Deep inside the tiny brain of an ant no bigger than a grain of rice, scientists have discovered something remarkable: the roots of good parenting.
A team of researchers working with clonal raider ants found that these insects evolved caregiving not by growing entirely new brain circuits, but by repurposing ancient neural systems that once regulated hunger. The discovery, published in the journal Nature, reveals how evolution often works by borrowing and adapting existing tools rather than inventing things from scratch.
The researchers focused on two brain-signaling molecules that act like opposing regulators of ant behavior. Neuropeptide F (NPF) pushes ants toward caring for their young, while Allatostatin A (AstA) encourages them to leave the larvae behind and head out to forage for food. Young ants naturally have more NPF and less AstA in key brain regions, which keeps them focused on nursing duties inside the nest. As ants age, the balance shifts in the opposite direction, prompting the transition to foraging roles.
The team, led by Daniel Kronauer at Rockefeller University's Laboratory of Social Evolution and Behavior, identified 70 neuropeptides in total — the complete chemical signaling toolkit of the ant brain. To map how these molecules influence behavior, they developed a system that paired individual ants with individual larvae and tracked hundreds of caregiving interactions automatically.
To test whether caregiving truly remained linked to ancient feeding circuits, the researchers compared well-fed ants with starving ones. The results were striking: hungry ants showed increased NPF and reduced AstA, causing them to behave like caregivers even when no larvae were present. Once fed, the balance reversed and the ants shifted back to foraging priorities.
The findings suggest that the neural systems controlling caregiving in ants are still closely connected to the circuits that once regulated hunger — a bridge between ancient feeding behaviors and the evolution of nurturing.
Because ants and mammals share related brain signaling systems involved in caregiving, and because these behaviors naturally change as ants age, the research could help scientists better understand how parenting evolved in mammals — including humans. The ant brain, with just 60,000 cells compared to roughly 100 million in a mouse, offers a simpler model for studying these mechanisms in detail.
"Our work is a prime example of how evolution seldom invents things from scratch," Kronauer said. "Evolution takes what it has and works with that, sometimes in very surprising ways."