The article discusses the evolution of the vertebrate gut microbiota, comparing it with other microbial communities. It highlights that the human gut microbiota is typical for an omnivorous primate but is highly differentiated from free-living communities. The Human Microbiome Project should include a broad range of humans and other mammals to explore the evolutionary history of the biosphere. The study shows that diet, host morphology, and phylogeny influence the composition of the gut microbiota. The human gut microbiota is more similar to other primates than to non-primates, with diet playing a key role in clustering. The gut microbiota of primates and mammals is influenced by their diet and lifestyle. The study also shows that the gut microbiota of herbivores and omnivores differ, with herbivores having more specialized microbiotas. The gut microbiota of mammals is influenced by their diet and the environment, with different habitats leading to different microbial communities. The study also shows that the gut microbiota of different mammals is influenced by their phylogeny and diet. The article concludes that the gut microbiota of vertebrates is distinct from free-living communities and that the Human Microbiome Project should include a broad range of samples to understand the evolutionary history of the biosphere.The article discusses the evolution of the vertebrate gut microbiota, comparing it with other microbial communities. It highlights that the human gut microbiota is typical for an omnivorous primate but is highly differentiated from free-living communities. The Human Microbiome Project should include a broad range of humans and other mammals to explore the evolutionary history of the biosphere. The study shows that diet, host morphology, and phylogeny influence the composition of the gut microbiota. The human gut microbiota is more similar to other primates than to non-primates, with diet playing a key role in clustering. The gut microbiota of primates and mammals is influenced by their diet and lifestyle. The study also shows that the gut microbiota of herbivores and omnivores differ, with herbivores having more specialized microbiotas. The gut microbiota of mammals is influenced by their diet and the environment, with different habitats leading to different microbial communities. The study also shows that the gut microbiota of different mammals is influenced by their phylogeny and diet. The article concludes that the gut microbiota of vertebrates is distinct from free-living communities and that the Human Microbiome Project should include a broad range of samples to understand the evolutionary history of the biosphere.