“Arthritis is the price for our ancestors surviving the Ice Age, say scientists,” reads a Telegraph headline. Newsweek adds, “Human evolution: Africa exodus made homo sapiens shorter and gave them arthritis.”
Both articles respond to research published recently in Nature Genetics, in which U.S. and Canadian scholars reveal that a variation of a particular gene, GDF5, increases chances of developing arthritis and makes people shorter on the one hand, but carries evolutionary advantages on the other. The latter includes helping our ancestors better protect themselves against frostbite and mitigate bone damage after slipping on ice.
“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,” the Stanford story noted. “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.” And yet, the gene variant, relatively rare in Africans, is present in at least half of Europeans and Asians.
“Because it’s been positively selected, this gene variant is present in billions of people,” Dr. Kingsley said. “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.”
“For the 10 million Britons suffering from arthritis, it may be cold comfort to know that they might not be alive today at all, were it not for their aching limbs,” observes the Telegraph article.
According to Dr. Kingsley, history here would carry not only academic interest, but could also impact medicine today. “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 said. “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.”
But Newsweek quotes a Johns Hopkins professor, Christopher Ruff, who questions some of the findings, however much he found them “fascinating and provocative.”
The first “anatomically-modern humans” outside Africa, who were found in the Middle East and then in Europe and East Asia, were very tall, and height declined only some 20,000 years later, according to Dr. Ruff. “While the gene coding for shorter stature may have been present in these populations, it certainly wasn’t selected for until much later,” he told the magazine.
He added that Europeans today are among the world’s tallest, which appears to respond to optimal living conditions, but nonetheless suggests that there is genetic potential for increased height. And modern African populations vary widely in height. “Some of this is doubtless due to environmental conditions, but it also suggests other genetic factors at work,” he says. “So, I think the evolutionary basis of stature variation is likely to be quite complex.”