A recent study by Ruibao Li and Jennah Dharamshi published in Nature may help us understand the beginnings of animal evolution billions of years ago. These findings are the result of a collaboration between researchers at Indiana University Bloomington, the Institute of Evolutionary Biology in Spain and Uppsala University in Sweden, and was led by J. P. Gerdt and Iñaki Ruiz-Trillo.
These researchers found that after feeding a specific bacteria to a certain unicellular relative of animals, the single cells began to stick to one another, revealing a possible mode by which our ancestors began to evolve into animals billions of years ago.
Animal bodies are made up of trillions of cells that stick together and cooperate. Billions of years ago — before animals evolved — every living thing on earth was a single-celled organism. Eventually some of these cells began sticking together, working together and then reproducing as multicellular organisms. Some of these early multicellular organisms evolved into present-day plants or fungi, while others evolved into animals.
How the cells began to stick together and why they did so has long been a mystery to scientists. To get to the bottom of this enigma, Li and his colleagues studied Ministeria vibrans , a unicellular organism that shares ancient ancestors with present-day animals.
M. vibrans survives by eating bacteria. Li rigorously tested different bacterial foods until he found one that encouraged single M. vibrans cells to stick together and become multicellular. The bacteria got trapped between the aggregating cells, meaning that it was more efficient for M. vibrans to collect food by sticking together rather than remaining as single-celled organisms. Further, by sticking together, the cells might be able to protect their food from other organisms.
Sticking together also provides opportunities for cells to exchange genes via mating, which may produce new genetic combinations that enable adaptation to new environments.
Li and Dharamshi observed that when M. vibrans evolved from unicellular to multicellular, it produced the same proteins that many animal cells use to stick together. The multicellular form of M. vibrans also produced many proteins that animal cells use to communicate and coordinate behavior. The team concluded that the unicellular organisms that evolved into animals also likely used these proteins to form multicellular bodies and cooperate.
Li and his colleagues are excited to uncover further insights from the aggregation behavior of M. vibrans . Because the organism is much simpler than humans, it is easier to study, meaning it could even help reveal overlooked genes involved in certain developmental processes or diseases.
However, “What this organism is most powered to answer is what the unicellular ancestor of animals was like,” said J. P. Gerdt, associate professor of chemistry at Indiana University Bloomington. “It’s one of the best systems we have to go back a billion years to see what our ancestors were like at that stage.”
Nature
Observational study
Cells
A unicellular relative links aggregative multicellularity to animal origins
9-Jun-2026