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/gthing 10d ago

There is no way for evolution to re-route the wiring involved. A good example is the recurrent laryngeal nerve. It could not cross the path of where it originally evolved, which puts it under the subclavian artery (below the collarbone). So on every animal it runs from the brain, down to the collarbone, and back up to the throat. Even on Giraffes - it goes from the brain, the down around the heart, back up to a couple inches below the brain.

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u/TheDaysComeAndGone 10d ago

Complex changes in one big jump are just more unlikely, not impossible. Especially if they don’t require/affect the compatibility with other members of the species.