A single gene mutation that helped early humans survive in Europe and Asia during the Ice Age may also increase the risk of arthritis in modern-day humans.
Researchers from the Stanford University School of Medicine and Harvard University have found a gene mutation that helped our ancestors survive colder temperatures by “coding” for shorter limbs, according to new research published in the journal Nature Genetics.
As modern humans migrated out of Africa between 50,000 and 100,000 years ago during the last Ice age, they were faced with colder temperatures. A genetic variant for shorter limbs may have helped them better withstand frostbite, the researchers argue. Shorter bones also meant there was less chance of breaking a bone if they slipped on ice.
There’s a downside, however. The gene in question, known as GDF5, which is involved in bone growth and joint formation, also increases one's risk of osteoarthritis – a condition that causes joints to become painful and stiff. In humans, mutations in the GDF5 gene have been shown to be linked to a 1.2 to 1.8 times increase in the risk of osteoarthritis.
Of course, the prospect of painful joints is not a pretty one, nor particularly useful if you’re hunting mammoths in Ice Age Europe. However, the risk from cold temperatures may have outweighed the risk of osteoarthritis, which usually occurs after prime reproductive years. The gene was repeatedly favored as early humans migrated out of Africa and moved into colder corners of the world. It’s thought that at least half of Europeans and Asians have the gene variant, yet it remains relatively rare in African populations.
“Because it’s been positively selected, this gene variant is present in billions of people,” David Kingsley, professor of developmental biology at Stanford, said in a statement. “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."
Armed with this fresh insight, Professor Kingsley believes their study could have practical implications in the world of medicine.
"This is an incredibly prevalent, and ancient, variant. Many people think of osteoarthritis as a kind of wear-and-tear disease, but there’s clearly a genetic component at work here as well," he added. "Now we’ve shown that positive evolutionary selection has given rise to one of the most common height variants and arthritis risk factors known in human populations.”