By Daniel Tarade
The theory of evolution has had a controversial history. At its simplest, any theory of evolution holds that species are mutable, subject to change. Yet, when people think of evolution, what comes to mind is Darwinism. That forces of natural selection act upon individuals of a species, with the weak killed and the strong spared. Over time, species become more fit and increasingly adapted to their environment. So, it may come as a surprise that some view natural selection and adaption as only a minor factor during evolution. In fact, a major camp of biologists now see that random drift is the most significant driver of evolution. Why do I think it is important to clarify the agents of evolution? It is not simply about being more correct. Our models of evolution not only influence our thoughts on ecology but also impact our conscious and unconscious thoughts on humankind. Our entire outlook on economics and race and justice passes through the filter of ‘survival of the fittest.’ Recognizing the important role of chance in the ‘natural’ world can help undermine the damaging ideology of competitive capitalism.
How does natural selection work? As written by Darwin, heritable and natural variation exists in every population. With breakthroughs in molecular biology, we now understand that genes, encoded by DNA, are the units of heritability. Mutations occur in DNA at a low, background rate that is increased by exposure to mutagens, like radiation. From an adaptationalist point-of-view, some members of a species are more ‘fit.’ Quite simply, fitness refers to the ability of an individual to pass on their genes. A ‘fit’ individual might be better at finding food (and thus lives longer due to better nourishment) or more capable of attracting a mate (higher chance of having offspring). These fit members of a species are more likely to procreate and, over time, the species as a whole becomes more fit as genes variants that lower fitness are eliminated. One important consideration is that there is not objective fitness. Rather, relative fitness changes with the environment. Take the peppered moth. One of the most famous examples of natural selection, the peppered moth can be either white (typica) or black (melanic). Before the industrial evolution, the aptly-named typica variety was the most prevalent in the UK. As soot was released in massive quantities, the environment quite literally blackened, making the melanic individuals more camouflaged to birds and, therefore, more fit. In a short amount of time, the melanic variety went from being few and far between to the most common. It is remarkable that, as pollution decreased, the typica variety of peppered moth has reasserted its dominance, with melanic individuals vanishing. In the largest study of its kind, a scientist released thousands of typica and melanic peppered moths in small batches over six years.[i] They found that, on any given day, the melanic moths were 10% more likely to be eaten. This is textbook Dawinism. Other examples exist and can be measured in real-time. The beaks of certain birds (UK Great Tit) have been getting longer. This has been attributed to the increased usage of bird feeders, where a longer beak allows greater access to the food. Similarly, The Beak of the Finch (amazing book on adaption) describes sophisticated studies on the Galapagos island with Darwin’s finches (specifically ground finches). The wife and husband duo, Rosemary and Peter Grant, have shown that as food availability changes, different selective pressure emerge. In drought years, where smaller seeds become scarce, ground finches with larger beaks were more likely to survive because they can crack larger nuts. These are all example of natural selection and ‘survival of the fittest.’
What is ‘survival of the fittest’ not? Well, it’s not the creation of the fittest. In all three described examples (moths, tits, and finches), it is not as if a self-reflective genetic code conjured new morphological features out of thin air. Rather, variation exists naturally within the population, whether it be different colour or different beak shape. If a specific feature confers increase fitness upon an individual, it would be more likely to survive and propagate. Over a few generations, changes at the population level can become evident. That is how we get headlines like, "British birds adapt their beaks to birdfeeders.” It is not the case that a congress of birds carried a motion to elongate their beaks. Rather, adaptive evolution occurred at the population level, not at the level of the individual. In short, birds with shorter beaks were less likely to reproduce.
‘Survival of the fitness’ is also not finished. What these studies show is that natural selection is an ongoing process. As environmental conditions change, different traits become desirable or expendable. As a corollary, no species is static or ideally adapted. Everything exists in flux. As Bob Dylan wrote,
The line it is drawn
The curse it is cast
The slow one now
Will later be fast
As the present now
Will later be past
The order is
And the first one now
Will later be last
For the times they are a-changin'
All of this is to clarify what scientists mean when they discuss natural selection and adaptation. But is ‘survival of the fittest’ the most important means of evolution? Or is it possible that the organization of our own societies have influenced the lens through which biologists view evolution? It may come as a surprise that there is fierce debate between neo-Darwinists and those who instead describe evolution as compelled by random drift. Since the 1960s, war has waged. In defiance of adaptationalist views on evolution, a camp of biologists have touted the neutral (or its close relative, near-neutral) theory of evolution. This group of scientists state that most genetic variation comes from random mutations that are neither beneficial or deleterious. And it’s true. Many DNA alternations have little to no impact on fitness one way or another. They just exist. In finite populations (i.e. all of them), neutral mutations will either become fixed (found in all individuals) or go extinct due to simply sampling error from generation to generation. Further, computational modelling has found that, in small populations, even mutations that are slightly deleterious are not purged by natural selection. Put in other words, it is not always the case that a genetic feature is present because it is adaptive. Rather, advocates of the (nearly) neutral theory of evolution espouse that evolution is more a case of what can be tolerated rather than what is adaptive.
