The New York Times reports:

The human microbiome — the trillions of microbes that live in our guts — was a stable ecosystem for tens of thousands of years before rapidly changing in industrialized countries, raising possible health concerns for modern people, scientists reported on Wednesday.

In a study of Africans and South Americans, researchers identified more than 600 species of bacteria that may once have been common in the gut but are now rare or missing entirely from people in most societies today.

Many of these microbes may have benefited people’s health, said Justin Sonnenburg, a microbiome scientist at Stanford University and an author of the new study, published in Nature.

The changing microbiome, he speculated, may have helped increase some disorders that are common in the industrialized world, from allergies to dementia.

“How bad could this be, the fact that we changed our microbiomes so much?” Dr. Sonnenburg said. “This study, I think, points to the fact that it could be pretty bad.” [Continue reading…]