To what extent do you think human psychological traits are evolved adaptations?
In 1859 Charles Darwin published his most famous book, ‘The Origin of Species’, in which he outlined his theory of evolution. The idea was that a population, over time, becomes increasingly adapted to the environment within which it is contained, as organisms within that population who possess desired traits – ones that may increase the chances of survival – are naturally selected for, and thus are able to pass down these traits to their descendants through genes in their genetic code. These desired traits are able to then easily spread throughout the population, as those organisms who do not possess them are outcompeted and therefore die off.
We can see evidence of this in the real world around us. There are many examples that have taken place over a short enough time period for them to be observed and studied by humans. One is the notion of bacterial antibiotic resistance. Humans have developed antibiotics in order to combat pathogenic bacteria such as Mycobacterium tuberculosis which causes the disease commonly known as tuberculosis. However, bacteria are very good at quickly passing on a gene which may code for a protein that enables them to survive against a certain antibiotic. They are able to do this by dividing extremely quickly via mitosis, and are even able to exchange genetic material between each other by connecting through thread like extensions called pili that protrude from their cell membrane, and then exchanging loops of DNA called DNA plasmids. This is a process known as bacterial conjugation. For these reasons they are quickly able to gain resistance against a certain antibiotic, if a random mutation in the DNA occurs that allows this to happen. Penicillin, the first ever developed antibiotic, by Alexander Fleming in 1928, is now useless against a myriad of diseases caused by bacteria, such as Gonorrhea caused by Neisseria gonorrhoeae and the MRSA infection caused by Staphylococcus aureus.
Another example of observed evolution involves peppered moths during the industrial revolution in Britain. Before the revolution, birch trees were a pale silver colour. Thus, in order to remain camouflaged and thus hidden from their natural predators, the overwhelming majority of peppered moths in urban areas were coloured that same pale silver colour. This, of course, vastly increased their chances of survival. However the advent of mass scale industry, let to air pollution like never before, and soon the vast quantities of soot released into the air from the combustion of coal stained these trees a much darker black colour. The silver moths were therefore at a large disadvantage in terms of their ability to hide from predators and thus survive. On the other hand, the black moths now had a survival advantage, and by the mechanism of natural selection, they increased their numbers to the point that they massively outnumbered their pale silver counterparts. This type of selection is known as directional selection, as the favored phenotype is an extreme
one, so there is a radical shift in the allele frequency that codes for that phenotype.
These two examples that have been outlined, both demonstrate the way in which natural selection works, in the context of the real world. However, there is one large caveat which must be noted; both these examples involved physical changes in the organisms’ phenotype, in that the traits they developed were both entirely tangible – the bacteria developed antibacterial resistance, and the change in the moths was observable – a change of colour. On the other hand, humans, as well as some other highly developed animals, pertain another level of complexity – their mental traits and psychology. It would naturally follow that, if it is possible for somatic evolution and the ability to adapt to one’s surroundings on the physical level, it should equally be possible for psychological traits to be evolved, whether by natural selection, sexual selection, or even genetic drift (evolution caused entirely by chance). Indeed, Darwin himself believed whole heartedly in this idea, saying that “Psychology will be based on a new foundation”. For this reason, he can be seen as the father of what is now known as the field of evolutionary psychology.
There are certain mental traits that humans possess, which are a necessity for the survival of the species. Perhaps the most obvious of these is the inherent desire to mate and reproduce. This is a trait as essential to the survival of the species as the urge to eat and drink. Any organism that fails to reproduce is by definition selected against. It can therefore be derived that the desire to reproduce must be evolved, since any organism lacking it will fail to reproduce and pass on the gene to successive generations. When this was first hinted at by Darwin’s ‘Origin of Species’, it sent shockwaves through society. It shattered the image held of the human race at the time. We were no longer a species divinely elevated above others, but of course now a species on the same animalistic level. We must have evolved from the same common ancestor, and therefore possess all the troglodytic traits that we perhaps tried to hide using the veil of our opulent civilization. The famous book ‘Strange Case of Dr Jekyll and Mr Hyde’, written by Robert Louis Stevenson in 1886, was very much a reaction to this inconvenient revelation, and epitomises the arrogance of the attitude at the time. Dr Jekyll is, during the day, an upper class doctor surrounded by the lavish luxuries of his rich life. He socialises with equally dignified friends, however he uses this stately routine only as a façade for his wrong-doings during the night, where he engages in sexual conquests with prostitutes and commits brutal crimes, as a much changed Mr Hyde. This book is of course a reminder of our true selves. Much of our psychology, on the most basic level, is geared towards reproduction and the assurance of the continuation of the human race as a biological species. We are evolved to make sure that this is the case, as much as we may like to turn away from it or pretend that it is not there.
