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Humans have domesticated themselves, and it appears we have thus changed the ecosystem on our very flesh, according to a new study by biologists from the University of Waterloo.

The microbiome on the skin of humans has much less diversity than that of other mammals who do not live in homes or scrub with soap, according to the paper, in The Proceedings of the National Academy of Sciences.

“Human skin microbial communities were distinct and significantly less diverse than all other sampled mammalian orders,” the scientists said. “To our knowledge, this study represents the largest existing mammalian skin microbiome survey. Our findings demonstrate that human skin is distinct, not only from other primates, but from all 10 mammalian orders sampled.”

Skin swab samples were collected from the backs, torsos and inner thighs of 38 species, ranging from zoos to farms to households, and to the wild.

The group included lions, horses, rhinos, reindeer, dogs and housecats, among other species.

The swabs were amplified with PCR and then sequenced on an Illumina machine.

Those results were compared and contrasted with previous data from 20 humans, using an identical method.

Taking all the samples together, a random forest modeling technique distinguished between humans and animals with a 98.5 percent accuracy rate.

“Within nonhuman sample, host taxonomic order was the most significant factor influencing skin microbiota, followed by the geographic location of the habitat,” the researchers said. “Given the recent evolutionary divergence of humans as distinct species form other nonhuman primates, these results suggest that modern human practices, such as living within a built environment, wearing clothing and washing with soap, have strongly impacted the diversity and composition of the skin microbiota that can be sampled with sterile swabs.”

Previous studies have shown, however, that a return to nature may mean a wider array within the flora on our skins, the scientists said.

“A study of previously uncontacted Amerindians demonstrated that changes in lifestyle, such as living outdoors, resulted in higher diversity, lending further support to this finding that modern human practices may be rapidly changing the skin microbiota,” the Waterloo team explained.

 

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