Emergent collective motility in sea sponge cell aggregates

Sea sponges, among the earliest animals, can reassemble into functional organisms from single cells-an ancient trait that offers insight into the origins of multicellularity. When dissociated sponge cells reaggregate, the resulting clusters crawl collectively, merge on contact, and coarsen, reminiscent of a phase separation process. We track their motion and find that larger aggregates move more persistently, with mean squared displacement increasing with size. We also show that aggregates adapt their trajectories to environmental cues, coupling morphology and motility. These results reveal how cell-cell interactions and decision making generate emergent, coordinated motion, providing a physical framework for the evolution of organized multicellular life.