The Chemistry Between Us: Love, Sex, and the Science of Attraction

by Larry Young

Testosterone will drop in certain contexts besides missing testicles. When male marmosets sniff a test tube containing the scent of their own infants (but not strange infants), their testosterone drops within twenty minutes. This could be a protective mechanism, a way of tamping down a father’s sex drive and aggression when he’s around his babies. Studies in humans have shown that when men become fathers (and especially when their babies are newborns), they experience a significant drop in testosterone. Men who are very involved in parenting their babies show the biggest drops—probably because the act of caregiving itself lowers testosterone and allows the brain to focus more on nurturing and less on fighting (even if it’s only a job promotion at stake), sex seeking, or anger. Testosterone falls when we lose a sports match, and it even slumps when the team we root for loses a game. (Sorry, Cleveland.) Driving an old, clunker family car reduces a man’s testosterone levels. Long-married men have lower testosterone readings than single men do (read into that what you will). Being fired from a job isn’t good for our levels, either. Though menopause reduces sex hormones more dramatically in women, aging men still experience a significant falloff.