Aesthetic evolution

 This post will look at some of the potential implications for evolutionary theory of two books for the general reader, both published fairly recently. These are The First Minds: Caterpillars, Karyotes, and Consciousness by Arthur Reber and Richard Prum's The Evolution of Beauty: How Darwin's Forgotten Theory of Mate Choice Shapes the Animal World - and Us.  If the central arguments of these two books are accepted and juxtaposed with each other, the implications for evolutionary theory are very deep. 

 The following thoughts, based on my reading of these books together,  don’t entail any particular metaphysical assumptions (whether panpsychist, physicalist or idealist), apart from the assumption that consciousness can influence behaviour. For an argument regarding why this assumption is probably correct, see this post. 

Sexual selection is the terms used for evolution resulting from the preference by one sex for certain characteristics in individuals of the other sex. The crux of Pum’s argument is that sexual selection can cause traits to evolve for no other reason that they are pleasurable. So, for example, things like bird plumage or mating displays may do nothing to increase the ability of peacocks to survive other than impressing the mate. This gives rise to positive feedback effects whereby the trait and the preference for that trait co-evolve with each other.  

For example, if a bird has an aesthetic preference for mates with long tail feathers, birds with such tails  will be selected for. The result of this is that genes for the preference for long tails will become correlated with genes that produce long tails. So, if a bird with a preference for a long tail selects a mate with a long tail, the probability that the offspring will be a bird with a long tail who also has a preference for long tails will be increased. This gives rise to what is known as the Fisherian runaway effect, in which things like long tails can become longer and more widespread due to mate choice, independent of other effects the trait may have on survival. Thus, long tails could increase in prevalence and length due to sexual selection, even if they make the bird more susceptible to predator attack.  

The runaway effect is an uncontroversial feature of contemporary evolutionary theory. The only dispute is over how widespread it. Darwin himself emphasized the importance of sexual selection in evolution, but over the years emphasis on it diminished. Prum’s book argues that sexual selection deserves more attention.  

Prum argues that part of the reason for the lack of focus on sexual selection lies in the effects of the shameful association of evolutionary biology in the first half of the twentieth century with eugenics (which is the advocacy of “improving” the human species by preventing some people from reproducing and encouraging others). Although eugenics has been universally rejected by contemporary evolutionary biologists, Prum argue that “some core, fundamental commitments of eugenics were “baked into” the intellectual structure of evolutionary biology” (p. 526). One of the effects of this is that “[o]bvious and uncomfortable intellectual similarities remain between eugenics and current adaptive mate choice theory” (p. 527). Thus, Prum argues that there in an in-built bias in evolutionary biology has led to a minimization of the impacts of sexual selection. 

Turning now to Reber, the core argument of his book is that consciousness arose in single-celled organisms. Note that although it could be argued from a panpsychist perspective that consciousness existed in some form or another even prior to this, this issue is not relevant for the purposes of this post. What is of interest here is combining Prum’s views on sexual selection with Reber’s position that every organism from bacteria upwards has some form of consciousness within it. 

It is possible that sexual selection goes all the way down to bacteria (see this article for example). Thus, if Reber’s argument is accepted, then it is also possible that the subjective preferences of organisms all the way down to bacteria have had an impact on evolution.  So, just about any trait could potentially have been influenced in some way by the subjective preferences arising from mate choice. Subjective preference here refers to aversion or adversion to stimuli. Or, in simpler terms, pleasure seeking and pain avoidance. 

To give an example, this video shows conjugation (exchange of genetic material) of protozoa. Some of the areas where sexual selection could potentially  play a role here include tactile responses, chemoreception, texture and movement. For instance, if the protozoa have a preference for a certain type of pulsatory movement of the protozoan body or cilia in the partner it selects, then that motion could be selected for regardless over whether it confers survival value in other ways (for example, by increasing the speed with which the protozoa escape from predators). In fact, even if a certain motion slowed escape from predators, it could still be selected for if the aesthetic preference, or pleasure-directed behaviour, of the protozoa outweighed the disadvantage of being slower.

 Considering that all the cells and organs in multicellular organisms are derived from single cells, which evolved from single celled organisms whose characteristics may have an evolutionary history impacted  by sexual selection, the potential impacts of sexual selection could be very broad. For example, rhythms, movements, shapes, patterns and textures of organisms and their parts might all have been influenced at various stages of their evolutionary history by subjective preferences and mate choice. 

This is all very speculative of course, and it would be up to actual scientific experimentation and empirical research to discover how deep the effects of sexual selection go. But if the assumptions that subjectivity affects behaviour and is present in all organisms ever became part of mainstream biology, factoring in sexual selection could change the entire edifice of evolutionary theory, with wider impacts upon how all modern people conceive the world. Rather than solely being a story of ‘survival of the fittest’ the living world could thence be seen as a result of both pleasure seeking and the struggle to survive, a dialectic of sexual selection and natural selection.  

Prum argues that to “permanently disconnect evolutionary biology from our eugenic roots, we need to embrace Darwin’s aesthetic view of life and fully incorporate the possibility of nonadaptive, arbitrary aesthetic evolution by sexual selection” (p. 528). Combining Prums’s views with Reber’s expands the scope of this aesthetic view of life even further.