A Gene Centered View of Natural Selection

Natural selection was Darwin’s term for the mechanism of evolution. In the slow process of evolution nature selects which organisms adapt to their environments successfully (that are most successful at surviving and reproducing). But what is the unit of selection? Is it the species, group, individual or gene? At what level do natural environments shape the evolution of life? Could there be a blending of different units or is one dominant? For example, do species evolve as a consequence of group selection, or do groups evolve as a result of individual selection; or do genes ultimate control the process?

Richard DawkinsThese questions have been debated by biologists and academics for a long time. Richard Dawkins, with the publication of The Selfish Gene, sided on the gene centered camp. The idea of gene selection had been proposed in scientific papers: First by Bill Hamilton in 1964 and then by others, such as John Maynard Smith and Robert Trivers in the early seventies.

Published in 1976, The Selfish Gene placed gene selection into the public sphere by getting beyond the technical aspects of the scientific papers. Dawkins’ book was accessible to a general audience, and has been influential in shaping evolutionary thinking (the 30th anniversary edition was published in 2006). It was, however, controversial as much for its implications as for the gene centered view it supported. According to Dawkins, the book was misinterpreted and used by some groups as biological justification for selfishness in humans; but his intention was to explain how natural selection works, not how people should behave. Dawkins clearly points this out in the first chapter of the book:

“I am not advocating a morality based on evolution. I am saying how things have evolved. I am not saying how we humans morally ought to behave.”

The Metaphor

The title, The Selfish Gene, is a metaphor for how genes propagate. By controlling the traits of organisms, genes influence their own survival. The genes that aid in survival and reproduction are more likely to be copied in future generations. In that sense the genes are selfish and potentially immortal (in the form of replicas), while the bodies that contain them are mortal. Dawkins writes:

“Individuals are not stable things, they are fleeting. Chromosomes too are shuffled into oblivion, like hands of cards soon after they are dealt. But the cards themselves survive the shuffling. The cards are the genes…They are the replicators and we are their survival machines. When we have served our purpose we are cast aside.

genesThe selfish gene metaphor, though powerful, has its limitations; a single gene can’t do very much. Genes interact with each other and combine in complex ways to give rise to physical traits. It is essentially groups of genes that survive (genes that work well together). Therefore, a successful gene can be defined as a portion of genetic material that survives through a number of successive generations.

 Explaining Altruism

“Survival of the fittest,” that is the popular catchphrase for evolution. But an analysis of the mechanisms of evolution requires that we ask: the fittest what? For Darwin, it was the fittest individual that would survive and reproduce. In the middle of the 21rst century, biologists were reintroducing and debating Darwinian ideas. Group selection (the idea that the fittest groups would survive) was gaining popularity. The propagation of the species was the consequence of the fittest groups. However, some biologists were pointing out that group selection was inadequate to explain altruism in animals.

Altruistic Behavior in  Animals

Dawkins is a zoologist by training, and The Selfish Gene focuses mainly on the role of genes in animal behavior. He analyses animal behavior in a variety of species, and points out the correlation between altruistic behavior and relatedness. In other words, the closer the relationship (in terms of shared genes) the more altruism we can expect to see. In this view the genes are at the core of the altruistic behavior, as they aid in the survival of copies of themselves.

zebrasWhen an animal acts altruistically, it appears that the animal is sacrificing some survival need in order to increase the chance another will survive. It does not matter how small the sacrifice is, because a number of small sacrifices can accumulate over time, and also can be reciprocated. The group selection hypothesis interprets altruism as benefiting the group, and in the long run, these groups will be more successful. However, others claimed that selfish individuals would undermine the altruistic group. The selfish individuals within the group would exploit the altruistic system, eventually winning out. The struggle for existence would favor the selfish individuals over the altruistic individuals.

Dawkins argues that seemingly altruistic behaviors can be interpreted differently from a gene centered view. From the gene point of view, the act is still selfish because it aids exact copies of itself (in the form of children, siblings, cousins and so one). Animals are sometimes altruistic because they are programed by their genes to be so. Whether to be selfish or altruistic is a delicate balancing act that is ultimately guided by the genes chances of survival. In addition to helping close relatives, individuals are also dependent on groups. Therefore some consideration for the well-being of the group would likely come into play.

The Social Insects

Perhaps no other example of altruism in animals is as evident as in social insects. This is probably the best example of which a gene centered view of natural selection is adequate. Honey bees, wasps, ants and termites are familiar social insects, and they live in large colonies. The colony functions as a highly organized unit, where each individual has a specific role. Although the roles vary, they can be broken down into two main categories: Carers and bearers. The carers are sterile workers; the bearers are the reproductive females (queens) and reproductive males (drones or kings).

In most species each individual shares in the caring and bearing roles (not necessarily equally). But with social insects it is clearly divided. The sterile workers will devote their lives to providing and protecting the reproducers, even to the point of suicidal actions. This is what we observe when a bee stings a perceived threat to the hive. The bee will almost certainly die.

With an individual selection view, we would not expect suicidal behavior to evolve, because there is nothing to gain for the individual. However, the fact that the workers cannot bear offspring of their own, self-sacrifice for the good of the colony aids in the survival of their genes (shared genes with the reproductive members of the colony). From the gene centered view, what really matters is not just reproducing offspring, but assisting the survival of one’s own genes. There are many strategies in which this can occur (usually a balance of risk and reward). The triggers for the behaviors are surely subconscious. You could say they are controlled by the genes, or call it instincts.

Are Genes Really in Control?

Although there are mountains of evidence that shows life does evolves, determining the level of selection is tricky; it seems like a matter of interpretation. It is not hard to see how each unit of selection would naturally influence the others in the same way (either positively or negatively). For example, if the fittest individual is selected, it will aid its group, species and genes to propagate. We could change the last sentence by randomly shuffling the units (individual, group, species and genes) and it would still hold true.

Maybe natural selection is a complicated process that includes several units of selection. Species, groups, individuals and genes are likely interconnected in ways that are difficult to quantify. I suspect that this issue is not completely resolved among scientists. Nevertheless, I find that the gene centered view is both fascinating and compelling. It is a somewhat counter-intuitive way of looking at evolution, and yet upon closer examination it makes so much sense. Logically, it all hangs together.

 

References: Richard Dawkins, The Selfish Gene (Oxford: Oxford University Press, 30th anniversary edition, 2006).

Beautiful Minds: Richard Dawkins, Published on April 25, 2012. BBC4 https://www.youtube.com/watch?v=C2I8f4lpBLU


 

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