If trying to model reallife human biological gender, then humans probably evolved as paleolithic nomadic clans that resemble bonobos.
Generally, bonobos are peaceful, highly sexual, and egalitarian. Bonobos use casual sex for social bonding and resolution of conflict. Bonobos are bisexual. (Are there any studies to see if minority individuals have a preferred orientation?) There is no awareness of the connection between sex and pregnancy, so culturally the bonobos have mothers but no fathers. So children are loyal to their mothers. In this way, when the female group decides in an egalitarian way, the male group being loyal to their mothers tend to go along with the decisions of the female group.
In paleolithic human gender division, there are probably males who self-identified with the female group (care-givers and gatherers), and females who self-identify with the male group (hunters).
In the human context, I suspect individuals already exhibited strong sexual and gender diversity. So all permutations existed. Males who self-identify as male but prefer other males. Males who self-identify as female but prefer other females. And so on. Likewise, some individuals were strongly monogamous, and other individuals strongly polyamorous. And so on. Even if some individuals discovered the connection between sex and pregnancy, it was culturally insignificant. Paleolithic humans only had mothers. And were generally peaceful. Resembling bonobos.
The Neolithic Revolution introduced new, more violent, cultures, where the discovery of farming led to non-nomadic settlement, competition over farmable land, and the repurposing of hunting skills to ‘hunt’ other humans in war.
In some sense, the human shift from paleolithic peace to neolithic violence is a reallife ‘exile from the Garden of Eden’.