Ok, let's explain the eye. Let's agree that there needs to be a stepwise process; From something stupidly simple, to something profoundly complex. It has to be stepwise, it can't just be "well, light sensitive cells exist, and a inverted curved lensed organ is better" because goddamn it, you need to go from 'a' to 'B C D E F' before you get to 'G'.

So let's do that.

I know Richard Dawkins is an ass, but here he is as a much younger self explaining just that, long before he became a jaded asshat filled with malice.

If you hate that, here's a modern TED explanation, but Dawkins honestly does a better job.

It all starts with light sensitive cells.

Unsurprising, and not just because it's a thing that exists, but photons interact with electron distribution across complex molecules and a protein whose confirmation is altered slightly by photon interaction is going to be a regular occurrence and all it takes is one which is very sensitive to this effect to imagine basic utility arising from it. Photosynthesis is based on protein interaction with light and it's a few small step from light = food to light = an eye.

These light sensitive proteins fire off I'm getting close to food, and when they aren't, I'm moving away from food. Why? Well I don't know that, but it's true. I don't know that more light means easier photosynthesis, which is good for me because I photosynthesize (or maybe because I eat photosynthesizes)

So next I group these proteins in strategic locations - more light towards my front, less light in my back, now I understand direction

And then I curve it inward so I can identify precise direction

Then it curves so much that it starts to close in on itself, which ought to be terrible, but actually I'm getting closer and closer to a pin hole lens

But now I have this cavity and I want to keep gunk from getting in so I close it off with a transparent cover

But covers don't have to be uniform, oops, mine has different thicknesses at different parts -- actually, one version of that is a lens, wow that's awesome.

But that lens is only good for one direction. Oh well, I'll just use these structural cells to hold it precisely in place... oh wait, what it those structural cells flex and alter the shape of my lens, now I can focus at distance.

Oh my, I have an eye.

Ok, let's explain the eye. Let's agree that there needs to be a stepwise process; From something stupidly simple, to something profoundly complex. It has to be stepwise, it can't just be "well, light sensitive cells exist, and a inverted curved lensed organ is better" because goddamn it, you need to go from 'a' to 'B C D E F' before you get to 'G'.

So let's do that.

I know Richard Dawkins is an ass, but here he is as a much younger self explaining just that, long before he became a jaded asshat filled with malice.

If you hate that, here's a modern TED explanation, but Dawkins honestly does a better job.

It all starts with light sensitive cells.

Unsurprising, and not just because it's a thing that exists, but photons interact with electron distribution across complex molecules and a protein whose confirmation is altered slightly by photon interaction is going to be a regular occurrence and all it takes is one which is very sensitive to this effect to imagine basic utility arising from it. Photosynthesis is based on protein interaction with light and it's a few small step from light = food to light = an eye.

These light sensitive proteins fire off I'm getting close to food, and when they aren't, I'm moving away from food. Why? Well I don't know that, but it's true. I don't know that more light means easier photosynthesis, which is good for me because I photosynthesize (or maybe because I eat photosynthesizes)

So next I group these proteins in strategic locations - more light towards my front, less light in my back, now I understand direction

And then I curve it inward so I can identify precise direction

Then it curves so much that it starts to close in on itself, which ought to be terrible, but actually I'm getting closer and closer to a pin hole lens

But now I have this cavity and I want to keep gunk from getting in so I close it off with a transparent cover

But covers don't have to be uniform, oops, mine has different thicknesses at different parts -- actually, one version of that is a lens, wow that's awesome.

Oh my, I have an eye.