3.1 Why do we have a brain?

Why do we have a brain? According to Daniel Wolpert — a neuroscientist at Columbia University — this is the first question to ask if we want to understand how brains work. And his answer may not be what you expect: the earliest brains on Earth don’t seem to have evolved for reasoning or reflection, but in a context where being able to move deliberately was a matter of survival.

But let’s go step by step.

There was a time when no animal could move on its own — a time before brains had evolved.

Imagine travelling back around 600 million years, to the Ediacaran period, and diving into ancient ocean floors. You’d see something similar to what’s pictured on the panel in front of you: a landscape of animals nothing like those we know today — organisms anchored to the seabed, creatures we would mistake for plants. And just like plants, these animals could not move on their own.

Now jump forward in time to the Cambrian period, beginning around 540 million years ago. You’d find yourself in a dramatically transformed world — you can see it on the screen in the centre of the panel. Many animals no longer sit still: they swim, dig, chase, and flee.

It’s in the Cambrian that the first brains appear — likely as an evolutionary solution for gathering information from the outside world and turning it into fast, coordinated decisions.

As Daniel Wolpert writes:

“We have a brain for one reason, and one reason only: to produce adaptable and complex movement.”