This article uses and imaginary, 3-way dialogue in which D. Kriegman and D. Schwartz respond to each other's views of sex and gender identity as representatives of their respective Darwinian and postmodern (Queer Theory) theoretical positions. Both positions radically challenge conventional psychoanalytic models of the role of early developmental experience. Yet their perspectives clash sharply over which kinds of sex and gender expression are most violated by existing analytic theory, as well in terms of their views of the power of reproductive functions to influence the experience of sex and gender. A broader evolutionary model is presented in which human sex and gender identity are seen as shaped by multiple, contradictory, evolutionary selection pressures. This alternative evolutionary model stresses the negotiation of identity within the family and the vital adaptive functions of gender multiplicity.