderthal version of the receptor in lab-grown cells to determine how this Neanderthal-linked variance results in increased muscle mass. Cells carrying the Neanderthal variant grew faster and produced more of a signaling protein called STAT5 than cells with the modern human version, when exposed to growth hormone.
A difference in a single amino acid in the receptor was found to be the cause according to researchers. Notably, this was related to the growth hormone produced by the pituitary gland after birth. It did not appear with the version made by the placenta during pregnancy. This may explain why the study found no link between the variant and birth weight.
The researchers noted that most of the effects on height and weight appear later in life, showing up in adults but not in children up to age eleven, suggesting the variant becomes more active around puberty, when growth hormone levels rise sharply.
The findings add to a growing body of evidence that ancient interbreeding with Neanderthals continues to be influential in the health and physique of people to this day.
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