When monkeys are brought into captivity, they lose the bacterial diversity of their native micriobiome. As researchers from the University of Minnesota recently found, the gut bacteria of captive monkeys resemble those of humans.

Scientists sequenced the DNA of bacteria collected from the guts of two monkey species, the highly endangered red-shanked douc and the mantled howler monkey. Researchers analyzed the microbiomes of both wild and captive specimens.

Among both species, captive specimens featured gut bacteria much less diverse and very similar to the microbial communities found in human intestines.

Researchers identified the same pattern in several zoos on three different continents.

"We don't know for certain that these new modern human microbes are bad, but on the other hand many studies are now showing that we evolved together with our resident microbes," Dan Knights, a computer science and engineering professor at Minnesota, explained in a news release. "If that is the case, then it is likely not beneficial to swap them out for a totally different set."

The research also showed that microbiomes among individual wild monkeys are more distinct, while those of captive monkeys are more uniform.

Scientists also tested the gut bacteria among a population of semi-captive red-shanked doucs living in a large sanctuary. The results revealed microbiomes roughly halfway between the microbiota signatures of captive and wild doucs.

The diet of the semi-captive monkeys more closely resembles the diet of wild doucs, suggesting a loss of plant diversity in the diet of captive monkeys may be responsible for the transformed microbiome.

Stool samples showed fiber from plants accounts for as much as 40 percent of the diet of wild monkeys, while captive monkeys featured no traces of plant fiber.

"We think this study underscores the link between fiber-rich diets and gut microbiome diversity," Knights said.

The new research was published in the journal PNAS.