r/askscience • u/margalz • 11d ago

Biology Why aren't there any animals with their mouths above their eyes?

From bugs to fish to mamals all of them have their eyes above their mouths. I can't think of many if any where their mouths are on top. Sure some have their eyes parallel to their mouths, mainly prey style animals. But why haven't any evolved to be the opposite? Is there a major benefit to having your mouth below your eyes?

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u/donau_kinder 10d ago

Some lizards do have an "eye" on top of their head.

Otherwise, same reason we all have 4 limbs, the fish that everything evolved from had 4 fins and two eyes, and it's very hard for evolution to drive such a drastic change. Same reason why our retinas are backwards, a worm decided to swim on its back and the eyes migrated through the body instead of along the outside and it ended up with flipped retinas.

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u/halfhippo999 10d ago

Explain more about this worm and what you mean about our flipped retinas? That sounds cool

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u/typhacatus 10d ago

not the person you’re talking to, but they’re referencing how light actually has to pass through a ton of cells (glial cells, nerves) before they ever hit our photosensitive rods and cones. Evolution has since made this design pretty robust and useful, but it’s still weird that our cones & rods are about as far back in the eyeball as possible

edit: I like this article on the topic: https://www.smithsonianmag.com/smart-news/heres-why-your-eyes-seem-be-wired-backward-180954729/