‘Evolution’ is not the name of a specific process, as for example ‘fermentation’ is, nor is it an abstract process that has realisations in a number of different contexts, as for example ‘compilation’ (of machine code) is. It’s a place-holder for a process or event: when the DNA of a species changes - without at the same time changing it into a different species - ‘evolution’ tell us to look for a change in the circumstances of that species that caused or facilitated that change. It tells us to look for a natural cause rather than magic. It does allow limited magic, in the form of DNA damage, combination or random mutation.
‘Evolution’ does not ‘cause’ anything to happen. Rather, ‘something’ causes a species’ DNA to change and that ‘something’ is gathered with all the other ‘somethings’ under the heading of ‘evolution’. This is why the only people who argue with ‘evolution’ have world-views that depend on creationism. They want us to look for God(s) as an explanation of the natural world, and Darwin wanted us to look for the natural world to explain the natural world.
When Darwin proposed looking for natural rather than magical explanations, he had no idea about DNA and its attendant chemistry and engineering. Mendel suggested genes about forty years later, and Crick and Watson discovered the structure of DNA almost a hundred years later, and it would take them a further decade to work out the roles of RNA, mRNA and how the gene makes chemicals in the cell. It was about forty years later, that a number of people suggested that genes could undergo short-term localised changes that do not affect the DNA sequence, in response to the environment of their carrier phenotype, which we now know as epigentics.
We can’t blame Darwin and his successors for putting forward some fairly ropey suggestions about how species change. We can blame their pop-culture successors for continuing to promote those ropey ideas. Anyone in academe still talking about sexual selection as an evolutionary mechanism is looking for book sales, not answers. Why?
Evolutionary ‘fitness’ is measured by the proportion of future generations that carry the animal’s genes. It follows from this that the evolutionary fitness of an individual cannot be known at the time of mating, but only by some future biologist. This is as it should be: nobody knows if the environment might change sometime in the future to favour traits currently hanging on by the skin of their teeth. Predicting evolutionary fitness means predicting the future. However, we can make some limit-case observations. Individuals who die without offspring have an evolutionary fitness of zero. In a settlement of N people, an individual’s evolutionary fitness is approximately n/N where n is the number of children they have. It’s fairly easy to see where that goes: if the settlement is the planet, the evolutionary fitness of an individual is vanishingly small. We can measure the fitness of a trait or gene in the same way, and that will achieve higher measures.
Because evolutionary fitness cannot be known at the time of reproduction, and is anyway vanishingly small for individuals, means that the pop-culture idea of the female somehow choosing a ‘fit’ mate is more or less nonsense. There are no ‘fit mates’. There are ‘fit traits’, but for reasons that defy understanding, looking like Ryan Gosling or Eva Mendes don’t seem to be amongst them. Culture and evolution are orthogonal (sigh).
I’m going to need to spend more time on sexual selection than it really deserves, because it’s one of those ideas that really appeals to people, and it sticks in the mind like a burr.
Sexual selection is not females somehow divining the quality of their mate’s genes and his willingness to hang around post-coitus to provide for the offspring. She can’t do that because she can’t predict the future. At the very most she can choose by analogy with other couples who seem to be successful at the moment, but the she doesn’t know if they are going to continue to be successful. Partnerships are like any other investment: past performance is no guarantee of future results. Sexual selection is the selection of any other trait that hitch-hikes with traits that make the male attractive to the female. She chooses on the basis of the man’s attractiveness, and takes her chances about what else follows. The idea that attractiveness is itself a fitness trait, because attractive people have more surviving children, has only gained popularity since the mid 1960’s, which by no coincidence, is when the so-called Sexual Revolution started. It’s retro-fitting the ideas to women’s contemporary sexual behaviour. Previous descriptions were there to valorise the social role women were supposed to be playing.
First, smart, pretty people tend to have fewer or no children or to stay single: they have the options, and they have the intellectual resources to enjoy the culture of their time. Second, most women think, according to the surveys, that only twenty per cent of men are ‘above average’ in looks. So how is it that far more than twenty per cent of men have children? Clearly there’s a disconnect between inter-subjectively-agreed attractiveness and who a woman is prepared to get pregnant by. Third, the only way to save the hypothesis is to make the idea of ‘attractive’ hopelessly subjective, contextual and contingent, and therefore so obviously un-linked with actual evolutionary fitness, that the whole thing falls apart.
