Did we evolve big brains to be sexy?

If you look at the world around us, it's brimming with art, music and technology. But painting, humour and music don't contribute to survival, so why did they evolve? In his book The Mating Mind, Professor Geoffrey Miller argues that a process called sexual selection, which causes "sexy" traits to remain in the gene pool, could be at the heart of many of humanity's unique features, as he explained to Georgia Mills...

Geoffrey - Bare in mind, every single one of your ancestors all the way back millions of years, succeeded not just in surviving and making a living but also attracting a mate, keeping them around long enough to raise kids together and, basically, being sexually and romantically successful.  All of our would-be ancestors who failed to attract a mate, no matter how good they were at surviving, did not pass on their genes and did not become our ancestors.

Georgia - This drive to reproduce means we have traits that make us sexy but that don't necessarily help us to survive.  Think about the Peacock's tail - it's probably not going to help them avoid being eaten - probably the opposite.  But the big feathers and bright colours show off the male's genetic quality, so females rather like them, and us humans have our own versions of the peacock's tail...

Geoffrey - I think in humans, we have physical equivalents.  Things like male beards, male upper body muscles, female breasts and buttocks.  Any traits that are elaborated beyond the requirements of surviving and parenting.  But beyond that, we have mentally attractive traits that are also romantically compelling - things like intelligence, creativity, sense of humour, artistic and musical abilities, and even moral virtues.

Georgia - You kind of just listed almost everything about people there in one go.  Why would someone find these traits attractive?

Geoffrey - I think these traits are all attractive because they testify that your brain works pretty well.  It's hard to produce these if you've got brain damage, or if you're the result of siblings, or cousins getting married and having genetic inbreeding problems, so it's a pretty good testament to your brain quality and, in turn, you genetic quality.  So I think that's why we pay a lot of attention to these, we're doing a sort of unconscious quality assessment. 

It's something Freud talked about a century ago.  And I'm by no means a fan of Freud but I think he was on to something that, if we were only motivated to survive to take care of our kids, an awful lot of human civilisational achievements would not have happened.  An awful lot of art and music and intellectual progress would not have happened if we hadn't had this drive to attract mates. No doubt, intelligence itself is useful in every possible domain of life.  But things like sense of humour are so bizarre because you can't scare away a sabre tooth cat by making a joke at it.  It doesn't really help you find nuts and berries in the wild, but it's very useful socially and it's particularly useful in sexual and romantic contexts.

Georgia - You mentioned music and I know when I think about guitar playing, people in bands - they're quite attractive.  And you argue that this is sort of a sign that your brain works well, there's positive things going on behind the scenes.  But then if you think of someone who's maybe a chess player doing really well, I can't see the same 'fandom' breaking out about it.  What's the difference there?

Geoffrey - Yes, there's a crucial difference between music and chess in that our ancestors were making music to attract each other for at least 30,000 years.  We have good evidence from bone flutes from Germany.   So we know music is ancient, and that means we could evolve, made preferences to be attracted to music.  Chess, on the other hand, is only about 1,000 years old so we haven't really had the instincts to find grand masters romantically compelling but, if we wait another 10,000 years, it might be that chess becomes as romantically compelling as music is now.  It's hard to predict those things but it's quite possible.

Georgia - You also mentioned kindness, morality, and I know that's something that has sort of natural selection a bit stumped because the whole idea is, you go after something that improves your own survival.  So how would sexual selection explain morality?

Geoffrey - If you're somebody, particularly as a potential long term partner, you really want to be able to trust them, communicate effectively with them, be confident that they have your best interests at heart.  So our ancestors would have favoured mates who have the moral virtues that predict being a good partner and a good parent and that, I think, is important on Valentine's day when you're basically doing signs of romantic commitment to say look, here are my moral virtues as they relate to my love for you.  Here's how I express them.  And then if that succeeds somebody goes 'ahh, they're a good person, good boy, good girl, I want them, I can trust them.'

Georgia - I mean the message there is kind of half sweet and half a bit depressing like they're being kind to you but it's just to keep you on side - it's all part of the long game...

Geoffrey - Yes.  I mean that's the funny thing about virtue signalling is that you're kind of showing off your innermost qualities in a somewhat ostentatious way.  And when it comes to people giving lots of money to ineffective charities, that's a bad form of virtue signalling because they're just burning money and saying, look look at me, I'm so generous.  But when it comes to romantic things like writing, you know, erotic poetry or skyping with your beloved when they are away at a conference, that's good stuff.  That actually does deliver real value to the other person and it testifies to your moral virtues so, I think, that stuff is great.