It's no secret that microbes living in our guts play an important part in our overall health, and now new research show that apes - humans' closest relative - have better, more diverse gut bacteria than we do.
"It took millions of years, since humans and chimpanzees split from a common ancestor, to become 60 percent different in these colonies living in our digestive systems," Howard Ochman, professor of integrative biology at The University of Texas at Austin and co-author of the study, said in a press release.
"On the other hand, in apparently only hundreds of years - and possibly a lot fewer - people in the United States lost a great deal of diversity in the bacteria living in their gut."
In fact, those of us living in the United States have gut microbes that are 70 percent different than chimps'.
Researchers worry that this might translate into negative health effects for Americans. For instance, a lack of a varied microflora has been linked to asthma, colon cancer and autoimmune disease, as well as depression and mental illness, Discovery News notes.
Scientists behind this latest study analyzed fecal samples from humans, chimps, bonobos and gorillas to discover our intestinal differences.
As for why Americans evolved to have less diversity in their gut microbiomes is up for speculation, but one possibility is that our insides shifted to cope with our meatier, less plant-based diets.
Furthermore, why did our gut microbes change so quickly - over a matter of hundreds, rather than millions, of years? Some researchers suggest that we spend more time indoors, use antibacterial cleansers and rely too much on antibiotics (which kill gut flora).
"Declining diversity in the gut has been a trend for a long time," said Ochman. "It's tantalizing to think that the decrease in microbial diversity in humans is due only to modern medical practices and other lifestyle changes, but this research shows other factors over time also must have played a role."
The study was published in the journal Proceedings of the National Academy of Sciences.