ABSTRACT
If you hatch out a clutch of baby chicks and then pull a wooden model of a flying hawk over their heads they will crouch down against the ground and emit cries of alarm. This is an ancient defensive response, and it is innate. Moreover, one can raise generations of chicks without ever exposing them to a hawk-real or wooden-without extinguishing the response. The moment you display the hawk to members of the seventh or eighth generation, say, they cringe. An archetypal system, once it has evolved as a characteristic of a given species, breeds true as long as the species exists, and does not disappear with disuse.
