One of my great frustrations in life is how evolutionary psychology, a fascinating scholarly subgenre that provides unique and valuable insights into many problems across the disciplines of biology and psychology, became evopsych. Click bait before there was click bait, evopsych is justifies whatever the author believes by using the (white, middle class, suburban families of the) 1950s as the evolutionary relevant time period. So now I can’t talk about cool things like costly signalling without a disclaimer that it’s not one of those evopsych articles.
Costly signalling is the act of doing something stupid to prove your genes are so good you can afford to do so. The most popular example is the peacock’s tail: it is energetically expensive and makes you attractive to predators. Surely if you have it you must posses many great genes that I, a female peacock, would like to secure for my offspring. The tail is also a canvas for parasites, so if it looks good, you must not have many. That is good for me and implies good genes for our future offspring. Let the peacock sex commence. Costly signalling doesn’t have to be about mating. Certain ugulates will signal a predator that they see them and are not worth chasing by stotting (jumping in a uniquely pointless way).
The key here is that the signals are very expensive. A weak peacock who attempts to grow a beautiful tail will be eaten. A weak ugulate will have an unimpressive stot. Males of a bird species whose name I can no longer remember get more female attention when their breast is redder, but are also challenged more by other males. Males artificially reddened by experimenters temporarily attract more females, but they also attract more fights from other males, and are ultimately worse off. That cost is what makes the signal work.
My second favorite
theory hypothesis speculation about humans and costly signalling is that it, and not utility, led to male upper body strength. If the hypothesis that humans broke out from the other hominids via endurance hunting is correct, upper body strength is mostly dead weight. Useful in some circumstances, but a cost during hunting. I want to be really really clear that this is basically me making something up after reading a book that wasn’t even that scientific, but you have to admit it would be super interesting if it were true.
My favorite speculation about humans and costly signalling is the Scheherazade effect, which I learned at school rather than making up but is only slightly proven. The Scheherazade effect can refer to two related but distinct things. The first is that individual humans can signal how much energy they have to spare (implying they are good hunters or have efficient energy usage elsewhere) with pointless feats from our most energy intensive organ: the brain. Humor? Art? Chess? All attempts to impress the opposite sex. This + the fact that male reproduction is tournament-style and female reproduction is roughly linear with respect to fitness may explain why men are more likely to pursue truly stupid wasteful hobbies.*
The second Scheherazade effect is the cumulative effect of the first. After tens of thousands of generations, individual attempts to impress one another via kick ass drumming actually humans better at drumming. Or juggling. Or story telling. Or joke telling. Or that it may even be the origin of language itself.
The Scheherazade effect is unfortunately untestable, so it’s only real use is to parallel “he’s so hot” when telling your friends about someone who became impressive to you via feats of intellect. But if you travel in the right circles, that is pretty useful.
*Although it is impossible to separate this effect from that of socialization.