I'd have to say yes sex has evolved. There are swinger clubs etc out there, whereas when our ancestors walked around, they wouldn't have thought of having an orgy as it probably never even entered their mind. Cleopatra was also know for her sexcapades as well as her beauty. Also back then, they didn't have video/TV with porn readily available to people. It would have been primitive compared to now.

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An erotic story
The instructor and student
Secretary learns how to take a dicktation
The story of sister stephanie