The Selfish Gene: Chapter 3 Summary & Analysis

Dawkins thinks that humans are survival machines, and so are all other living entities on the planet as well, including “animals, plants, bacteria, and viruses.” On the outside, it seems like these organisms are all very different. But on the inside, the base chemistry of every living thing is the same: they all contain replicators (genes, or DNA) that are more or less the same type of molecule. This molecule is shaped like a double helix (or coil), and is made up of four kinds of building blocks (called A, T, G, and C). The only thing that’s different, between a man, another man, a snail, an octopus, an oak tree, and a fish is the order (or “sequence”) of their genetic building blocks.

Every cell of a body contains a copy of its DNA. DNA is a set of instructions (or “architect’s plans”) for how to build a body. Dawkins thinks it’s similar to imagining a building with a bookcase in each room containing the architect’s plans for that building. The bookcase is a “cell,” and it contains lots of binders full of loose pages. The binders are “chromosomes.” A human bookcase has 46 binders, and each page in each binder is a “gene.” The only difference with the metaphor is that there is no actual “architect” in the case of DNA. The DNA instructions wound up that way because of natural selection. 

Architect’s plans have binders full of pages that come from people’s mothers and fathers. One’s mother’s sixth page of her third binder might say “build blue eyes,” and one’s father’s might say “build brown eyes.” One of those pages will end up in one’s own binder. Each sperm from one’s father contains 23 “binders.” When the sperm meets the egg (which also contains 23 binders), the pages from both sets of “binders” will be all mixed up and reorganized to create the set of binders that become the blueprints for oneself. They’ll be so mixed up, in fact, that it’s nearly impossible to figure out which exact page came from which parent. Genes are essentially shuffling around from body to body this way forever. 

The actual picture is more complicated. Technically, a gene isn’t an exact “page” but a bit of information that might be a sentence long, half a page long, or three pages long. It might even be split up across several pages out of order. Dawkins thinks it’s unnecessary to worry about this though, as he’s just using “gene” to mean any bit of chromosome that contains instructions that can be passed on intact (however long, short, or mixed-up the instructions are).

Dawkins now explains how natural selection comes into the picture. Remember that genes are all copies of each other. Sometimes, there’ll be a copying mistake, say, one letter on one page is copied incorrectly. This is called a “point mutation.” Sometimes, the order will be wrong (it will be spelled backwards, for example). This is called an “inversion.” Sometimes, by accident, the different order connects bits of genetic material that actually work better together. Externally, this means the body that’s built will be slightly different. Internally, it means the new sequence will stick together more tightly and pass on in that new order instead. 

Dawkins thinks that, because this is how natural selection works, the “thing” that is evolving must exist in lots of copies that can stay intact for long periods of evolutionary time. Genes have these characteristics. But individuals and species don’t. This also means that, technically, the gene is immortal. It lives on in copies or clones of itself, potentially forever (if it’s not miscopied). Genes are immortal coils of DNA. Individuals, then, are like temporary colonies or federations of genes that wind up living in the same body before they build a new one to move into.

A “good” gene will live longer if it makes a better survival machine to live in. For example, a gene that instructs its survival machine to have longer legs (to escape fast predators more quickly) will live longer in an environment where there are fast predators. This means that at the genetic level, the gene is always “selfish,” because genes that act in ways that preserve their existence win out in natural selection.

Of course, genes also cooperate since they share survival machines. Dawkins uses another metaphor to explain this phenomenon: oarsmen in a rowboat. An oarsman cannot win a race by himself. He needs several colleagues to fill up the boat, each in a different position on the boat, and each with a slightly different skill set. The coach decides which people to put together by shuffling the potential oarsmen into teams and seeing which combination performs better together. The oarsmen are the genes, and they are competing for seats on the boat. Each oarsman is selfish: he wants to win the race. But he also needs to work well with his teammates to do so. So, an oarsman who’s good at what he does and works well with other oarsmen will tend to be picked for the team.

Dawkins wonders why genes build survival machines that reproduce instead of just building bodies that last forever. He thinks that this is because evolution isn’t perfect. Some “bad” genes slip through the cracks. There are likely late onset “lethal” genes that become activated in old age (say, a gene for “senile decay”). Because they don’t cause the death of their survival machines before reproduction, they’ll be more successful at slipping through undetected, which explains why they still exist, and why humans die.

There’s also another puzzle to think about. If genes are the things evolving, why do they build survival machines that reproduce and only pass on half their genes to the next generation? Dawkins thinks that’s because colonies of genes don’t care about staying together. There must be some evolutionary advantage to building a new body through reproduction, and likely the gene responsible isn’t concerned with the survival of other genes. It’s only concerned with its own survival. So, the gene cooperates with whichever other genes are necessary for it to keep replicating, regardless of which survival machine they come from.