For some time now I’ve been bewitched by the microbiome–those 100 trillion passengers that make our bodies their vessel (here’s a piece from the New York Times last year, and a long essay from last month). But I was especially intrigued by a paper that came out today in Nature. Scientists found they could sort people into just three distinct gut microbiomes, much like they can sort people into four blood types. Here’s my story in the Times, which will appear in tomorrow’s edition.

One thing that you won’t find in the article is some intriguing speculation I indulged in with the scientists I interviewed. Researchers have clearly demonstrated that microbes can influence their host’s behavior. They release