Ants, wasps, bees and other social insects live in highly organized “eusocial” colonies where throngs of females forgo reproduction — usually viewed as the cornerstone of evolutionary fitness — to serve the needs of a few egg-laying queens and their offspring. How they got that way has been hard to explain despite more than 150 years of biologists’ efforts. Many researchers have thought the answer would come down to a complex suite of genetic changes that evolved in species-specific ways over a long time.

But new results suggest that a surprisingly simple hormonal mechanism — one that can be found throughout the animal kingdom — may have been enough to set eusociality in motion.

Last month, a team of researchers led by Daniel Kronauer, an evolutionary biologist at the Rockefeller University in New York, published a paper in Science that many experts are saying provides one of the most detailed molecular stories to date in the study of eusocial behavior.

The scientists found that division of reproductive labor in ants arose when an ancient insulin signaling pathway, typically involved in maintaining nutrition and growth, became responsive to social cues. In doing so, they also uncovered deeper insights into “a process underlying how the environment gets under the skin to affect behavior, physiology, and the health and well-being of other members of a society,” said Gene E. Robinson, an entomologist and the director of the Carl R. Woese Institute for Genomic Biology at the University of Illinois at Urbana-Champaign.

Kronauer and his colleagues, hoping to uncover a common origin for the ants’ evolutionary journey toward eusociality, first compared which genes were expressed differently in the brains of the queens and workers among seven diverse ant species. They found a particularly strong signal for one gene, ilp2, which codes for the ant version of insulin and was expressed consistently higher in queens. (At least two dozen other genes emerged as important as well, Kronauer noted — many of them also related to insulin production and signaling, or to brain plasticity and other traits.)

To determine the role of ilp2, the researchers focused on a single ant species, the clonal raider ants Ooceraea biroi, whose colonies lack fixed queens. Instead, the ants alternate as a group between worker and queen roles, seemingly in response to the presence of larvae: With babies around, all the adult ants stopped reproducing to take care of them.

Kronauer’s team found that insulin signaling was responsible for that cycle. Production of the hormone declined when the researchers exposed the ants to larvae, suppressing reproduction and inducing the shift to caretaking behavior. When the larvae were removed, insulin levels rose significantly — and injecting the adults with insulin caused their ovaries to reactivate even when the larvae were still around. “If you think about it, it’s a crazy but also very elegant and simple way to make an organism social, to make it responsive to larvae,” Kronauer said.

(And as Allen J. Moore, an entomologist at the University of Georgia, joked, “Anyone who’s a parent knows that your kid manipulates you.”)