With this in mind, the lengths some evolutionary biologists go to describe certain features as adaptive is maddening. Neo-darwinian thought occupies a Panglossian landscape - the best of all possible worlds. From their perspective, natural selection is an omniscient and omnipresent machine that has crafted only the finest of specimens. It is why some scientists have tried to describe severe mental illness as adaptive in some way.[ii] If 1 in 25 people have schizophrenia, bipolar disorder, or some other severe mental illness, it must be because the underlying genetic variation is (or can be) adaptive. This thinking is harmful in that it naturalizes all sorts of ails and injustices. Neutral drift and the polygenetic basis for many complex phenotypes (like brain functioning) does a much better job of explaining the presence of certain mental and physical disabilities.
And there are tonnes of other, more innocuous, examples of neutral drift. For example, the prevalence of read hair in Ireland is thought to have arisen from genetic drift. Another example is vestigiality. The remnants of once useful organs and body parts are replete on our planet. When a feature is no longer beneficial, mutations that affect that feature are less likely to be harmful. That is why humans have the remnants of a tail and whales have bits of pelvis. Vestigial features do not arise from natural selection but its absence. Similarly, essentiality of nutrients differ among different species. If an animal’s diet is rich in vitamin C, the gene that allows for de novo synthesis of vitamin C can be (and is often) lost due to random drift.[iii] Not because vitamin C essentiality is adaptive but because it is tolerable. And if human diet is devoid is vitamin C (like in early seafaring days), people get scurvy and die. No human can make their own vitamin C, so natural selection is unable to select for fit sailors who are able to survive a diet lacking fresh food. We are fixed. This is neutral drift. Another poignant example of neutral drift, at a molecular level, is the coelacanth. Long thought extinct, the rediscovery of this lobe-finned fish that appeared unchanged from the fossil record (dating back 400 million years) seemed to affirm natural selection. Much like sharks, these creatures are held up as perfectly adapted. However, genomic analysis of the coelacanth has shown significant molecular evolution, particularly in DNA that does not encode proteins.[iv] It’s just drift.
I do not want to fixate on the evidence for the two theories. I want to highlight how political ideologies influence biological theories and vice versa. One of Darwin’s biggest inspirations was Adam Smith, writer of The Wealth of Nations. Adam Smith wrote about how division of labour allows for efficiency and that private businesses will emerge and go bankrupt in response to shifting demand. Selective pressure refines both the business and the individual, writes the adaptationalist Adam Darwin. On his voyage to the jungles in South America, Darwin said that “the advantage of diversification in the inhabitants of the same region is, in fact, the same as that of the physiological division of labor in the organs of the same individual body.” When combined with Adam Smith and his laissez faire capitalism, you can see how inequality of wealth becomes normalized; those who are wealthy in our society are better adapted than those who are not. They deserve it more. The traits that lead to increased fitness can be intelligence, work ethic, courage, etc. And with a theory of natural selection, tied intimately to our genes, it becomes easy to argue that there ought to be a hierarchy in our society. It seems so…natural.
Since the industrial revolution, people have tried to justify economic injustice by appealing to natural selection. That slavery is not only acceptable but laudable because Africans are less intelligent and more malleable than white Europeans. Remember that racism was a post hoc justification for slavery spread by greedy people looking for profit and that scientists, with thoughts of natural selection running through their head, were co-opted in this process. If Sub-Saharan Africa had not yet to undergo an industrial revolution, they must be less adapted and their genes inferior. Slavery was never justifiable but we know now just how laughable it is for anyone to claim a genetic basis for racial superiority. Sampling a large number of polymorphic loci in the human genome can reliably segregate people based on geographic ancestry. However, race and geographic ancestry are not interchangeable, and most genetic differences are found within a race, not between races.[v] The term race has been used for the last several centuries to describe a homogenous group that is heterogeneous when compared to other groups. That simply does not bear out in population genetics. These ideas also ignore that an individual human is not predicated on the basis of genes but an interaction between genetics, environment, and chance. A historical evaluation of evolution strips away the veneer of objectivity appealed to by supporters of our current economic system. Inspiration for the idea of natural selection came from economic theory and economic practices are in turn supported by seemingly objective scientific theories.
