Arthritis causes pain and suffering for millions of people around the world, but it's also the byproduct of an evolutionary mutation that allowed early humans to make the move from Africa to colder climates tens of thousands of years ago. Researchers at Stanford University have discovered that a genetic variation made humans shorter and more compact as a means of protecting them against frostbite in the colder temperatures of northern climates, Newsweek reports. In addition, their limbs got shorter, making them less vulnerable to breaking if people should, say, slip on ice. The downside of this evolutionary adaptation was an increase in the likelihood of osteoarthritis.
The Stanford study, published Monday in Nature Genetics, shows how a variation in the GDF5 gene became more prevalent in humans moving out of Africa into colder climates 50,000 to 100,000 years ago. This variation doubles the chances of developing painful joint problems while also reducing height by about 0.4 inches on average, the Telegraph reports. And since arthritis generally doesn't develop until after the age of reproduction, the gene mutation was passed on from generation to generation. The Stanford researchers discovered that the genetic variation causing this increase in arthritis is common among Europeans but rare in African populations. (A Canadian woman's arthritis may qualify her for euthanasia.)