To me it seems obvious that one of the primary causes of differences in end sexual conduct has its roots in the anatomical differences of men and women. While accidental and satisfying self-stimulation of the penis is for most males very easy, the commonly elusive and non-prominent positioning of the clitoris makes masturbation difficult for many females. It doesn't help that due to its auxiliary role in reproduction, in some countries it is extremely common for young women to go on completely oblivious to the existence of the clitoris. Hence the ultimate development of male and female sexuality diverges widely. Cultural evidence? The narrative of discussion of masturbation among men, adolescents, and even young boys is extremely vibrant. The narrative on female masturbation is virtually nonexistent and in most cases doesn't develop until post-adolescence at the earliest, and has only really blossomed in the twentieth century as a result of (well, besides the sexual revolution) development of machine-based stimulation.
There was a historical shift in beliefs.
I find this very odd. How could a major cultural lineage be wrong about something so much a part of ordinary experience?
When I say wrong, I don't necessarily mean that we're right, or the ancients were right, though there's a lot of evidence that the Victorians were wrong.
My favorite theory is that people's amount of desire for sex varies sufficiently that there's enough noise to make it easy to see patterns that aren't there. I leave the possibility open that there was a change (possibly dietary) which affected libido levels differently between men and women.
People are sufficiently punitive about sex that there's going to be lies and misdirection to support the current theory about how people are supposed to be.