Evolution of the Mammalian Reproductive Tract and Placentation

Abstract

Phylogenetic analysis suggests that the internalization of reproduction and the development of hemochorial placentation have been accompanied by conservation of primitive genitourinary genes. The products include the renin-angiotensin system and the innate immune system. This explains what might otherwise be considered an ectopic presence of these systems in the mammalian reproductive tract and the interaction of the allograft embryo and maternal host.