In their past work comparing primate gut microbiomes, Moeller and colleagues simply looked at genetic markers that broadly identified what genera of bacteria or other microbes were present. Moeller has now taken a closer look at exactly what microbial species have gone missing from the human gut by trying to compile the full genomes of current gut microbes in our closest relatives. “You can tell what went extinct [in humans] by looking at what’s in other primates,” Moeller says.