What octopus and human brains have in common

If we go far enough back in , we encounter the last known common ancestor of humans and cephalopods: a primitive wormlike animal with minimal intelligence and simple eyespots. Later, the animal kingdom can be divided into two groups of organisms—those with backbones and those without. While vertebrates, particularly primates and other mammals, went on to develop large and complex brains with diverse cognitive abilities, invertebrates did not. With one exception: the cephalopods.

Scientists have long wondered why such a complex nervous system was only able to develop in these mollusks. Now, an international team led by researchers from the Max Delbrück Center and Dartmouth College in the United States has put forth a possible reason. In a paper published in Science Advances, they explain that possess a massively expanded repertoire of microRNAs (miRNAs) in their —reflecting similar developments that occurred in vertebrates.

Octopuses have complex “camera” eyes, as seen here in a juvenile animal. Credit: Nir Friedman

Octopuses have both a central brain and a peripheral nervous system – one that is capable of acting independently. Credit: Nir Friedman

Cephalopods playing with microRNAs (yellow): microRNAs may be linked to the emergence of complex brains in cephalopods. Credit: Grygoriy Zolotarov