The point the book makes is that as we transferred from foraging to farming the entire dynamic shifted. As hunter-gatherers there was not competition for resour

The point the book makes is that as we transferred from foraging to farming the entire dynamic shifted. As hunter-gatherers there was not competition for resources and it didn't matter who the genetic father of a child was. In most foraging societies today people don't care about paternity and treat all the children in the village as their own. In several Amazonian tribes they believe that children are made from an accumulation of semen in the mother and husbands often offer their wives to other people in the village. The shift to farming meant that population density increased and competition for goods meant that wealth began to concentrate. With that there was a reason to ensure paternity. So yes we made a shift, but looking at our existence for the majority of the time that we've existed as a species we can see why we have always had a very tough time with monogamy. Also, the idea that women have little desire to have multiple husbands is not true at all. Women are just as promiscuous as men are and when given the freedom are more than willing. Again, I highly recommend Sex at Dawn because the views that you're expressing are the exact ones that it addresses point by point.