Widespread extinctions of co-diversified gut bacterial symbionts from humans

Humans and other primates harbour complex gut bacterial communities that influence health and disease, but the evolutionary histories of these symbioses remain unclear due to a lack of information about the state of the microbiota in ancestral primates. Here we show that hundreds of gut bacterial lineages co-diversified with primate species over millions of years, but that nearly half of these ancestral symbionts have been lost from humans. Analyses of thousands of metagenome-assembled genomes from humans, chimpanzees, bonobos, and other non-human primates revealed significant co-diversification within ten gut bacterial phyla. Remarkably, 44% of the co-diversifying clades detected in African apes were absent from available human metagenomic data. In contrast, only ~3% of the clades displaying the weakest evidence for co-diversification and detected in African apes were absent from humans. This study identifies bacterial symbioses that predate hominid diversification, revealing accelerated extinctions of ancestral, co-diversifying symbionts from human populations.