Smell anyone nice lately? Did it make you feel a little, you know, frisky? (That’s another word for romantic, kids.) Well, you are not alone. In fact, the entire rest of the human race is with you on that one. And what’s more, we have evolution to thank for it. Because according to some theories (and, in fairness, to some interesting research studies), natural selection has favoured the evolution of human mate selection through smell. Basically, we have evolved an “if-it-smells-right-do-it” kind of instinct.
This is because the person who smells nicest to you will likely have the best immune system for you. Not only will they live longer with you, but because you and he/she will be so compatible, your offspring will have super-duper-healthy immune systems as a result. Such is the power of major histocompatibility complex (MHC) genes. Or at least that’s the theory.
Journalists often like to write about these types of theories. In fact, if any theory involves evolution and sex (not an entirely unheard of combination, I grant you), then the media are likely to get interested sooner or later. And who can blame them? It is certainly intriguing. I think readers will genuinely be interested in explanations of their own sexual urges that somehow invoke our troglodyte ancestry. But given that most people’s understanding of cavemen and their sex lives owes no little debt to, well, the way Fred Flintstone used to look at Wilma, such theories (and associated research) can pose difficulties for reporters.
Today’s Irish Examiner did quite a good job of navigating these difficulties. But then I would say that, wouldn’t I? After all, I myself was quoted at length throughout the piece. Ker-tish! You can read all about it here.
I always really loved this advert. Now, in the name of science, I get to introduce it to a whole new generation...
In a nutshell, the difficulty with stone-age-brain-in-present-day-skull theories tend to relate to two problems, both of which I managed to mention in the Examiner article.
The first problem is the fact that evolutionary progress is outstandingly slow, so slow that it almost defies human comprehension. By way of classroom example: If the entire history of evolution was compressed into one day, then homo sapiens themselves would just be coming into existence at around 11:30 p.m. They’d barely have learned how to talk before it was two minutes to midnight.
The problem here is that, because of the excruciatingly slow pace of natural selection, even a tiny difference in our physiology or psychology will end up making a big difference to our evolutionary trajectory over time. So even if a tiny number of people could detect a tiny difference in the way potential lovers smell — and if such an ability ended up causing even a teeny weeny benefit to their health and that of their offspring — then it is likely that such a difference would be favoured by natural selection. But because all these factors would be so tiny, we wouldn’t be able to notice them.
So just because some genes that affect immunocompatibility also affect the way we smell, it doesn’t mean that we would ever be consciously aware of it.
The second problem is the fact that evolutionary processes have, by their very nature, preserved features that will have been useful to our ancestors, and not necessarily to us. In fact, because the vast majority of our own personal ancestors (i.e., our great-great-great-great-great-great-etc.-etc.-grandparents) lived in the world before our species thought it might be nice to actually cook meat before eating it, you can take it that there is much about our physiologies that is nowadays obsolete.
Therefore, our ability to choose a suitable mate by smell (even if it were significant) would not necessarily do you or me any good. It might make our kids that bit more resistant to some prehistoric bacteria that were doing the rounds 200,000 years ago. Who knows? It might even help them live through their 20s without dying of, say, old age.
In other words, we’re unlikely to see the benefit ourselves. Those millennia are long gone.
While we're on the subject...
I’m happy to say that the Irish Examiner journalist, Arlene Harris, did a great job in bringing these points out in her piece (albeit by quoting me at length). This is nice to see because the points are relatively subtle, and many news stories on science subjects actively avoid subtlety and abstraction as much as possible.
Note to journalists: When reporting on evolutionary psychology, be sure to mention that evolved behavioural adaptations will nearly always be (a) unnoticeably tiny and (b) irrelevant to our modern lives.
Failing that, just give me a call.
Brian Hughes is an academic psychologist and university professor in Galway, Ireland, specialising in stress, health, and the application of psychology to social issues. He writes widely on the psychology of empiricism and of empirically disputable claims, especially as they pertain to science, health, medicine, and politics.