Even though humans today need not hunt for their food or chase their prey, being able to run long-distance and maintain stamina is a part of our genetic makeup. This ability is believed to be responsible for the success of the human race in terms of conquering territory and eventually dominating the planet. A new study conducted on mice has suggested how losing a gene has helped humans run the distance.
This change occurred two to three million years ago when the functional loss of a gene (CMAH) lead to the evolution of the modern human species. Clues about this discovery first came through 20 years ago, when Ajit Varki, a physician-scientist at the University of California San Diego (UCSD), and his colleagues found one of the initial differences between humans and chimpanzees. It was a gene called CMP-Neu5Ac Hydroxylase aka CMAH. It was discovered that humans possess a broken version of CMAH, while other primates have it. This gene helps build a sugar molecule called sialic acid which sits on the cellular surfaces, as humans lack the gene, they do not produce this sugar.
Two decades later, Ajit Varki and team, evaluated the exercise capacity of a group of mice that did not have the CMAH gene, comparing the results to a group of mice that did. When the mice were prompted to run on miniature treadmills, it was observed that the mice without the functioning CMAH showed 30% better endurance than the group that had functioning CMAH. These mice also ran 12% faster and 20% further, on average, as compared to their counterparts during the exercise. Ellen Breen, another researcher, added the observation that the mice without the CMAH exhibited increased mitochondrial respiration and hind-limb muscle with more capillaries increasing the oxygen and blood supply, as well as greater resistance to fatigue. Andrew Best, a biological anthropology graduate student at UMass in Amherst, believes that similar improvements through evolution probably benefitted our human ancestors.
The loss of CMAH gene and sialic acid has also been linked to the enhancement of innate-immunity in early hominids by researchers, as well as improving the long-distance running ability. Conversely, researchers have also mentioned that certain sialic acids may lead to an increased risk of type 2 diabetes, trigger inflammation and contribute to an elevated risk of cancer due to the consumption of red meat.