Breakthrough study reveals that human and octopus brains have common features

A common feature that connects humans and octopuses has only recently been revealed. It may sound a little bit quirky to you, but not to scientists.

Published very recently in Science Advances today, a team led by Nikolaus Rajewsky of the Max Delbrück Center has now shown that their evolution is linked to a dramatic expansion of their microRNA repertoire.

As said in the statement, the last known common ancestor of humans and cephalopods is a rudimentary wormlike animal with low intelligence and basic eyespots, which can be found if we travel far enough back in evolutionary history.

Invertebrates did not develop vast and sophisticated brains with different cognitive capacities, as did vertebrates, particularly primates and other mammals. The cephalopods are the sole exception.

"This is what connects us to the octopus!"

According to Professor Nikolaus Rajewsky, Scientific Director of the Berlin Institute for Medical Systems Biology of the Max Delbrück Center, the study's findings might mean miRNAs play a crucial role in developing complex brains. "This is what connects us to the octopus!" says Rajewsky.

These cephalopods are known to engage in significant RNA editing, which means they frequently use certain enzymes that can recode their RNA. This made Rajewsky wonder if octopuses had any other RNA tricks up their sleeves in addition to being skilled editors.

The largest microRNA families in the animal world

“This is the third-largest expansion of microRNA families in the animal world and the largest outside of vertebrates,” says lead author Grygoriy Zolotarov, MD, a Ukrainian scientist who interned in Rajewsky’s lab at MDC-BIMSB while finishing medical school in Prague.

“To give you an idea of the scale, oysters, which are also mollusks, have acquired just five new microRNA families since the last ancestors they shared with octopuses – while the octopuses have acquired 90!”

Octopuses are the only invertebrate species that are unmatched in terms of evolution. They possess core neural and peripheral nervous systems, the latter capable of operating independently. Even if an octopus loses a tentacle, the remaining tentacle is still mobile and touch-sensitive.

The fact that octopuses utilize their arms so consciously, like tools to open shells, may be why they are the only animals to have evolved such complex brain functions. Additionally, octopuses exhibit additional traits of intelligence, like curiosity and memory. They can identify persons and even favor some over others. Since their color and skin structure vary while they sleep, researchers now think that they even dream.