How people became runners
A single mutation allowed ancient people to become marathon runners
Ekaterina Rusakova, N+1
American researchers have found that human endurance and their ability to run long distances may be associated with a single mutation that appeared 2-3 million years ago, according to the Proceedings of the Royal Society B (Okerblom et al., Human-like Cmah inactivation in mice increases running endurance and decreases muscle fatigue: implications for human evolution). Apparently, it affected the ability of skeletal muscles to use oxygen more efficiently and, as a result, to get tired less.
The genus Homo appeared in the period 2-3 million years ago, when savannas began to appear on the site of tropical forests. Ancient people adapted to the transition from an arboreal to a terrestrial lifestyle, learning to move on two limbs and run. As a result, modern humans have become the hardiest runners among primates and one of the hardiest runners among animals in general. Probably, the ability to run long distances allowed ancient people to hunt for a long time and over large territories.
At the same time, when ancient people became hardy runners, they had a mutation in the CMAH gene and "turned off" the enzyme CMP-Neu5Ac hydroxylase encoded by this gene. Hydroxylases attach a hydroxyl group (-OH) to a substance specific to them. As a result, glycolylneuramic acid, a substance that is part of the cell membrane and participates in intercellular interactions, including in the interaction of body cells with pathogens, has ceased to be produced in the human body. Probably, as a result, ancient people developed resistance to certain diseases and the mutation became entrenched in the population. It has led to other changes: apparently, people have an increased risk of getting chronic inflammation, but at the same time the ability to absorb oxygen has increased. Studies have shown that in mice with a "human" mutation in the SMANi gene with hydroxylase "turned off", oxygen consumption increases and muscle fatigue decreases.
Scientists from the University of California at Davis, led by Professor Ajit Varki, suggested that a mutation in the CMAH gene could affect the development of endurance of ancient people and their ability to run long distances. To show this, the researchers conducted experiments on mice with a mutation in the CMAH gene. They used ordinary mice as a control. The animals were placed in a running wheel for two days in a row and they had to turn it for ten minutes. At this time, scientists measured their speed and endurance. In another test, mice were allowed to run in a wheel every day for 15 or 30 days and their activity was monitored. Then the animals were sacrificed and their muscle and respiratory tissues were examined. The scientists also investigated resistance to muscle fatigue in mutant mice. They were put to sleep and using electrical stimulation, the dynamics of muscle contractions were observed and the occurrence of muscle fatigue was monitored.
It turned out that in mutant mice, compared with ordinary ones, endurance increased by 30 percent. Separate tests showed that during the day they ran, on average, 12 percent faster and 20 percent farther than normal animals. The muscles on the hind legs of the mutant mice were about twice as resistant to muscle fatigue as in normal mice. It also turned out that in the muscle tissue of the flounder muscle and diaphragm muscles of mutant animals, 10 to 50 percent more oxygen is used than in the tissue of ordinary mice.
According to the authors of the article, their results indicate that a mutation in the CMAH gene affected the ability of skeletal muscles to use oxygen more efficiently. This probably led to the development of the endurance of ancient people and their ability to run long distances.
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