Everything that we’ve learned about the gut microbiota challenges traditional scientific beliefs, which is one reason why it has become a topic of so much interest and controversy, both in the world of science and the media. It is also the reason why some people are posing deeper, more philosophical questions about the impact of the microbiome: Are our human bodies just a vehicle for the microbes living in it? Do the microbes manipulate our brains to make us seek out foods that are best for them? Should the fact that we humans are outnumbered by nonhuman cells change our concept of the human self?While such philosophical speculations are fascinating, the implications of what the science of the human microbiome has revealed so far in the last decade are equally profound. Just as the Copernican Revolution in the sixteenth century fundamentally changed our understanding of the world’s position in the solar system, and Darwin’s revolutionary theory of evolution proposed in the nineteenth century has forever changed our position within the animal kingdom, the human microbiome science is forcing us again to r …