One half billion years ago, before Pangaea, the early Cambrian epoch started.
In 30 million years, there was a huge explosion of life. Most of the current phyla, types of life, we have today, evolved in that period. This is called the Cambrian Explosion.
(This image is an Early Cambrian period reef community, taken from this page about the Early Cambrian. It’s from Rachel Wood’s The Ecological Evolution of Reefs, and I just love the quality of the the image. Diagrammatic and illustrative.)
There’s one theory, that’s put forward in a book called In the Blink of an Eye, and first brought to my attention by Matt Jones, that says this explosion was due to a big arms race, due to the evolution of the first eye.
The proto oceans of early Earth were dirty, and slowly they cleared. At a certain point, animals moved through them to find different chemical concentrations, towards more carbon or whatever. All detection was local. It was all done with the surface of the body.
But when the oceans cleared of dust, light could penetrate. And when light could penetrate, animals could perceive information from further away than they could reach. Suddenly new abilities were needed… moving quickly, camouflage, deduction, object tracking, expectations. Mainly: better eyes, better senses!
Unfortunately, people who do actual science from that era, a chap named Simon Conway Morris in particular, have fairly conclusively said this theory is bunk. Oh well. It doesn’t matter.
The point is…