Now try to imagine that the neutral theory evolution was the first to topple intelligent design, not natural selection. And that economists, trying to understand societal labour and organization, looked to biology for insight. What they might describe is that drift plays a big role in determining who ends up with a well-paying job or running a successful business. That, in a notable number of cases, people who are less qualified end up getting the job and creative, brilliant people struggle to make ends meet. Sure, natural selection may play a role. Absolutely horrible business ideas may be more likely to fail and ideas that address real needs may be more likely to succeed but this refinement of the economy is subsidiary to drift, to chance, to mere luck. Instead, adaptationalist ideology runs rampant and success is justified as arising from genius and hard work. People like Steve Jobs are deified while those who developed similar technologies earlier are hardly remembered. There is clearly a role for drift in business. And the same goes for the individual labourer. What is the difference between a person who ‘succeeds’ in life and the person who defaults on their mortgage? It’s luck when you happen to play the same sport as your boss and have the opportunity to forge a strong relationship. It’s luck when a friend knows of a job listing at a company that isn’t advertised publicly. It’s luck when a fellow job applicant has a flat tire and misses the interview. Thus, the proponent of neutral drift in evolution would be an advocate for equity in society. That we should not blame the individual for lacking food, water, and shelter. From this theory of evolution, more egalitarian societies would emerge. Conversely, ‘survival of the fittest’ glosses over the role of chance. Since natural selection focuses solely on genes, a person evaluating our economy as fair or unfair also ignores the role of education, poverty, nutrition, and violence. Most frightening, proponents of eugenics describe their work as artificial selection - a mere extension of natural selection. Instead of fighting for a world where everyone’s material needs are met, many in our society celebrate the death of those who are perceived to be maladapted. The drug addict, the welfare queen, the bum. For example, Darwin awards are ‘awarded’ to those who have died in stupid and idiotic accidents. In their death, they have ‘cleansed’ our gene pool. Yet, despite the scientific claims made by lay neo-Darwinists, the ideological basis for their view of the world lays just below the surface.
Humans are the conductors of science. In spite of that simple fact, science enthusiasts tout the process and outcome of science as objective. As undeniable and unwavering. Yet, multiple process drive evolution, and scientists cannot agree on which is more important. It is not incorrect to say the natural selection works on individuals within a population. It is also not wrong to state that random, nearly-neutral mutations accumulate and are fixed in a population. Simultaneously, species drift and evolve under the dual mandate of chance and ‘survival of the fittest.’ The intersection of ideology and science emerges when scientists design their experiments and interpret their results. Let me illustrate. Most variation exists within a race, not between races. Yet, one can identify the race of an unknown individual by analyzing thousands of polymorphic sites in the genome. These are apolitical statements. However, whether one interprets these results as supportive of the human conception of biological race depends on your ideological lens. I reject the concept of biological race in humans as it impedes unity among the labouring class. Darwinism and adaptationalist thought emerged from capitalist theory and in turn naturalizes human capitalism as a form of ‘survival of the fittest.’ So, it is important that we remember that capitalism is not natural in any way. That we are not simply the product of our genes. That our environment influences our economic success. That randomness plays a role in both ecosystems and our human systems. The simplest ideology I possess is that maximizing human pleasure and minimizing human suffering is good. At this, capitalism fails.
First, I would like to highlight the influence of Richard C. Lewontin on shaping this post. I have been reading a collection of lectures he wrote entitled “Biology as Ideology.” Lewontin is also a pioneer of the neutral drift theory of evolution.
As mentioned, the evolution of vitamin C essentiality is a great example of neutral drift. A random assortment of mammals have lost the ability to synthesize vitamin C (at least three times in the mammalian lineage; bats, guinea pigs, monkeys). Interestingly, some bats have regained the ability to synthesize vitamin C but this has not been associated with any benefit. Indeed, among very closely related bats that consume similar foods, some lack the ability to synthesize vitamin and others have regained the ability. The vitamin C essentiality in guinea pigs (not seen in other rodents) was also serendipitous. In the 1700s, the British navy began using citrus fruit to treat scurvy. However, the cure was lost in the mid 1800s as a switch from fresh lemons (more vitamin C) to lime juice stored in copper tanks (less vitamin C) made murky the idea of a simple cure for scurvy. Researchers trying to study a different disease of vitamin deficiency chose the guinea pig as an animal model. In trying to induce beriberi (deficiency of vitamin B1), the guinea pigs instead developed scurvy. By finding foods that could prevent scurvy, it became possible to isolate vitamin C in 1932.
[i] Cook, L. M., Grant, B. S., Saccheri, I. J., & Mallet, J. (2012). Selective bird predation on the peppered moth: the last experiment of Michael Majerus. Biology Letters, 8(4), 609-612.
[ii] Keller, M. C., & Miller, G. (2006). Resolving the paradox of common, harmful, heritable mental disorders: which evolutionary genetic models work best?. Behavioral and brain sciences, 29(4), 385-404.
[iii] Drouin, G., Godin, J. R., & Pagé, B. (2011). The genetics of vitamin C loss in vertebrates. Current genomics, 12(5), 371-378.
[iv] Amemiya, C. T., Alföldi, J., Lee, A. P., Fan, S., Philippe, H., MacCallum, I., ... & Organ, C. (2013). The African coelacanth genome provides insights into tetrapod evolution. Nature, 496(7445), 311.
[v] Witherspoon, D. J., Wooding, S., Rogers, A. R., Marchani, E. E., Watkins, W. S., Batzer, M. A., & Jorde, L. B. (2007). Genetic similarities within and between human populations. Genetics, 176(1), 351-359.