I’ve always wondered how eyes evolved.
You need an optic nerve to transmit the info to the brain, but why would we evolve eyes without that, or an optic nerve without eyes. What purpose would it serve?
Maybe a random mutation led to eyes that were useless till then a nerve evolved like a million years later?
Or they both happened at the same time over a million years or so?
In: Biology
Well, before there was optics that wouldn’t have been the optic nerve, but yes the nerve was there.
Eyes started as photosensitive cells, no pictures, no definition, just a cell that can sense if there is UV and heat or not. Very simple. Add more cells that can do this and you can tell better which direction that light and warmth is coming from. Create a cavity or “socket” for these cells and they can tell with even more detail where the light is coming from or if something is blocking it, perhaps even detect movement based on the blocking of that light.
Something that would count as “sight” as we think of it took a long time to come along. But there were always nerves present for all of these precursor steps. At what point did that become what we would call an “optic nerve”? that’s probably impossible to say.
It’s like the ole “what came first the chicken or the egg”? Well there were eggs first, but the things hatching out of those eggs weren’t chickens. What was the very first egg out of which something we would call a chicken emerged, therefore making it a “chicken egg”? Well that’s impossible to pinpoint.
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