I have often been asked where the archetype comes from and whether it is acquired or not. This question cannot be answered directly. Archetypes are, by definition, factors and motifs that arrange the psychic elements into certain images, characterized as archetypal, but in such a way that they can be recognized only from the effects they produce. They exist preconsciously, and presumably they form the structural dominants of the psyche in general. They may be compared to the invisible presence of the crystal lattice in a saturated solution. As a priori conditioning factors they represent a special, psychological instance of the biological "pattern of behaviour," which gives all living organisms their specific qualities. Just as the manifestations of this biological ground plan may change in the course of development, so also can those of the archetype. Empirically considered, however, the archetype did not ever come into existence as a phenomenon of organic life, but entered into the picture with life itself.
— Carl Gustav Jung
The crystal lattice image is doing something careful here. Jung is not saying the archetype is a thing — a stored form, a template waiting to be stamped. He is saying it is a condition of arrangement, invisible until something crystallizes around it. You never see the lattice; you see what the saturated solution does when the lattice is present. That distinction protects against two common errors: the error of treating archetypes as contents to be catalogued ("the hero," "the great mother," listed and filed), and the error of treating them as causes in the mechanical sense — as if psyche were a machine with interchangeable parts.
The deeper implication is that the archetype is not older than life, it is coextensive with it. It entered with life itself. This means asking where it came from is like asking where metabolism came from — the question dissolves into the question of what living is. What Jung is tracking is not a mythology or a cultural deposit but a biological-psychological reality so prior to experience that experience is only possible within its structures. The dream does not illustrate an archetype; the dream is where the archetype becomes legible, briefly, before the solution goes saturated again and the lattice returns to invisibility.
Carl Gustav Jung·Psychology and Religion: West and East·1958