Birth control and abortion options, which have expanded considerably in the past 40 years and are hailed by feminists as emancipating women, seem to give both sexes the mistaken notion that they can have brief sexual encounters with serial partners and face no consequences that can’t be handled by clinic visits.

For men, that remains somewhat true — or as true as it has been throughout history. However, for women, that is as untrue today as it has been since the first humans walked on Earth. The reason is oxytocin.

“Love is the drug” and oxytocin is that compound! When pumped into the bloodstream, oxytocin acts as a “neuromodulator,” giving people the warm-and-fuzzies and increasing the emotional bond between that person and the second individual (whose presence is stimulating the production of this hormone).

Oxytocin’s power is not to be underestimated.

During millions of years of human evolution, the female system has been designed to begin a cascade of oxytocin production during two specific events: 1) When being intimate with a man; 2) When breast-feeding an infant. On the other hand, human males have very limited oxytocin levels (and actually release some of the little oxytocin they produce during “extracurricular activities”).

Now, oxytocin is a wonderful thing. It energizes people, and makes them feel good about life. It enhances the immune system, as well as boosts other biochemical processes in the human body.

However, as with everything else pleasurable in life, there is a downside. Once a woman generates oxytocin, she will usually want to do everything in her power to keep up the production levels. For example, there are tales of women who nurse their babies past toddler-hood (until 3, 4 or 5 years in age). These women want to continue releasing oxytocin (even though they will have other rationalizations).

The same thing is true following intimate relations. Oxytocin production can be stimulated in a woman through her lover’s voice, scent, sight and touch. This fact explains a wide range of female behaviors that follow intimacy. For example, women will call up their new partner frequently. They will steal their lover’s shirts to enjoy the scent. They will invent excuses to see the man-of-the-moment. And the more oxytocin these women generate when with their lovers (or by talking to them), the more emotionally attached they get.

Ever wonder why woman goes back to a man who beats and abuses her? Or question why supposedly smart women can’t make up their mind whether to dump boyfriends that impregnate someone else? How about ex-girlfriends who call endlessly? Then, there is the scary extreme of stalkers.

Since casual hookups and broken relationships can cause such emotional harm, would not early marriage, like before eighteen years, avoid this?

Read the last paragraph in the OP's opening quote. proximity to the 'man-of-the-moment', nothing about feeble women brains being enslaved to a single male figure for the rest of their lives.

This isn't even casually true on a biochemical level. Oxytocin does not just produce warm fuzzy intimate feelings. Studies suggest that oxytocin creates intergroup bias because oxytocin motivates in-group favoritism and, to a lesser extent, out-group derogation.

Ever wonder why woman goes back to a man who beats and abuses her? Or question why supposedly smart women can’t make up their mind whether to dump boyfriends that impregnate someone else? How about ex-girlfriends who call endlessly? Then, there is the scary extreme of stalkers.

Since casual hookups and broken relationships can cause such emotional harm, would not early marriage, like before eighteen years, avoid this?

Which means oxytocin partially explains racism.

Indeed, Memnon. I wasn't trying to say "Oxytocin doesn't do 1 thing, it does 2," but more "narrowing down a chemical in the brain to any small set of activities is almost always destined to fail miserably." Most neurotransmitters and neurochemicals operate on multiple levels and influence behavior in multiple, often contradictory ways.