A single gene mutation in humans which resulted in the functional loss of a gene is now believed to be responsible for a series of vastly important changes in human evolution. According to new research, this change may have enabled ancient humans to evolve and and become more like modern humans.
A new paper published on Sep. 12 in the journal Proceedings of the Royal Society B suggests that humans lack the same gene as mice called CMAH. The analysis and results suggest that the same gene mutation contributed to what humanity is today, allowing us to be among the best long-distance runners on Earth.
The research also suggests that the CMAH mutation took place when ancient humans were changing their lifestyle from that of forest dwellers to one of life in the African savannas. Scientists believe that at that time, humans were already walking upright. They also believe that the abilities of early humans were evolving at a dramatic rate, leading to drastic changes in their skeletal construction and physiology which resulted in long legs, big feet and powerful muscles which enabled them to run.
According to scientists, that single gene mutation in humans enabled them to walk long distances without getting exhausted. Early humans seemed to find a lot of advantages in this ability, like hunting even in the scorching heat of the day at times when other carnivores were resting.
Dr. Ajit Varki, senior author on the paper, is a professor of medicine and cellular and molecular medicine at the University of California, San Diego School of Medicine and co-director of the UC San Diego Salk Center for Academic Research and Training in Anthropogeny. He explained that they’ve been studying this gene mutation for more than two decades.
“We discovered this first clear genetic difference between humans and our closest living evolutionary relatives, the chimpanzees, more than 20 years ago,” Varki said in a statement.
Scientists estimated an approximate time of when this single gene mutation took place and documented the impact of this change on the fertility of a mouse model with the same mutation. Varki and colleague Pascal Gagnmeux, Ph.D., professor of anthropology and pathology, started investigating whether this genetic difference also resulted in the origin of Homo, the advanced human which include Homo Sapiens, and the extinct species Homo habilis and Homo erectus.
“Since the mice were also more prone to muscle dystrophy, I had a hunch that there was a connection to the increased long distance running and endurance of Homo,” said Varki, “but I had no expertise on the issue and could not convince anyone in my lab to organize this long-shot experiment.”
To learn whether the genes in question are compatible, graduate student Jon Okerblom built running wheels for a mouse and borrowed a mouse treadmill.
“We evaluated the exercise capacity (of mice lacking the CMAH gene), and noted an increased performance during treadmill testing and after 15 days of voluntary wheel running,” said Okerblom, the study’s first author.
Scientists say that after the CMAH gene mutated in the Homo species about 2 million to 3 million years ago, it altered the way hominids and modern humans used sialic acids, or the sugar molecules protecting the surfaces of animal cells. They are vital contact points in how other cells interact with the surrounding environment. They believe the gene mutation in humans enhanced their natural immunity but also caused sialic acids to be a biomarker for cancer risk.
“They are a double-edged sword,” said Varki. “The consequence of a single lost gene and a small molecular change that appears to have profoundly altered human biology and abilities going back to our origins.”
