One of the oldest known genetic differences between humans and chimpanzees may have helped ancient hominids, and now modern humans, succeed over long distances. To understand how the mutation works, the scientists examined the muscles of mice that had been genetically modified to carry the mutation. In rodents with the mutation, oxygen levels increased to working muscles, increasing endurance and reducing overall muscle fatigue. The researchers suggest that the mutation could work similarly in humans.
Many physiological adaptations have helped make humans stronger in long-distance running: the evolution of long legs, the ability to sweat, and the loss of fur have all contributed to increased endurance. The researchers believe they have “found the first molecular basis for these unusual changes in humans,” says medical researcher and study lead author Ajit Warki.
The CMP-Neu5 Ac Hydroxylase (CMAH for short) gene mutated in our ancestors about two or three million years ago when hominids began to leave the forest to feed and hunt in the vast savannah. This is one of the earliest genetic differences we know about modern humans and chimpanzees. Over the past 20 years, Varki and his research team have identified many genes related to running. But CMAH is the first gene that indicates a derived function and a new ability.
However, not all researchers are convinced of the role of the gene in human evolution. Biologist Ted Garland, who specializes in evolutionary physiology at UC Riverside, cautions that the connection is still “purely speculative” at this stage.
“I am very skeptical about the human side, but I have no doubt that it does something for the muscles,” says Garland.
The biologist believes that simply looking at the time sequence when this mutation arose is not enough to say that this particular gene played an important role in the evolution of running.
The CMAH mutation works by changing the surfaces of the cells that make up the human body.
“Every cell in the body is completely covered in a massive forest of sugar,” Varki says.
CMAH affects this surface by encoding sialic acid. Because of this mutation, humans have only one type of sialic acid in the sugar forest of their cells. Many other mammals, including chimpanzees, have two types of acid. This study suggests that this change in acids on the surface of cells affects the way oxygen is delivered to muscle cells in the body.
Garland thinks we can’t assume that this particular mutation was essential for humans to evolve to distance runners. In his opinion, even if this mutation did not occur, some other mutation occurred. To prove a link between CMAH and human evolution, researchers need to look at the hardiness of other animals. Understanding how our body is connected to exercise can not only help us answer questions about our past, but also find new ways to improve our health in the future. Many diseases, such as diabetes and heart disease, can be prevented through exercise.
To keep your heart and blood vessels working, the American Heart Association recommends 30 minutes of moderate activity daily. But if you’re feeling inspired and want to test your physical limits, know that biology is on your side.