If proximity is any indicator, man’s best friend is a creature that literally lives in our faces. Two species of facial mites live their whole lives without leaving the friendly confines of our skin pores. They hatch from eggs, crawl on eight legs, reproduce and eventually die. But while these mites are with us every day, relatively little was known about their evolutionary origins—until Associate Professor of Biology Michael Palopoli co-authored a paper that shed light on their short but fascinating lives.

“They look kind of like a cigar, with tiny little legs at one end,” Palopoli said. “They are actually tiny, microscopic. They crawl down into the pores and live there.”

Last November, Palopoli and eight co-authors, including several Bowdoin alumni who worked with him during their time at the College, published a paper outlining how face mites and the humans who host them have likely evolved together. The study attracted media attention, commanding articles in publications such as The Atlantic and Science Daily. 

Despite the popular recognition of his work, Palopoli said the increased attention doesn’t affect his research.

“It doesn’t change for me what is scientifically interesting,” he said. “I think I’ve published other results that are arguably scientifically more interesting than [these]. It’s just because it happens to be human-related that suddenly you see all this interest.”

Such interest, in part, likely stems from the fact that many people are alarmed by the idea of mites crawling on their faces. While billions of bacteria are known to live on human skin and in the body, facial mites are arachnids, members of the animal kingdom. Their closest biological relatives are spiders and ticks.

“There are males and females, so they’re obviously having sex and reproducing in or on our skin,” Palopoli said.

Still, he was quick to point out that mites don’t typically pose a health risk to their human hosts. 

“They are generally described as being commensal, which basically means they make a living on our skin but don’t do us any harm,” he said.

Palopoli began investigating mites because the species was a good laboratory example for his students. Given their relative abundance, he was surprised to discover how little research had been done about them.

When Palopoli and his team first began their research, sampling the mites did not come easily. 
“It took some trial and error,” said Palopoli. 

They ended up using a sterilized bobby pin to lift skin off of volunteers’ faces, and combing through the samples for mites. 

Once they found the mites, Palopoli and his fellow researchers isolated and analyzed their DNA. The DNA sequences revealed that, although every human subject had mites, these mites could be divided into four distinct genotypes. The distribution of these different mites was not random, but based on the continental ancestry of each human subject.  

“The people of recent European ancestry we sampled, which was a large sample...have a genetically distinct mite population from people who have ancestry from Asia, and both of them have a genetically distinct mite population from people who have ancestry from Asia, and with ancestry from Africa,” he said. 

Palopoli’s research, conducted at Bowdoin, was supplemented by researchers at North Carolina State University.

“We went ahead and sent them the information that we had so far and they added some individuals to our data set. So we published together,” he said.

Regardless of public reaction, Palopoli hopes to continue researching why different people exhibit different mite populations. One hypothesis argues that people acquire mites from their parents early in life, while another suggests that genetic differences could make some people’s faces better habitats for mites of a particular genotype.

Palopoli believes he could test these competing hypotheses by comparing the facial mite genotypes of people who were adopted to those of their parents. 

While his research may continue to focus on the evolutionary differences in mites, their presence is still something that all people have in common.

“Every reader will have mites living in their skin,” said Palopoli.