|By Joseph Scalise | 3 years ago|
A special genetic mutation in the ancestors of Native Americans may have enabled nursing mothers to pass more nutrients along to their infants, helping them survive in regions that receive little to no sunlight.
This new research — which comes from scientists at University of California, Berkeley — shows how populations that lived in the far north resisted health problems like rickets. To do that, the team studied ancient teeth from many native groups and found that a unique gene likely boosted the development of milk ducts within women’s breasts and allowed them to raise healthier children.
“Teeth telling us something about fertility? That’s really amazing,” said Julienne Rutherford, an anthropologist at the University of Illinois in Chicago who was not involved in the study, according to Science.
The gene — known as EDAR — is linked to thicker hair shafts, more sweat glands, and shovel-shaped incisors. As a result, any fossils with such teeth likely had the mutation. Both Native Americans and Asians carry a version of the gene today. Though researchers are not sure how it spread throughout the world, they do know that it was so helpful that it moved to almost every population in the Americas.
Scientists came to that conclusion by looking at teeth from more than 5000 people from 54 archaeological sites across Europe, Asia, and the Americas. That revealed that most of the specimens had shoveled teeth, suggesting roughly 40 percent of the individuals in Asia and all of the 3183 fossils of Native Americans analyzed in the study had the mutation. It is likely that the some members of the first group to arrive in Beringia probably carried the gene as well.
The spread of the mutation makes sense because higher latitudes typically put nursing infants at risk. With less sunlight, children cannot get enough vitamin D in their skin and often succumb to serious health problems. Though adults can eat meat rich in vitamin D to compensate, babies cannot.
By developing their own EDAR variant, the populations who called the north home likely produced more mike and delivered more nutrients through the liquid. That would have then made those with the gene more likely to survive and helped it spread throughout different regions.
While more research needs to be done to see how an increase in breast ducts might deliver more nutrients, the team is confident in their research. They plan to further their study of the gene and see how certain variants might affect both breast development and density.
“This is not just a Native American story,” lead author Leslea Hlusko, a researcher at the University of California, Berkeley. “Everyone with shovel-shaped incisors has this gene that may compensate for vitamin D deficiency.”
These new findings are outlined in the Proceedings of the National Academy of Sciences.