About one in five people carries a genetic variant that increases resistance to low temperatures. A study published in the American Journal of Human Genetics confirmed this experimentally.
We are talking about variants of the ACTN3 gene, which is responsible for the synthesis of the muscle protein alpha-actin-3. The majority of the world's population has a variant of this gene, in which the body produces the corresponding protein. But approximately one and a half billion people are carriers of another variant; they lack this protein.
Scientists assumed that the ACTN3 gene had a role in evolution. Perhaps many millennia ago, the absence of alpha-actin-3. helped people survive in the cold climate of Europe. An international group of scientists tested this hypothesis experimentally.
The new study involved 42 healthy men. In the experiment, they had to be immersed in cold water, after which scientists objectively assessed how much each of them froze. The water temperature was 14 degrees, cooling could last up to 120 minutes or until the core body temperature reached 35.5 degrees Celsius.
Only 30% of participants in whose bodies alpha-actin-3 was present were able to endure the cold test completely, for 120 minutes. Of the people with a deficiency of this protein, 69% completed the full cooling cycle. Scientists found that people from the second group shivered less from the cold compared to participants from the first. They suggest that not shivering helps maintain heat and energy.
What is this protein?
Alpha-actin-3 protein synthesized in fast muscle fibers, which are responsible for fast and strong muscle contractions. Its absence is known to be associated with decreased sprinting ability in humans, but increases muscular endurance. This increase in endurance may enhance the ability to conserve energy and withstand cold. The authors of the new study believe it supports the hypothesis that a particular variant of the ACTN3 gene helped humans survive migration more than 50 thousand years ago.