Hormones are powerful. I know this from personal experience, as I was put on steroids as a kid to make me grow, and it did a number on me.

Hormones can have unintended consequences, and I have often wondered about whether birth control pills might do more than simply prevent pregnancy.

The evidence accumulates that they do:

To millions of women it has been the great liberator over the past four decades, allowing them the freedom to control their fertility and their relationships. But the contraceptive Pill could also be responsible for skewing their hormones and attracting them to the "wrong" partner.

A study by British scientists suggests that taking the Pill can change a woman's taste in men -- to those who are genetically less compatible.

The research found that the Pill can alter the type of male scent that women find most attractive, which may in turn affect the kind of men they choose as partners. It suggests that the popular form of contraception -- used by a quarter of British women aged between 16 and 50 -- could have implications for fertility and relationship breakdowns.

The findings, from a team at the University of Liverpool, add to growing evidence that the hormones in the Pill influence the way that women assess male sexual attractiveness.

[...]

Commenting on the latest study, the researchers said that it could indicate that the Pill disrupts women's ability to judge the genetic compatibility of men by means of their smell.

They said that this might not only impact on fertility and miscarriage risk, but could even contribute to the end of relationships as women who stop or start taking the Pill no longer find their boyfriend or husband so attractive.

So assuming these latest reports are correct (and assuming you're heterosexual and looking for a mate), probably another good "test" of a relationship would be to stop the hormones, and make sure the attraction is really on the level.

However, a lot of this stuff is psychological, and the trick is to figure out how much of it is really instinct, and how much is "in the mind." I'll never forget a divorced friend with two kids who didn't want more, so he'd had a vasectomy. During the dating process, he fell head over heels for a woman who claimed she "didn't want children." He assumed she meant it, but dated her for some time without disclosing the vasectomy. Finally, he got up the courage to tell her, and she dropped him like a hot potato. Assuming she was honest, her instincts were probably stronger than her stated desire not to have kids. Or perhaps she was mugged by the uncompromising finality of a vasectomy.

This all begs the question of what is love.

Is it all in the mind?

Or all in the hormone/chemistry/instinct nexus?

It's sobering to think that love -- a philosophical question challenging some of the greatest thinkers in history -- might come down to simple chemistry.