Oyewumi--separating from the biological

Do people with biological differences naturally interact in a separated manner? For example, in the Yoruba society that Oyewumi describes, where gender is supposedly absent from hierarchy or social structure, did women approach men with their biological differences in mind? Is it natural for us to be weary of people who are biologically different, whether it be race, gender, sexual orientation, etc.? Can social categories be singularly defined (i.e. can one category have significance without another)? Is it really possible that "gender, being a social construction, is also a historical and cultural phenomenon. Consequently it is logical to assume that in some societies, gender construction need not have existed at all" (10)? I mean, don't you think the first humans looked at each other, and were like, "okay, our bodies are different, we have different strengths and weaknesses and biological functions. This will affect how we interact."...? Sorry if this is sort of abstract, I guess I'm just trying to understand Oyewumi's hope for a completely non-gendered society...