Researchers at the European Molecular Biology Laboratory report that something resembling a cerebral cortex exists in the marine ragworm, a small creature with ancient roots that has not changed in hundreds of millions of years.

To conduct their study, Dr. Arendt and his colleagues used a technique called cellular profiling to determine what genes were turned on and off in the cells of the ragworm’s brain. This sort of profiling provides a molecular footprint for each cell.

Remarkably, the molecular footprint in certain parts of the ragworm’s brain, known as mushroom bodies, had a very similar footprint to the cerebral cortex.