The author's understanding of sex and marriage has no scientific basis and is rooted entirely on Christian beliefs, which unsurprisingly have a dim view on everything below the belt.

Studies have conclusively shown that sex and pleasure was essentially transactional in nature in prehistoric, egalitarian hunter-gatherer societies in which homosapiens lived and evolved, 90 per cent of their life on earth.

Not only is the 'monolith' of marriage, a post-agricultural, post Judeo-Christian phenomenon, the idea of 'love' and 'commitment' in marriage is even more recent.

Marriage according to the Bible was essentially a contractual transaction in which woman as property was transferred from her father to her husband in exchange for a bride-price. The status of wife as property is made clear in the last commandment.

You shall not covet your neighbours house, you shall not covet your neighbours wife, or male or female slave, or ox or donkey...ouch.

To put it mildly, agricultural civilisation and patriarchal religions like Christianity have played a huge role in perverting sex and downgrading the status of women in order to ensure social control. Ignoring these facts to idealise monogamy and is a travesty of truth.
Perhaps the author should realise that the Bible itself is a post-agricultural product and the Garden of Eden, nothing but a agrarian land.