For a long time, scientists believed that spiders and scorpions evolved from ancient marine arthropods living on land. However, a recent study has shed new light on their origins, suggesting that their brains may have originated in the ocean.
Researchers have re-examined a 500-million-year-old fossil of Mollisonia symmetrica, a now-extinct marine arthropod from the Cambrian period. The study’s author, neurophysiologist Nicholas Strausfeld, notes that this fossil has a brain organization similar to that of modern arachnids.
Unlike other Cambrian fossils with a “front-to-back” arrangement, Mollisonia displays a linear brain structure, which may indicate high-speed leg movements and complex prey-chasing behaviors. The finding is considered exceptional, but more research is needed to confirm its implications.
While the study’s results are promising, it highlights the complexities involved in studying fossil brains and nervous systems. Further investigation is necessary to understand the true origins of spiders and scorpions.
Source: https://www.npr.org/2025/07/25/1256217296/spider-ocean-origin-fossil-ancestors