Scientists have just discovered that the beneficial microbes in our guts have been passed down for millions of years. The bacteria evolved alongside humans and hosted in our original ancestors. The findings are in a study recently published in the journal Science.
Beneficial bacteria live in human hosts and affect us in many ways. Some of these bacteria help our immune system, others aid in food digestion, and some even assist in vitamin synthesis. There is also research that suggests gut microbes can change moods and a healthy mix of beneficial bacteria can help with depression. We inherit most of our microbes from our mothers during birth, while others are picked up from our environment and interactions with other people.
Researchers analyzed stool samples from bonobos, chimpanzees, and gorillas. These African apes are some of our closest relatives. The team also collected samples from people living in the state of Connecticut. The researchers found that humans share most of our gut microbes with the studied apes. Using gene sequencing, the scientists were able to construct evolutionary trees for the major groups of bacteria present in human and ape guts. They discovered that the bacteria had coevolved with humans. As the common ancestor of humans and apes began to diverge into separate species, the bacteria also had an evolutionary event. During human evolution, the bacteria split into strains unique to each primate host. Two major bacteria groups, Bacteriodaceae and Bifidobacteriaceae, didn’t change much after humans had evolved. Another group, Lachnospiraceae, switched between several host species. The researchers speculate that this is due to that bacteria family’s ability to produce spores, allowing them to easily change hosts.
Gut microbes may have been more important in evolution than previously believed. As they evolved alongside humans, they changed our biology in many ways. These beneficial bacteria played large roles in immune system and digestive processes, possibly changing the course of human evolution.
Andrew H. Moeller et al. Cospeciation of gut microbiota with hominids. Science (2016).