If ‘spreading success by selection’ does not work, what does? ‘Restricting failure’. As an example, by now the syphilis bacteria should by now have evolved to deal with penicillin, since many other bacteria have turned into ‘superbugs’ in a much shorter time, but it hasn’t. Superbugs arise because some had anti-biotic resistance and some did not. The ones that didn’t were wiped out, leaving the ones with the resistance to breed. Syphilis bacteria seem not to have any variants in its population which are resistant to penicillin.
Eagles who didn’t build their nests in inaccessible places and spent most of the day soaring would have lost their young more or less immediately. The only eagles left after a few years of that would be the ones whose genetics disposed them to build their nests half-way up a cliff. In another example, the birds of a given species don’t develop harder beaks when the supply of softer seeds runs out: instead, there was intra-species variation for beak shape and hardness. The birds with soft beaks starved, as did their offspring, and the birds with harder beaks don’t starve, and their offspring live. The birds don’t need to kill anybody, or deny them access to resources. Nature did that all by itself.
In people, a characteristic lasts because someone is willing to breed with a carrier. Socially dysfunctional behaviour can survive, passed down the generations by example, genes, and culture, as long as someone can be found to breed with the person behaving like that. Otherwise the human race would have bred out drunks, shrews, addicts, borderlines, anti-socials, and all sorts of other problem-people, well before the Greeks developed psychology to name the problems. But no. All those dodgy traits were kept going by men who just couldn’t keep their dicks out of crazy, and by women who just couldn’t say no to Bad Boys. The human race has not wiped out one dysfunctional psychological trait, or one physical malformation or dysmorphism, by breeding it out. What it did do was develop an understanding of diet and medicine. That’s why the WHO eliminated smallpox in a generation. Cluster B disorders, which are defined by specific behaviours and show a high heritability could be bred out in a couple of generations, if men knew how to identify the behaviours and refused to mate with anyone who showed the behaviour. Hasn’t happened yet.
Cultural skills are mostly learned, and at a high cost of time and effort, and there is very little correlation between genetics and, say, virtuoso tenor saxophone playing, the thousands of hours of playing needed to achieve those levels of virtuosity, and the personal characteristics needed to put in that effort. There is of course a genetic influence on being a virtuoso tenor sax player. Playing a musical instrument often is a mood-altering activity and the ability of the player’s body (the brain is part of the body) to enter one of the moods needed to play for extended periods of time will be dependent on the release and re-uptake of one or more hormones: that is genetic in the first instance and then a result of use. Not being tone-deaf, and to be able to sense rhythm, these are to some extent genetic, though given the basics, a lot can be learned.
Because cultural features are not linked to DNA, evolutionary processes cannot remove tenor saxophonists from the world. Violence could remove the saxophonists, and legislation could prohibit the manufacture, ownership or playing of a tenor sax, but that’s not evolution because there’s no gene being changed or eliminated. Oddly, if there was a tenor-sax-playing gene, and the human race decided to kill its present carriers, that would be evolution. It would be genocide and a crime as well, and it would count as a sorry moment in human evolution. Evolution is not progress, it’s simply change.
There was a brief period when people thought there would a gene for everything, but that search has been fruitless, except for a handful of rare diseases. It seems that many features of the phenotype can be produced by a number of different combinations of genes, or that external stimulus is needed as well as the presence of genes. Making a male, after all, requires X and Y chromosomes, an SRY gene to trigger the production of testes, the testes to produce testosterone and other androgens, and an androgen receptor. Any of that goes wrong, you don’t get a boy, you get a girl with maybe some bits missing. Genes are not one-one mapped to human behaviours. Mostly there’s no mapping at all.
All this is bad news for the evo-psycho crowd. Because genes don’t produce the details of a given culture, it turns out that almost nothing about human culture has anything to do with evolution. Because sexual selection has no correlation with evolutionary advantage, contemporary human behaviour is not the result of thousands of years of evolutionary fine-tuning. There is no evolutionary rationale for your neighbour’s cockolding wife: she has no idea whether the Bad Boy impregnating her has more dominant genes than her faithful provider Beta husband. That’s just evo-porn for the masses. ‘Strategies’ such as hypergamy, cuckolding, testing for social dominance and all the rest may be good strategies for determining present advantage, but have no evolutionary efficacy beyond chance. DNA doesn’t work like that.
No comments:
Post a Comment