The kind of early human social structure that encouraged sexual promiscuity was a delicate thing. It required a small tightly-knit group of less than 150 individuals, an abundant natural food supply, and an inability to hoard resources. As I look out my front door in New York City, I don't detect much potential for the establishment of that kind of social order. It's strictly big boxes of bananas, all the way up Columbus Avenue.
Yet the popular buzz in the book's first month seems to miss all of this. "We're really meant to be promiscuous!" yell the headlines.
No. The reality is more sobering. The material conditions that would permit a stable culture of sexual promiscuity are long since gone.
From the same article (linked above).
The social conditions may be different for most people, but the basic biology (our bodies) isn't so much different at all. Our bodies are the same, essentially, as the bodies of our Pleistocene ancestors.
Humans During the Pleistocene: