Single-Celled Stentor Learns Without Brain Using Ancient Molecular Machinery

In the still water of a pond, a creature smaller than a grain of sand has quietly challenged one of science's oldest assumptions about the mind. Researchers at UC San Francisco have discovered that Stentor coeruleus — a single-celled organism with no brain, no neurons, no nervous system — learns through the same molecular machinery found in human brain cells, modifying existing proteins through calcium signaling rather than building new ones. The finding suggests that learning is not a gift bestowed by evolution upon complex nervous systems, but something far older and more elemental — a capac