Current Biology (2026). DOI: 10.1016/j.cub.2026.03.080"> Graphical abstract. Credit: Current Biology (2026). DOI: 10.1016/j.cub.2026.03.080

Scientists have known for more than a century that a single-celled organism with no nerve cells—much less a brain—can behave in ways that resemble learning. But those observations only went so far. How the organism did that was a mystery.

Now, scientists at UC San Francisco can explain how this simple organism, called Stentor coeruleus, learns: It uses molecular machinery that resembles what neurons have in the human brain. The results suggest that learning may be a fundamental feature of life.

In findings published in Current Biology , the researchers used modern neuroscience tools to study the pond-dwelling "Stentor," which is shaped like a trumpet and is large enough to be seen with the naked eye.…