In Chapter 3, Dawkins breaks down the divisions between living beings, claiming they are just different survival shells for the same replicators, DNA. The DNA is present in each cell, described by Dawkins as a bookcase in each room containing the architects plans on how to build the house. Each “bookcase” or DNA contains “binders” or chromosomes with “loose pages” or genes in each binder. As you can see, Dawkins really likes his metaphors. This metaphor, however, falls apart in that there isn’t an architect that wrote the plan on how to build the house. It got there by natural selection. Sometimes, when the pages are being replicated, mistakes are made and a new sequence results. For the body, this means that it will be built a bit different in the future. For the genes, it means that, due to natural selection and something called linkage disequilibrium, this sequence will stick together more tightly and these “pages” will be passed on together. In Dawkins opinion, this means that the smallest unit natural selection acts on is genes, thereby making it the unit of selection. A gene can live forever by replicating itself and being passed on to new survival shells, while the shells, or organisms, cannot. However, it is in the genes best interest to build a good survival shell that can live and pass on the genes.
Because genes share survival shells, they share the same fate. Therefore, they help each other. This is not altruism, because they do not decrease their own chance of survival to help others, but instead increase both of their chances of survival by working together to create a great shell. They don’t care about each other, which is why they don’t care if they get mixed up or separated when they are passed on. At this point, Dawkins does ponder why the genes don’t just build one great machine that lasts forever instead of bodies that need to pass on the genes so that genes can live forever. He attributes this to a mistake. Evolution does not build towards perfection but instead towards the best available form. “Bad” genes always slip through to ruin a great machine. The best bad genes are the ones that are only lethal at old age, because they let the machine reproduce and pass them on before they kill the shell. And that’s Dawkins on aging.