C.G. Jung on Archetypes and Adaptation

"Archetypes are systems of readiness for action, and at the same time images and emotions. They are inherited with the brain structure - indeed they are its psychic aspect. They represent, on the one hand, a very strong instinctive conservatism, while on the other hand they are the most effective means conceivable of instinctive adaptation. They are thus, essentially, the cthonic portion of the psyche...that portion through which the psyche is attached to nature."

C.G. Jung (1921) Psychological Types, The Collected Works of C.G. Jung, Vol. 6, par. 684, Princeton, NJ: Bollingen - Princeton University Press