Evolution mostly involves small, gradual changes, and for good reason – we might expect that large changes to an animal’s genetic code, and therefore to its body plan, simply wouldn’t work. It would be like shoving an extra cog into a finely-tuned machine and expecting it to fit in – the more likely outcome is a malfunctioning mess.

But that’s not always the case, at least not for the evolution of the human eye. New research shows that the eye and its connections to the brain are surprisingly flexible, and can incorporate major evolutionary changes with ease.

In our retinas, cone cells are responsible for giving us colour vision. Most mammals have just two types, one that is sensitive to short