This Genetic Mutation May Have Helped Ancient Humans Survive the Ice Age
Here's a riddle for anthropologists and geneticists alike: What do breastfeeding, shovel-shaped teeth, and the last Ice Age have in common? The answer is EDAR, a gene that made a major impact on the ancestors of Native Americans and East Asian peoples about 20,000 years ago.
It's riddle that's only been solved recently, but the implications are fascinating.
During the last Ice Age, humans living in northern latitudes struggled to get enough vitamin D due to lower exposure to ultraviolet light—like today, parts of the Arctic Circle and surrounding areas wouldn't see sunlight for months at a time. Vitamin D deficiency can lead to a weaker immune system, fatigue, and other illnesses, but the lack of vitamin D hits babies especially hard—because they're almost wholly dependent on breastfeeding, they need to get all their vitamin D from their mothers.
This is where EDAR comes in.
A new study led by Leslea Hlusko, a Professor at University of California, Berkeley, found that some Native American and East Asian populations mutated, resulting in mothers with "increased mammary ductal branching," which allows for more vitamin D and fat to reach the baby during breastfeeding. At the same time, EDAR causes a distinct change in the shape of the incisors, making them more shovel-shaped.
According to Hlusko:
"People have long thought that this shoveling pattern is so strong that there must have been evolutionary selection favoring the trait, but why would there be such strong selection on the shape of your incisors? When you have shared genetic effects across the body, selection for one trait will result in everything else going along for the ride."
This wasn't a niche adaptation, either—when Hlusko looked at the archaeological record, she found that 100 percent of Native Americans had shoveled teeth before the arrival of European colonists, suggesting that the breastfeeding adaptation appeared as well. If this is true, then it's yet another example of humans evolving to match the changing conditions of our planet, like the deep-diving Bajau people of East Asia.