Why does the male peacock have such a big and colorful tail? The classical Darwinian view of natural selection fails to provide a suitable answer. Natural selection principles suggest that those traits that enhance survivability will be selected. However, a peacock’s tail does not help it move faster, fly higher, or blend in. In fact, it hinders all of those functions. If not natural selection, then what other mechanisms are at play? Why is beauty being selected even though it appears to hurt the organism’s survival?
This question bothered Darwin, after all, natural selection could not explain everything. Eventually, he came to an answer of his own. In his lesser-known book, “The Descent of Man”, Darwin proposed another theory, that of sexual selection. This theory suggested that aesthetic preferences can also create selective pressures that compete with natural selection. In this view, one partner, generally the female, exhibits an aesthetic preference for certain traits and enacts them through choice. Their choice ultimately leads to males with those traits to be more successful in passing on their genes, and propagation of the aesthetic trait.
This idea still doesn’t explain why the aesthetic traits would become exaggerated. An answer to this comes from Ronald Fisher, known widely for his statistical work, but had important contributions to the fields of biology and genetics as well. Fisher described a process that combined both natural and sexual selection. He proposed that certain aesthetic traits may serve as signals for underlying genetics that confer a survival advantage. For example, a bird with vibrant plumage may signal that it is healthy. Over time, these traits may start to become noticed by the female of the species as reliable signals, creating an underlying aesthetic preference for them. This aesthetic preference further boosts the selection of males with those traits.
Here is where an interesting thing happens, a positive feedback loop is created. Those males which display these traits are more likely to be selected. In doing so, males that have an exaggerated version of these traits, brighter plumage, louder call, are selected for even more. This feedback process starts to tip the balance toward sexual selection alone, and eventually, the trait in question does not reflect a survival advantage, and in some cases may actually cause a disadvantage! Fisher called this process ‘Runaway Selection’ because the trait that once was an honest signal of underlying goodness has ‘run away’ and now has become a force of its own (see image below).
Is this runaway process limited to genetics, or can we apply it to social dynamics as well? For humans, evolution occurs not only in the genetic domain but in the socio-cultural domain as well. Therefore, it’s plausible that runaway mechanisms may be playing a role in shaping our social and cultural trends as well. To illustrate this, let’s start with an honest signal of social success. For example, social media has shown us that certain facial traits in females, like fuller lips, high cheekbones, and cat-like eyes, are associated with greater social desirability and influence. These traits signal youth and exoticness, which may have initially allowed certain social advantages, but later become a force of their own.
In a genetic setting, such traits would have to be propagated through repeated cycles of selection, with only those who can successfully display them being lucky enough to be selected. In a social setting, however, this process can happen much quicker through mimicry. If the successful and desirable members of one’s society display certain traits, it is beneficial for others in that society to mimic them in an attempt to be desirable as well. Crucially, this mimicry does not need to be genuine. For example, one can get cosmetic procedures like lip fillers in order to make their lips look fuller. In these cases, the trait has once again run away from the original underlying value and become a force of its own. For example, consider the billion-dollar make-up business by the Kardashian family.
Do social run-away traits get exaggerated as well? In theory, the same positive feedback loop and dissociation from the true underlying value should create exaggeration. A cursory study of wanna-be influencers shows that certain aspects have indeed become greatly exaggerated since their introduction to the social scene. For example, the emergence of hip slimming devices, glute enhancement surgery, etc.
If the runaway principle does exist in the social domain, what are its implications for a hyper-connected world where trends emerge and fade rapidly? Will we see greater amounts of exaggeration, or will the increased pace of social evolution lead to a decrease in runaway traits since new trends may emerge before enough positive feedback cycles are completed? How do social pressures compete with natural selection? For example, will some traits that are repeatedly selected due to their social advantage begin to be selected despite having a net survival disadvantage? Lastly, as we move from the real to the virtual world, mimicry will become easier and easier, will this lead to the emergence of new types of aesthetic runaway traits only possible in the virtual world? Many more interesting questions await as we apply theories from biological evolution to the social realm.
For more on this topic, I highly recommend reading “The Evolution of Beauty” by Richard Plum