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Maybe this seems basic but it constantly blows my mind. Why does nearly everything have:

* two eyes on head above the mouth and smelling organ(s) (antennae "smelling organs")
* the brain is in the head

Basically, nearly all vertebrates & a shocking number of invertebrates have a head with a brain in it and a "face"

Does this imply a common ancestor with a head with a face & two eyes? OR is this convergent?

(We know that complex eyes are convergent, but did this start with simple eyes?)