The Selfish Gene summary

Evolution occurs through differential survival: in a given population of entities with differing abilities, some survive and propagate while others die out.

But contrary to what is often thought, the basic units that evolution acts on are not individual organisms but genes: short snippets of DNA, the replicator molecule that is the basis of all life on Earth.

A gene is ‘selfish’: it acts in a way that promotes its own survival at the expense of other competing entities. However, genes themselves have no conscious motives; it is simply their behavior that we can describe as seemingly selfish. Similarly, while the process of evolution could appear to be motivated towards creating entities that are suited to particular environments, it is not consciously trying to achieve this.

To understand why genes seem selfish, we must examine the physical environment they exist in: Genes come in packages called chromosomes, which are sheltered within the cells that make up an organism. Chromosomes come in pairs: humans have 23 pairs (46 chromosomes in total). Both chromosomes in a pair have the same organizational structure, so if an area on one chromosome houses the gene for eye color, then the other chromosome will have a gene for eye color in the same location. However, the versions of these genes may not be the same: one might be for blue eyes and the other for brown. Different versions of genes for the same characteristic are called alleles; for example, there are several alleles of the eye-color gene.

Physically, all genes are fairly similar: they are all snippets of DNA. Where they differ is the information they encode.

DNA is basically a long molecular chain constructed of four types of molecules denoted by the letters A, T, C and G. Just as every word in the English language can be constructed from the 26 letters in the alphabet, these four basic building blocks can be combined into so many different and elaborate DNA sequences as to describe every feature of an organism.

Good camouflage for a tiger is very bad camouflage for a polar bear, because of the fundamentally different environments. A gene for tiger camouflage would have minimal chances of surviving in an icy environment.

Genes are not just affected by their physical environment but also by the genes around them: all the variations (alleles) of a species’ genes in the same gene pool. This includes both the specialized genes that only certain species have, like genes for building wings or carnivorous teeth, and the shared genes that different species have in common.

A gene affects a characteristic of the organism it belongs to – e.g. its speed, strength or camouflage. When this effect is advantageous, the organism is more likely to produce offspring that carry copies of the gene, and thus the gene survives.

However, one gene alone can’t build an organism. It requires tens of thousands of genes all working together to construct something as complex as a human body. But if genes are fundamentally selfish, then why would they cooperate in this manner?

It can take generations for one gene’s phenotype – for example, longer legs – to prove more successful than another. However, to survive, the bodies that genes build need to be able to react much faster to environmental stimuli – to eat, fight or flee in mere seconds. To facilitate this, genes build brains that allow organisms to respond to rapidly changing factors in their environment. We call these reactions “behavior.”

The natural environment can present an infinite number of different situations, so there is no way for an organism to have a prepared response to each one. Instead, behavioral responses are guided by ‘rules,’ which are encoded by the genes in a way that is analogous to how a computer is programmed. For example, two such rules could be for an organism to regard sweet-tasting things as rewarding and to repeat actions that lead to this reward.

Members of the same species are in direct competition with each other for resources, which can be expected to lead to confrontations between individuals. These confrontations can be dealt with via different behavioral strategies, ranging from fleeing to fighting to the death.

Behavioral strategies, like any other characteristic of an organism, can be expected to vary, and some are going to be better for the survival of the organism – and its genes – than others. In the same way that the success of a gene is determined by its environment, the success of an organism’s behavioral strategy is determined by how all the other organisms around it behave.

As pointed out earlier, because genes control behavior, and genes are selfish, then we can expect organisms within a group to behave selfishly toward each other.

However, there are many examples of behaviors in nature that appear altruistic, not least of which are the many examples of extremely devoted parental care, such as a mother bird feigning a broken wing to lead a fox away from her young. Altruism here can be defined as behaving in a way that reduces one’s own chances of survival for another’s benefit.

When characterizing interactions between organisms, a useful principle is the idea of the zero-sum or non-zero-sum ‘game.’ Basically, a zero-sum situation is one where one side wins and the other loses; for example, in the case of a cheetah chasing an antelope, either the antelope dies or the cheetah starves.

In contrast, a non-zero-sum game is one where both ‘sides’ are playing against a ‘bank’ that holds the resources. One player winning does not mean the other has to lose. The players can stab each other in the back to gain a bigger share of the bank’s resources, but, depending on the rules, they can also cooperate to outwit it.

One of the most distinctive traits of humans is culture: the aspects of our lives that are neither instinctive nor purely have to do with survival, for example, language, dress, diet, ceremonies, customs and art. Although basic human psychology and interests can probably be traced to the survival benefits of mutual altruism and aiding kin, these aren’t enough to explain the complexity and variety of culture.

Instead, culture can be considered the equivalent of a gene pool, with the basic unit of cultural evolution being a meme instead of a gene. A meme is the smallest piece of culture with potential immortality, for example, a tune, an idea or a YouTube clip of a dancing cat. The methods of transmission are the methods of human communication: speech, writing, the Internet.

Models of behavioral strategies show that populations tend to end up with a stable strategy, and that populations engaging in a mutually altruistic strategy tend to do well, even though each individual is motivated by the best interests of their genes.

But in some cases an even more optimal solution for all can be reached by forgoing the immediate survival interests of the genes. Consider a population in which there are two species with two different confrontation strategies: the Hawks, who always attack in confrontations and will fight until death or serious injury; and the Doves, who run away if attacked. Hawks will always win against individual Doves, but in the long run their strategy is actually less beneficial due to the injuries they sustain from fighting other Hawks. The solution that most benefits all the individuals is the ‘conspiracy of Doves,’ where all individuals in a population agree to be Doves, forgoing the short-term benefits of behaving like a Hawk in order to reap the long-term benefits of living peacefully and avoiding serious injury and death.