Single gene loss may have made humans long- distance runners

Loss of gene triggered key changes — from fertility rates to cancer risk

Los Angeles, Sept. 12: The functional loss of a single gene may have helped humans become one of the best long- distance runners in the animal kingdom, a study has found.

Researchers at the University of California San Diego in the US studied mice engineered to lack the gene called CMAH.

Two to three million years ago, the functional loss of CMAH triggered significant changes in what would eventually become the modern human species, altering everything from fertility rates to increasing cancer risk from eating red meat, researchers said.

The study, published in the journal Proceedings of the Royal Society B, suggests that the lost gene may have contributed to humanity's well- documented claim to be among the best long- distance runners in the animal kingdom.

At roughly the same time as the CMAH mutation took hold, human ancestors were transitioning

from forest dwellers to life primarily upon the arid savannahs of Africa.

While they were already walking upright, the bodies and abilities of these early hominids were evolving dramatically, researchers said.

Major changes in skeletal biomechanics and physiology resulted in long, springy legs, big feet, powerful gluteal muscles and an expansive system of sweat glands able to dissipate heat much more effectively than other larger mammals, they said.

Such changes, scientists say, helped fuel the emergence of the human ability to run long distances relatively tirelessly.

This allowed our ancestors to hunt in the heat of the day when other carnivores were resting and to pursue prey to their point of exhaustion, a technique called persistence hunting, they said.

“We discovered this first clear genetic difference between humans and our closest living evolutionary relatives, the chimpanzees, more than 20 years ago,” said Ajit Varki, a professor at UC San Diego School of Medicine.

Researchers investigated how the genetic difference might have contributed to the origin of Homo, the genus that includes modern homo sapiens.

“We evaluated the exercise capacity ( of mice lacking the CMAH gene), and noted an increased performance during treadmill testing,” said graduate student Jon Okerblom.