Some reflexes, like the rooting, sucking and grasping reflex, are theorized to exist because

Some reflexes are theorized to exist because they have the survival value. Sigmund Freud First to theorize that we pass through different stages, behaviour is governed by the reflexes that we are born with, start to develop schemata, but need to develop permanence.

the answer to this question is a

layer 3 is younger than layer 6.