[Inge_CAV]

"Interesting, all the societies he cites seem to stuck in the stone age."

Of course, they are too busy screwing each others brains out to advance beyond the stone age. : )

[Dimensio]

Well the article doesn't predict that they should be out of the stone age. The article does not claim that promiscuity is good for societial advancement, only for perpetuation (and perhaps proliferation) of the species.