You may have heard that symmetry is scientifically attractive. This statement is true, but incomplete. Symmetry is just a smaller component of a broader trait.
Here, I will revisit a website I have linked previously on my blog, this. It allows you to combine faces. Personally, I think that all of the people’s faces are ugly. But, the more you combine them together, the more attractive the average face is.
How can we explain this? Well, when you average together faces, you iron out the bad idiosyncrasies. Most faces have flaws, but most faces don’t have the same flaw, so the cumulative of each part of the face aggregates to no flaws.
As a contributing factor, people’s flaws happen in opposite directions. For example, nose-too-small vs nose-too-big average together into an average size nose. In this excerpt from The Black Swan, Nicholas-Taleb explains how random, independent deviations can “average out” into normalcy:
[In normal distributions] no single observation will impact your total. This property will be more and more significant as your population increases in size. The averages will become more and more stable, to the point where all samples will look alike.
I’ve had plenty of cups of coffee in my life (it’s my principal addiction). I have never seen a cup jump two feet from my desk, nor has coffee spilled spontaneously on this manuscript without intervention (even in Russia)…
Yet physical reality makes it possible for my coffee cup to jump—very unlikely, but possible. Particles jump around all the time. How come the coffee cup, itself composed of jumping particles, does not? The reason is, simply, that for the cup to jump would require that all of the particles jump in the same direction, and do so in lockstep several times in a row (with a compensating move of the table in the opposite direction). All several trillion particles in my coffee cup are not going to jump in the same direction; this is not going to happen in the lifetime of this universe…
Coming back to attractiveness, we can gleam that it’s caused by what we can call “facial averageness,” of which symmetry is a property. The average face is a face with no flaws.
To gain insight into facial averageness, it is instructive to go on a digression about identical twins.
Identical twins are not exactly identical. But some are more identical than others. Some identical twins look almost exactly the same, whereas others aren’t exactly “identical.” This is interesting, given that identical twins share the same genes.
What’s more interesting is that you can witness a smaller version of this on your very own body: symmetry. Where there is symmetry, the same genes are largely responsible for determining the traits on both sides of the body.
The same genes control, say, the shape of both ears. So, in theory, the two sides of your face are mirror “twins” of each other. Despite this, the two sides of your face are not exactly the same. This program allows you to compare the sides of your face. You can compare the symmetry of various celebrity faces here.
A frequently asked question is, “why hasn’t ugliness been selected out of human populations?” There are a lot of factors to the answer of that, and it goes beyond the scope of this post. But one possible answer is that it’s not the genes that are are at fault, it’s the extent to which your appearance can vary, given the same genes. And, because the “flawless average” is selected for, this also represents the amount your face deviates from that.
There seems to be a sort of meta-evolution going on, with some genes expressing themselves strictly, and other expressing themselves loosely. The former represents a low-risk strategy in evolution, while the latter is a high-risk, high-return strategy.
The former strategy is to stay close to the middle of the bell curve, while the latter strategy experiments with the edges. While the latter can create ugliness (by leading to flaws, deviations from the normal), deviations can also have rare upsides (see: this post).
In humans, men are considered the sex that judges more based on attractiveness. What they’re actually judging, in part, is that the low-risk strategy is obeyed. Women have other things to judge on, and it should be noted that humans are a bit unique in this regard.