More interestingly though, are the mating strategies that have developed in humans, and also what characteristics make a mate more desirable. The ways that men and women go about searching for a partner are both very different, as well as the characteristics that are desired.
The reasons for these differences, can be explained by the different physical challenges that arise for males and females when attempting to reproduce (Buss, 2016). On the one hand, women, have to put a great investment into the pregnancy and raising of a child, whilst on the other hand, males need not invest a great deal of energy. The only challenge arguably that has faced males is paternity uncertainty – that is the concern that it indeed was him who was responsible for the conception of the child, so that he may pass on his own DNA. To deal with these challenges, males and females have their own psychological adaptations.
Females are highly selective when it comes to who they choose as their mate.
Jealousy is a human psychological trait (present in both males and females) which also could have evolved due to the basic need to keep a mate for reproduction, to ensure one’s own genes are passed on. It could perhaps be seen as a process that drives an individual to overcome the threats to the retention of a mate. To put this in context, we must look situations which bring rise to emotion of jealousy. One example, is when one sees his or her partner in the presence of other members of the opposite sex, in particular when the other person appears to be acting flirtatiously or attempting to seduce him or her, perhaps to try an engage in a sexual relationship; an act which is known as mate poaching (Buss, 2016). The threat of a partner’s infidelity may mean that the partner ends up mating with someone else, resulting in the failure to pass on one’s genes. It therefore makes sense that sexual selection has favored those that have a mechanism of protecting against a mate from being poached. The evolved trait thus must be jealousy. It causes an emotional response which effects the person to behave in such a way that he or she aims to safeguard his or her own genes through preventing a partner from acting unfaithfully or going astray. It makes one more vigilant as to the actions of one’s partner but also increases the amount of effort one may put into fulfilling the desires of one’s partner, with the goal of retention.
Men and women both experience jealousy to the same magnitude, but according to David Buss, the causes of them for each sex is slightly different. He asked 511 college students were asked to determine which they felt was the worst of two scenarios; the first being their partner being sexually unfaithful, but the second being where their partner was emotionally unfaithful and becoming ‘emotionally involved with someone else. The results were fascinating. The majority of females (83%) found the emotional unfaithfulness to be more upsetting, whilst the majority of men (60%) found that sexual infidelity was of greater distress. This, of course, reveals a stark difference between the mating strategies of males and females. Since the primary problem for males is paternity uncertainty when it comes to reproduction, they are more fearful of their partner having sexual relationships with another man; that is the fear of being cuckolded. On the other hand, a woman requires a man to look after her, and invest time and effort in aiding her through pregnancy and the bringing up of the child. It therefore makes sense that they are far more fearful of their male partners becoming emotionally invested in another woman. Jealousy is therefore subtly different for men and women; the effect of the emotion may be the same but its cause is rather different.
The aforementioned traits, have all clearly been evolved. Each one seems only a natural response, or adaptation, to an obvious challenge being faced by humans. There are other traits we possess though, which seem rather more inexplicable. One of these is the human love of music. At a surface level, the fact that we can become so deeply captivated by harmonically structured sound, seems not only counterintuitive, but perhaps even irrational and a selective disadvantage. The world we live in is highly competitive, and at times extremely hostile and dangerous. Anything that has the ability to completely take our focus away from the world around us would therefore leave us vulnerable to the elements, or natural predators. It would be incredibly dangerous for one of our ancestors to divert his focus onto a sweet birdsong. He would be left exposed and unaware. It is therefore something of a mystery as to why we can be so captivated by music. However, there are a few possible explanations.
