The Evolutionary Function of Sleep: Why Your Brain Needs Downtime

Imagine a gazelle on the savannah. It lies down, closes its eyes, and disconnects from the world for hours. It looks suicidal. Lions are prowling, yet the animal enters a state of total vulnerability. Evolution usually ruthlessly eliminates such risks. The fact that it hasn't brings us to the evolutionary function of sleep.

This paper proposes the "Computational Necessity Hypothesis". The author argues that sleep is not just about physical rest; it is the price we pay for being smart. Our brains are not like filing cabinets with separate drawers for different memories. Instead, they are "non-modular" networks where everything overlaps. If you learn a new skill, you change connections that might also support an old skill.

The evolutionary function of sleep and catastrophic interference

This overlap creates a danger called "catastrophic interference". If you kept tweaking your brain's connections while awake and processing the world, you might accidentally overwrite your ability to walk while learning to dance. The study suggests that the brain cannot fix this whilst online.

Therefore, the author proposes that sleep provides a necessary "offline" state. By shutting down sensory input, the brain can safely traverse its own network. It searches for a "system-wide equilibrium". It optimises the whole structure so new and old memories can coexist. If this hypothesis holds true, we don't sleep just to rest. We sleep to stop our minds from crashing.