Consider hiccups. These spasms in our diaphragms are triggered by electric signals generated in the brain stem, which we inherited from amphibian ancestors who emit similar signals to control their gills. Hiccups are the same phenomenon as gill breathing.

Our inner fish extends beyond physicality. New research reveals that many fish display a wide range of surprisingly sophisticated social behaviors, pursuing interpersonal, interfishal relationships that seem almost embarrassingly familiar.

“Fish have some of the most complex social systems known,” Michael Taborsky, a behavioral ecologist at the University of Bern in Switzerland, said. “You see fish helping each other. You see cooperation and forms of reciprocity.”