We are what we eat, and so are our microbiomes. A new study shows that alterations in diet, along with other environmental factors, had a major impact on gut biomes over time as animals were domesticated. In a process that closely tracks changes in the human diet since industrialization, this shift had implications on the health of domesticated animals — and possibly on humans as well.
The question that challenged human evolutionary biologist Rachel Carmody was one of nature vs. nurture. Her study “Effects of domestication on the gut microbiota parallel those of human industrialization,” published today in eLife, answered it definitively.
“Evidence in humans and many animals to this point suggests that, surprisingly, genetics plays a small role compared to environmental influences,” said Carmody, an assistant professor in the Department of Human Evolutionary Biology and principal investigator of the department’s Nutritional and Microbial Ecology Lab.
Carmody and Aspen Reese, a junior fellow in her lab, looked at nine different pairs of wild animals and their domesticated descendants, such as wolves and dogs, wild boars and pigs, and wild European rabbits alongside the domestic variety. Though the pairs differed profoundly from one another, the tame counterparts have encountered many common environmental changes during domestication, including shifts in population density, physical activity, patterns of reproduction, medical interventions such as exposure to antibiotics, and human contact.
In addition, “We’ve changed their diets,” said Carmody. “For example, many domesticated animals are eating foods originally cultivated for human use, in processed forms that are relatively easily digestible, and that tend to be richer in fat.” While the microbiomes of wild and domesticated animal pairs resembled one another, “The process of domestication shifted the divergent microbiomes of these different species in a common direction. In other words, we were able to detect a global signature of domestication,” she said.
The fact that environment rather than genetics drove that shift became apparent as researchers switched a single environmental variable between wild and domesticated pairs — feeding wolves dog chow, for example, and raw meat to dogs. “We used diet as one example of an environmental factor that we know has changed with domestication and with industrialization in profound ways,” Carmody said.