The first is Geoffrey Miller’s display hypothesis. This suggests that humans produce art in order to increase their attractiveness towards the opposite sex, to increase their chances of mating. He said ‘as every teenager knows, … cultural displays by males increase sexual access’. His theory would then suggest that men would produce art in greater quantities than women, since women have less to gain from a short-term sexual encounter as I have previously talked about. Men should also be producing more music in their 20s and 30s, when competition for mates is at its highest. Amazingly this is a pattern that has indeed been observed in the jazz industry. The graph below (fig 3) was produced by David Buss using data from The Essential Jazz Companion (1998) by Fairweather. A completely random sample of 1,892 Jazz Albums was taken, and then the age and gender of each artist was recorded, so that the graph below could be produced. On first glance, it appears that it could actually support the display hypothesis, however when analysed in more detail there are a few gaping flaws that appear.
The most apparent problem with the graph is that it does not account for gender bias regarding the music genre of jazz. For whatever reason, the production of jazz music may be a male dominated industry. There may be sexism in the industry, for example. There are also issues with the random sampling, and the reliability is therefore rather low. To draw comparisons between genders may not be so valid in this case, however this does not mean that the display hypothesis is entirely wrong. The fact that the majority of jazz artists are in their late 20s and 30s does support the theory, in that younger males may produce more music as this is the time of the most mating competition.
The primary issue here though, is with the display hypothesis itself. In fact, it explains very little. For example, it does not reveal to us why we find music so emotionally appealing and moving. It would be hard to argue that Mozart’s requiem was produced purely as the result of sexual competition. Secondly, it does not explain why we enjoy listening to music by ourselves, in a solitary environment. To explain this, we will need a better theory.
Steven Pinker argues that the reason we are inclined to exhibit a response to music is as a by-product of other psychological traits which we have evolved. He calls it ‘cheesecake for the mind’ saying:
‘We enjoy strawberry cheesecake, but not because we evolved a taste for it. We evolved circuits that gave us trickles of enjoyment from the sweet taste of ripe fruit, the creamy mouth feel of fats and oils from nuts and meat, and the coolness of fresh water. Cheesecake packs a sensual wallop unlike anything in the natural world because it is a brew of megadoses of agreeable stimuli which we concocted for the express purpose of pressing our pleasure buttons.’ (From How the Mind Works by Steven Pinker, 1997).
Pinker is saying that the reason we enjoy cheesecake, is because we have evolved the ability to enjoy many of the things that make it up, such as the sweetness of fruit or the refreshing nature of water, but not because we have evolved to like cheesecake itself. In this way, cheesecake could be seen in exactly the same way as music. We do not enjoy music because we have evolved to enjoy music itself, but because we have evolved to become very well adapted to other things, which result in us enjoying music. For example, we have evolved the ability to understand each other and communicate through the use of language, and as a byproduct of this, the lyrics contained within songs result in emotional stimulation. Perhaps our ability to derive the emotions of other people through the tone of language which they use, is mimicked in music, and this also produces an emotional response. We could speculate that we find rhythms contained within music to be so encapsulating, because of the motor control that we have evolved to help us perform other tasks, such as running or the use of tools like a knife to chop up food. It is hard to deny though, that this explanation is still rather unsatisfactory. It does not quite do justice to the sheer power that certain Beethoven symphonies or Bach fugues possess. However, this is the only rational explanation that we currently have, without us introducing the concept of god or divine influence. It seems difficult to argue that our love of music is evolved, if even a byproduct of that process.
Many composers wrote their music ‘soli deo gloria’ (for the glory of god alone), including Bach and Handel. It is perhaps notable that they thought this, but what is more interesting is the recent obsession that humans have had with god, or some greater power, over the last few millennia. It is an idea that has arisen in many different cultures, from the polytheistic beliefs of the Greeks and Romans, to the monotheistic beliefs of the three Abrahamic religions. Since it is only in the last few hundred years that these beliefs have started to be challenged, the question must of be asked of whether the psychological trait of believing in a higher power is an evolved one, and therefore if it gave us a selective advantage.
We would expect evolution to lead to adaptations that give us a greater understanding of the world around us, so that we can manipulate our environment to give us the greatest chances of survival and reproduction, so indeed at first it does seem counterintuitive that belief in something supernatural that cannot be seen or heard