On Sunday, Kenyan distance runner Eliud Kipchoge broke the world marathon record by 78 seconds, racing across a Berlin course in just 2:01:39. As Vernon Loeb notes for The Atlantic, this time translates to “26 straight, blazingly fast, 4-minute and 38-second miles.”
Kipchoge may be in a class of his own, but a new study published in Proceedings of the Royal Academy B suggests that all humans share an innate propensity for long-distance running. These findings, based on research led by University of California San Diego cellular and molecular physician Ajit Varki, trace physical endurance to the cellular level, pinpointing a genetic mutation as one of the key factors in early hominids’ transition from forest dwellers to speedy, upright predators roaming the dry African savannah.
Popular Science’s Jillian Mock reports that the study focuses on the CMP-Neu5Ac Hydroxylase, or CMAH, gene, which mutated roughly two to three million years ago—around the same time hominids underwent a shift in lifestyle from non-human primate behavior to actions more in line with contemporary humans. As Kashmira Gander writes for Newsweek, this change was accompanied by physical adaptations, including the development of larger feet, stronger gluteal muscles, and longer legs.
Kashmira explains: “Early hominids could run for longer distances and until the point of exhaustion—known as persistence hunting—all while coping with the sun's heat, while other animals snoozed.”
Today, animals ranging from cows to chimpanzees and mice carry a functional CMAH gene, which aids in the production of a sugar molecule called sialic acid. These mammals can make two types of acid, but as Elizabeth Pennisi writes for Science magazine, humans’ CMAH gene is “broken,” leaving them unable to produce more than one type of acid.
Previous studies have linked humans’ mutated CMAH gene to severe degenerative muscular dystrophy as well as increased risks of cancer and type two diabetes, but Varki and his colleagues argue that its ramifications aren’t completely negative. In fact, CMAH may be the driving force behind long-distance running, a seemingly singularly human trait.
To test their hypothesis, the researchers recruited two groups of mice. One contained animals with functioning CMAH genes, while the other consisted of mice with doctored “broken” genes. According to Discover’s Mark Barna, when the team prompted the mice to run on miniature treadmills, the group without functioning CMAH exhibited 30 percent better endurance than their CMAH-equipped counterparts. They also ran, on average, 12 percent faster and 20 percent farther.
Following the treadmill tests, co-author Ellen Breen, a physiologist at UCSD, analyzed the mice’s muscles and determined that those carrying the mutated gene were more resistant to fatigue. Popular Science’s Mock adds that the same animals tended to process oxygen more efficiently.
“It is reasonable to speculate that this mutation may have been essential for running faster and further,” the authors conclude in their study.
Still, additional research is necessary to cement the connection between CMAH and human endurance. University of Massachusetts biological anthropologist Jason Kamilar, who was not involved with the research, tells Science’s Pennisi that “mice are not humans or primates. The genetic mechanisms in mice may not necessarily translate to humans or other primates.”
In an interview with Popular Science, University of California Riverside biologist Ted Garland adds that it’s too soon to call the mutation “essential” in the evolution of long-distance running.
“If this mutation had never happened, likely some other mutation would have happened,” he notes.