A Comic Guide to the Evolution of Ancient Cells into Complex Brains

“The anus was a prerequisite for intelligence” said one biologist

By Tim Vernimmen, Maki Naro & Knowable Magazine

Comic-style group of cells with big eyes and smiles, packed together into a spherical shape. — Maki Naro

Comic section 2: Eventually, some cells evolved to specialize in cell-to-cell communication, leaving other jobs to other cells. This—or something like it—is how scientists imagine the first simple nervous systems came to be. But what’s the evidence? The oldest fossils with evidence of a nervous system date from the Cambrian period. But these nervous systems are too complicated to have been the first. Much simpler ones must have come earlier. How can we learn about those?

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Credit: Maki Naro (illustrations) and Tim Vernimmen; Inspired by “Getting Nervous: An Evolutionary Overhaul for Communication,” *Annual Review of Genetics*, 2017, and “Evolution of Animal Neural Systems,” *Annual Review of Ecology, Evolution, and Systematics*, 2017.

This article originally appeared in Knowable Magazine, an independent journalistic endeavor from Annual Reviews. Sign up for the newsletter.