An adaptive gut microbiome might have shaped human evolution

Feb. 19 (UPI) -- How did human beings end up as one of the most successful species on Earth?

New research suggests the unique nature of the human microbiome may have shaped human evolution and the dispersal of humans across the globe.

For the study, published Wednesday in the journal Frontiers in Ecology and Evolution, an interdisciplinary team of scientists compiled a range of previously published research in order to compare the microbiota among humans, apes and other non-human primates.

Their findings showed the microbes found on and inside humans are especially unique.

"Humans have strange skin microbes, strange stomachs (with consequences for gut microbes), unusual vaginal microbiomes and more," lead study author Rob Dunn, ecologist at North Carolina State University, told UPI in an email. "This was all known in disparate literatures, but becomes more conspicuous when pulled together. The evolutionary transitions that these differences imply likely had big effects on our evolution and we are only beginning to make sense of what those effects might have been."

The new research makes the case that to understand the course of human evolution, more attention must be paid to the shifting makeup of microbiomes of our ancestors.

The human microbiome isn't just unique, it's also incredibly important and influential.

"Microbiome research over the past couple decades has made it clear that these microbial communities can affect human physiology and behavior (they affect how we digest our food, how our immune and nervous systems develop, etc.)," study co-author Katherine Amato, an anthropologist at Northwestern University, told UPI in an email. "Therefore, we think there may be a link between unique human microbiomes that have contributed to unique human physiological and behavioral traits that have contributed to our evolutionary success."

As detailed in the new study, the unique adaptability of the human microbiome helped humans digest new foods and colonize novel environments.

Additionally, research suspect social sharing of microbes via close cohabitation and the sharing of fermented foods resulted in local microbial adaptations. By outsourcing their microbiota to their food, early humans were able to re-inoculate themselves and ensure the group enjoyed similar microbiomes.

"The oldest alcohol fermentation appears to be from a preagricultural site in Israel," Dunn said. "But it seems more and more likely that fermentation is far more ancient. Homo erectus had the smarts and probably the tools necessary to ferment both meat and alcohol."

At this point, the influence of the human microbiome on human evolution is largely hypothetical. But researchers hope their efforts will inspire other scientists -- including paleoanthropologists, medical researchers and ecologists -- to test their hypotheses and investigate the questions presented in their paper.

Several of the study's authors are moving on to investigate topics related to the link between the human microbiome and human evolution.

"I really want to understand the big story of the extended microbiome of hominins," Dunn said. "Even simple questions still need to be addressed. For example, what are the general rules with regard to the kinds of fermentation that are possible in tropical realms versus temperate ones?"