Countless television programs and movies portray casual sex as “no big deal,” or even normal. But according to the scientific data, that view is all wrong. As it turns out, the brain chemistry associated with sex is exclusively conducive to marriage.

Doctors Joe McIlhaney and Freda McKissic Bush laid out the scope of current medical knowledge regarding casual sex in their 2008 book Hooked: New Science on How Casual Sex Is Affecting Our Children.¹ Increases in dopamine, a brain chemical that gives a sensation of satisfaction, accompany exciting and rewarding experiences. This stimulates a desire for more of the activity that brings the sensation. However, the authors noted that dopamine is values-neutral. The same dopamine-associated sense of well-being can result from both good and bad, healthy and harmful actions.

According to McIlhaney and Bush, when a woman is touched in a loving way, her brain secretes oxytocin, which activates feelings of closeness and trust. Breastfeeding has a similar effect, encouraging mommy-baby bonding. More intimate physical contact produces more oxytocin, which leads to a greater desire for that close feeling.

Oxytocin production, like dopamine, is not controlled by conscience or consciousness, but is a physiological effect of intimate contact. When this is experienced outside the commitment of marriage, the authors noted that women can become deceived into thinking a bad relationship is good because of the effects of touch-dependent oxytocin. And when that relationship ends, the broken bond and feelings of betrayal of trust can lead to severe emotional trauma.

For men, an effect of vasopressin—which floods a man’s brain during intercourse—is that it leads to a bonded feeling with his partner. Research shows that if he has intercourse with multiple partners, the bonded feeling is dissipated, eventually imperiling a man’s ability to form long-term attachments.

Evolution is only “interested” in mankind having an effective anatomical mechanism to propagate. Any biological imperative to mate and pass on one’s genes would not necessarily be tied to a long-term relationship. On the contrary, the more partners one has, the more opportunities there are for diverse offspring.

But the human brain appears to be specifically designed to encourage monogamous, trust, and commitment-based marriages—even to the point of possessing intricately coordinated brain chemical production and detection wired to touch sensors to produce feelings of intimacy.

These intricate features of human brains match well with God’s design for marriage. The existence of these bond-encouraging physiological systems is just what would be expected from a Creator who intended a married couple to become “one flesh.”²

The texts of both Hooked and of Scripture indicate that those who follow God’s monogamous plan for sexuality—whether intentionally following the Bible’s instructions or not—have healthier and happier relationships with their spouses.

References

1. McIlhaney, J. S. and F. McKissic Bush. 2008. Hooked: New Science on How Casual Sex Is Affecting Our Children. Chicago, IL: Northfield Publishing. For a review of the book, see Segelstein, M. The science of sex. One News Now. Posted on onenewsnow.com June 16, 2009, accessed June 24, 2009.
2. Genesis 2:24.

* Mr. Thomas is Science Writer at the Institute for Creation Research.

Article posted on July 14, 2009.