See, this is where the problem is. The evidence for polyamory (different from polygamy) would be *pre* historic. Remember that history is written by the victors (in our age- men), so women would necessarily be at the whims of men in this writing of it. What about sexual behavior before we could write about it (or, at least, recognize a language that might be writing about it?)? I think there is plenty of evidence that women were just as sexually adventurous,as men. Look at the concept of the heiros gamos, for instance, and the vagina-shaped graves of neolithic Western Europe, as well as the vast collections of extremely detailed stone vaginas.

There's also contemporary examples of female sexploration, for instance the concept of partible paternity amongst certain indigenous peoples where a child is believed to be fathered by several men, and thus promiscuity is encouraged. Then there are the bonobo monkeys- closer to us genetically than chimpanzees. Not to mention the amazing amounts of data supporting the promiscuity of both male and female insects and other animals.