So, yes. Total fairytale. As actually studying the archeological record indicates most societies we can genotype did the exact opposite for a good 60,000 years, or so. The records we have for how societies arranged themselves is painfully anorexic, although it's still enough to know that judeo-christian social constructs are just that. Constructs. And fairly modern ones. We hairless beach apes are adaptable bastards. We've built hundreds of civilizations, many with polar opposite rules and standards of behavior / culture. The genographic record is pretty clear, however; we have a rich and varied genome, and it's far more common for siblings not to share parents, than the other way around. Which means however the society organized itself? If monogamous relationships were prized? It was serial monogamy. Like modern marry & divorce & remarry cultures.
Are there differences between men & women? Absolutely.
Vive la différence. Some are biological, some are cultural.
Going against ones on culture is a difficult thing to do. I came of age in a culture which is extremely relaxed and open about sex. That's where I did the majority of my f*cking around. Living here, in the US? Pfft. Neither sanctimonious puritanical & libertine offshoot groups really appeal. But it's the culture I live in, at present. So I cope as best I can.
You say you were a feminist once who believed women could...
I'm not a feminist, at least no more than 'the radical belief that women are people'. I don't think that women can do everything men can, nor do I believe that men can do everything women can. AND the inverse; just because A man can do something, doesn't mean all men can -or even have the inclination- to do something, nor that just because A woman can do something that all women can. Are there differences between the sexes? For sure.
But individuals always vary.
I am a woman who has done most of what you once believed women could do, and now believe no women can do. I am not alone. Hardly the majority, but not some special little snowflake, either. I don't speak for all women. I don't give a damn about empowerment or any other "go sister go" kind of cause. I only speak for myself. I've done what I've done not to further the advancement of women, but because those decisions were right for me, at the time, and I was lucky enough to be able to choose them. As a person... They suited me right down to the ground.
When we get down to brass tacks it doesn't really matter to me if women in Tibet have multiple husbands, women in Tehran can't share a cab with a man who isn't their husband, women in the _______tribe (modern day, mind blanking, will look up) function as the rulers, while the old men raise the grand babies (What IS it about old men & little kids? They do both seem to have the same kind if joyful heart.), and the parents do neither the ruling nor raising as our culture's parents do, much less what the Etruscans or Lascaux or Xia, or Jōmon, or any other peoples did ... If I'm living in the US in 2016, want 1 husband, but am taking a cab with 2 men I don't know, to go raise my own child. I'm hardly alone, though. Both historically and presently. I'm not doing anything new or special. My life is my own. If I'm lucky, it's what I want to make of it.
Black and white, though, this world isn't.