Octopuses evolved remarkably complex brains, and a chromosome rearrangement 270 million years ago may explain how | Earth

Editor’s note: This article features research done by scientists at the University of Vienna, the Marine Biological Laboratory and several other institutions.

A genome is usually pictured as a long string of genes, read from one end to the other. Inside a cell, though, that string is folded up tight, so stretches of DNA that sit far apart on the string can end up touching.

In octopuses, squid, and cuttlefish, an ancient rearrangement of the chromosomes put many distant stretches side by side. New research suggests those new contacts may have helped these animals evolve their unusually complex brains.

The researchers present that link to the brain as a proposal, not a proven result. Thea Rogers, a biologist in the Department of Neurosciences and Developmental Biology at the University of Vienna, led the work. Her team compared folded DNA in three species, mostly in embryos, and tested one stretch of that DNA directly.

“The genome isn’t just a sequence of genes. It’s folded into a complex three-dimensional structure,” said Rogers. “Understanding how that structure evolves is becoming increasingly important for understanding how new forms of biological complexity arise.”