The microscopic mites that live on our faces and in our hair are providing scientists with some interesting insight on human evolution. After collecting samples from around the world, scientists discovered different human populations have different mites that essentially follow families through generations.
"It's shocking that we're only just discovering how deeply our histories are shared with the mites on our bodies," Dr. Michelle Trautwein, senior author of the study and a curator of entomology at the California Academy of Sciences, said in a news release. "They aren't just bugs on our faces, they are storytellers. Mites tell us about our own ancient history. It's a complex story, and we've only just scratched the surface."
While face mites (Demodex folliculorum) are passed down through generations, they are not casually transferred between humans. For the study, researchers analyzed the mitochondrial DNA of different mites in order to link them to human evolution. To do this, 70 human hosts were sampled from around the world.
"We discovered that people from different parts of the world host different mite lineages," Trautwein continued. "The continent where a person's ancestry originated tended to predict the types of mites on their faces. We found that mite lineages can persist in hosts for generations. Even if you move to a faraway region, your mites stick with you."
For example, African Americans that have been living in the U.S. for generations still have African mites. This suggests some mite populations are better able to survive and reproduce on hosts from certain geographic regions, and supports the "Out of Africa" hypothesis, which states "every living human today is descended from a group that evolved in Africa and dispersed into the wider world."
D. folliculorum mites are actually tiny arachnids that live in human hair and consume skin cells and oils. For most people, mites are harmless. However, the microscopic animals are known to cause various skin or eye disorders, such as rosacea, a condition that causes redness and small red facial bumps.
"Another exciting mite revelation from our work is that mites aren't shared easily," Trautwein added in the academy's release. "Mites are not casually transferred to passersby on the street. We seem to share mites primarily with our family, so it likely takes very close physical contact to transmit mites."
The findings were recently published in the Proceedings of the National Academy of Sciences.
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