A single celled organism that can clump together with its own kind is giving scientists a fresh glimpse into the earliest moments of animal evolution. The microbe, a relative of the choanoflagellates, does not just stick to surfaces. It actively aggregates, forming temporary multicellular groups. That behavior, researchers say, may mirror the ancient step that led to the first animals.
A microbe that chooses company over solitude
The organism was collected from marine sediments near the coast of Spain. Researchers at the Institute of Evolutionary Biology in Barcelona and their collaborators identified it as a previously unknown species of choanoflagellate, a group of unicellular eukaryotes considered the closest living relatives of animals. Unlike many choanoflagellates that live alone or form simple colonies by failing to separate after cell division, this one uses a different strategy. It gathers cells together through active adhesion, a process that requires energy and specific molecular signals.
How sticking together changes the game
When food is scarce, the cells begin to clump. They do not fuse into a single body. Instead, they hold onto each other using proteins on their surfaces, forming loose, reversible clusters. The researchers observed that the clusters can break apart and reform, suggesting a flexible system of cell to cell recognition. This kind of aggregative multicellularity is rare among choanoflagellates and has not been seen before in this lineage. The finding suggests that the genetic toolkit for sticking together may have existed long before true multicellular animals evolved.
Why this matters for understanding our own origins
For local biologists in Spain, the discovery adds a new piece to the puzzle of how life made the leap from single cells to complex bodies. The choanoflagellate was found in a region already known for rich microbial diversity, and its behavior offers a concrete example of how simple cell adhesion could have evolved. The study, published in Nature, shows that the genes involved in this aggregation are similar to those used by animals for cell communication and tissue formation. That genetic overlap strengthens the idea that the ancestors of animals were capable of temporary cooperation long before they became permanently multicellular.
This single celled relative does not prove that animals evolved from aggregating microbes. But it does show that the ability to clump together on demand is older and more widespread than previously known. The clusters form, dissolve, and form again, a quiet reminder that the line between alone and together is not always clear.
