How aggression evolves: when neural circuits are repurposed

How do entirely new behaviors emerge in evolution?

In a new study published in Nature, researchers from our research groups 'Neural Information Flow' and 'Genetics of Behavior' show how predatory aggression evolved in nematodes through changes in neuromodulatory circuits rather than the addition of new neurons.

By comparing the peaceful bacterivore Caenorhabditis elegans with its predatory relative Pristionchus pacificus, the team combined machine learning, genetics, and neurobiology to dissect aggressive behavior into distinct behavioral states. They found that two opposing neuromodulators, octopamine and tyramine, act as a push-and-pull system that determines whether the worm remains passive or enters a predatory mode.

Crucially, the study reveals that evolution repurposed existing sensory circuits by redirecting neuromodulatory signals. This functional rewiring enabled the emergence of a new hunting strategy without increasing the number of neurons.

Read the full press release here.