I For One Welcome Our Microbial Overlords

Can the bacteria in our bodies control our behavior in the same way a puppetmaster pulls the strings of a marionette? I tremble to report that this wonderfully creepy possibility may be true.

The human body is, to some extent, just a luxury cruise liner for microbes. They board the SS Homo sapiens when we're born and settle into their assigned quarters–the skin, the tongue, the nostrils, the throat, the stomach, the genitals, the gut–and then we carry them wherever we go. Some of microbes...