How did eye lense evolve?

Submitted by TheSonOfKayra t3_125nk1x in askscience

As far as I know, very special conditions are required for such a formation to occur in nature. At this point, how did the lens in the eye take its current shape? What were the factors causing this?

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Stacksmchenry t1_je54o5m wrote

There is a fantastic visualization of this on the show Cosmos (the Neil Degrasse Tyson version) on the evolution episode (how molecules work was the name of the episode if I recall)

Sorry I can't give you a great scientific answer but if you're looking for a surface level explanation it should help.

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Klijntje88 t1_je5l7i2 wrote

This is a great response, it's beautifully visualised which makes it easy to understand

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ronnyhugo t1_je6p4hn wrote

The eye actually evolved four separate occasions (at least). Because at every point in making an eye, you gain an advantage. And that is how the lens also evolves.

IIRC the book "Selfish Gene" goes into this. Great audio book that's worth listening to a few times.

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Riptide360 t1_je5exgw wrote

Your species relationship with food dictates a lot about how your eyes evolved.

In many land animals who eat primarily with their faces in their food they have an inner eye lid tied to the jaw muscle that closes during eating to keep food debris out. You can see the vestige of ours in the pink muscle stub in the inner corner of your eye and compare it to the full version found in your dog, cat or bird.

The placement of your eyes is also related to what you eat. Herbivore animals often have horizontal pupils, their day predator animals often have circular pupils and their night predator animals will frequently have vertical pupils. https://physicsworld.com/a/eye-shape-reveals-whether-animal-is-predator-or-prey/

In humans our ability to see in color was in part due to our evolution with gauging the effort to eat ripe fruit. This also improved our fore arms as more than legs and improved our hand eye coordination and thumb evolution.

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bigfatfurrytexan t1_je59134 wrote

Something to keep in mind: in the creatures eyes began evolving in, you aren't talking about generations spanning 20 years or something. Generations were on the order of a few weeks, and evolution was rather rapid fire by comparison to today. We have a nice stable planet, with stable weather and stable chemistry. When life was evolving basic forms of biology, that was not quite the case.

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Beyond that, there is more than 1 path to creating an eye.

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bigfatfurrytexan t1_je598e1 wrote

It really is a matter of photoreceptor cells that evolved in a pit rather than flat on the surface. The "pit" allowed for a directional sensation.

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screen317 t1_je93pgl wrote

> and evolution was rather rapid fire by comparison to today

Important to note that we are in the middle of a mass extinction period.

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E_Kristalin t1_jebzpwt wrote

After the extinction period is over, a lot of unfilled niche means an possible explosion of new species, but not during the extinction period.

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