Science reports:

Deep in the human gut, myriad “good” bacteria and other microbes help us digest our food, as well as keep us healthy by affecting our immune, metabolic, and nervous systems. Some of these humble microbial assistants have been in our guts since before humans became human—certain gut microbes are found in almost all primates, suggesting they first colonized a common ancestor. But humans have also lost many of these helpers found in other primates and may be losing even more as people around the world continue to flock to cities, a researcher reported last week at a microbiology meeting in Washington, D.C. Those absent gut microbes could affect human health, he says.

“This work helps us develop a new understanding of the course of human biological and cultural development,” says Lev Tsypin, a microbiology graduate student at the California Institute of Technology who was not involved in the new study.

The microbiome comprises all the bacteria, fungi, viruses, and other microscopic life that inhabit an individual, be it a person, a plant, or a planaria. For humans and many other species, the best characterized microbiome centers on the bacteria in the gut. The more microbiologists study these gut microbes, the more they link the bacteria to functions of their hosts. In humans, for example, gut bacteria influence how the immune system responds to pathogens and allergens, or interact with the brain, affecting mood. [Continue reading…]