Poissons,grenouilles, femmes et hommes: The appropriation and retention of archetypal systems for reproduction

In contradistinction to other biological systems, the reproductive mechanisms in sexually reproducing species are unique in that their success relies upon a synchronous interaction between two separate individuals. Reproduction has become increasingly more efficient as higher forms have developed internal fertilization and gestation. Although our anthropomorphic perspective has dominated the understanding of reproductive processes, ‘recent discoveries’ make it clear that this reproductive efficiency has been gained by retention of previously present biological mechanisms whose origins are in the vestigial excretory tracts and ducts which are the precursors of the reproductive tract. We refer to these as ‘archetypal systems’. They include the interaction between sex steroid sensitive tissues and sex steroids, the renin-angiotensin system and the macrophage/monokine response to infection. Through these mechanisms the reproductive tracts have maintained control over the microenvironment in which the reproductive processes occur. Thus, gamete development in male and female, and fertilization and early embryonic existence in the female tract prior to implantation still occur in compartments which are extracorporeal, i.e., separated from blood or subendothelial spaces, and are controlled by cellular mechanisms found in ancient excretory tracts. Since the majority of the changes between lower forms and contemporary mammals are anatomical modifications which have favoured the success of these extracorporeal events within the developing, generally land-based mammals, we should take special note of lower animals, understanding the evolutionary appropriation of mechanisms designed to furnish the suitable microenvironment from the surrounding tissues. Our ability to integrate these into a meaningful approach to the control of reproduction and to the diagnosis and treatment of reproductive disorders will be much enhanced if we are able to break intellectual barriers and view reproduction from the perspective of those lower forms to which we owe so much of our present reproductive efficiency.