At what point did the separation of male and female occur?

[irish-deutsch.livejournal.com]

was invited by a University l.g.b. society to give a lecture on Transgender. i have accepted and intend to make reference to the evolution of Gender roles......Really intend to put forward the theory that the separation of the Genders is nurture more than nature...that evolution society developed this. I may or may not be right...but well am researching...don't claim to be an expert...that's why I'm posting here!

Any assistance from informed brains welcome!
Thanks
A