Female Orgasm Remains an Evolutionary Mystery

 If female orgasm is evolutionarily connected to male, opposite-sex twins should have similar orgasmic function.

But that’s not what they found. Instead, while orgasmic function was genetically shared in same-sex twins — brother tended to share function with brother, or sister with sister — the relationship vanished in opposite-sex twins, though both share the same amount of genetic material. The underlying genetics, and thus the underlying evolutionary pressures, thus appear to differ.

http://www.wired.com/wiredscience/2011/09/female-orgasm/