A single genetic change linked both to a reduction in human height and an increase in osteoarthritis risk might seem like it would quickly be kicked to the evolutionary curb. After all, how could it be an advantage to be both shorter and less mobile in the cutthroat competition for scarce resources and fickle mates? Darwin’s finches would be appalled.
Now, researchers at the Stanford University School of Medicine and at Harvard University have shown that, despite its association with the painful joint disease, this genetic variant was repeatedly favored as humans migrated out of Africa and into colder northern climates. At least half of Europeans and Asians harbor the gene variant, which is relatively rare in African populations.
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“Because it’s been positively selected, this gene variant is present in billions of people,” said David Kingsley, PhD, professor of developmental biology at Stanford. “So even though it only increases each person’s risk by less than twofold, it’s likely responsible for millions of cases of arthritis around the globe. This study highlights the intersection between evolution and medicine in really interesting ways, and could help researchers learn more about the molecular causes of arthritis.”
A more compact body structure due to shorter bones could have helped our ancestors better withstand frostbite and reduce the risk of bone fracture from falling, the researchers speculate. These advantages in dealing with chilly temperatures and icy surfaces may have outweighed the threat of osteoarthritis, which usually occurs after prime reproductive age.
Cold may have selected for gene variant
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“The gene we are studying shows strong signatures of positive selection in many human populations,” said Kingsley, who is also a Howard Hughes Medical Institute investigator and a member of Stanford Bio-X. “It’s possible that climbing around in cold environments was enough of a risk factor to select for a protective variant even if it brought along an increase likelihood of an age-related disease like arthritis, which typically doesn’t develop until late in life.”
A paper describing the research was published online July 3 in Nature Genetics. Kingsley is the senior author. Harvard graduate student Jiaxue Cao and former Stanford postdoctoral scholars Terence Capellini, PhD, and Hao Chen, PhD, share lead authorship. Capellini is now an associate professor of human evolutionary biology at Harvard, and Chen is an associate clinical scientist at Genentech Inc.
Source: https://t-tees.com
Category: WHY
