1. All living entities use DNA as their genetic code, and most also have similar fundamental chemistry.
2. DNA is a polymer of base units called nucleotides. All nucleotides have the same fundamental structure; they consist of a five carbon sugar called deoxyribose, a phosphate group, and one of four nitrogenous bases. The nitrogenous bases are abbreviated as A, T, G, and C. Variation in the nitrogenous-base order of DNA creates differences between individuals belonging to the same species and also differences between species. DNA is passed on from parent to offspring.
3. DNA is transcribed to RNA, which is then used by cells as a template for protein synthesis. The order of nucleotides in the DNA controls the order of nucleotides in the RNA, which in turn controls the sequence of amino acids in the protein. The proteins an organism synthesizes determine its structure and properties. DNA therefore controls an organism’s identity indirectly, using proteins as an intermediary.
4. The environment selects for the organisms whose phenotypes and behavioral patterns are best suited to that environment. Since phenotype is mainly determined by genotype, selecting for a well-adapted phenotype is usually equivalent to selecting for a well-adapted genotype. This is most obvious in cases where a gene directly controls a physical characteristic, for example fur color in mice. However, it also holds true in cases where a gene affects an organism’s survival more indirectly. For example, in a population of magpies, one allele of a certain gene might create a magpie that was better at learning from its surroundings. While the magpies with this allele would not directly pass down their additional knowledge to their offspring, they would pass on their ability to learn. If superior learning ability provided a reproductive advantage, the environment would still select for this allele.
5. Between organisms, genes compete. Within a single organism, however, genes must cooperate. A cancer cell is highly successful in the short term because of its high fecundity. In the long term, it is unsuccessful, because it destroys the body that had the potential to pass it on to offspring.
6. Simple nervous systems allow organisms to coordinate the timing of their movements and other behaviors. Complex nervous systems also carry out this function, but in a more complicated and sophisticated manner. For example, they process information from the senses and use it to send specific messages to muscles, instructing them how to react. Brains are also capable of memory; this allows them to send instructions based on information from long-ago experiences as well as those from the immediate past related by the senses. Nervous systems allow organisms to act with the appearance of purpose1. Complex nervous systems, if they are conscious, also make the organisms themselves mindful of a sense of purpose. In addition, brains simulate possible future situations. This predictive power is an advantage, because it allows organisms to avoid dangerous situations without actually having to try them once to see what will happen.2
7. The world is far too complex for most knowledge and most behavioral patterns to be hardwired by genes. Instead, our genes give us the ability to learn from the world around us. Some basic behaviors are explicitly coded by our genes, for example the instinct to withdraw one’s hand from a fire or parents’ instinct to care for their children. However, it would be hugely inefficient and ineffective if the only actions humans could perform were instinctive ones. Instinctive behaviors take a long time to evolve and generally are not very specific. “Avoid pain,” is broad enough to become an instinct, but rules such as, “Always turn the steering wheel left when parking uphill on a curb,” are likely too specific. Learning is a more efficient way to deal with the world, because it allows organisms to adjust to whatever circumstances they encounter, even when those circumstances are different from the ones in which they evolved.
8. Dawkins hypothesizes that consciousness “arises when the brain’s simulation of the world becomes so complete that it must include a model of itself.” In other words, when brains become self-aware, they become conscious. This is a necessary step in the development of advanced simulations, because the brain must realize that it itself has an effect on the world that should be factored into its predictions. Dawkins does not seem entirely satisfied with this explanation of consciousness. Although he does not go into detail about his dissatisfaction, partly it is due to the creation of an infinite loop as the brain is aware that it is aware of itself, and aware that it is aware that it is aware of itself, and so on.3
9. The ancestral population of organisms from which present-day rabbits are descended was probably on average much slower than modern rabbits. However, there was variation in the population; some pre-rabbits were faster than other pre-rabbits. As predator species evolved to make use of pre-rabbits as an easy source of food, the faster pre-rabbits were able to escape slightly more often than their slower relatives. As a result, they were able to produce more offspring. Over many generations, the average speed of the population increased, as traits associated with speed were passed on more often than traits associated with slowness. From time to time, a heritable mutation arose that increased speed even more; these mutations provided a competitive advantage and were also passed on to offspring. This process continued until eventually all individuals in the population were fast runners, and the result is the modern rabbit.4
1. The question of what exactly is the difference between purpose and the appearance of purpose is a door to the large philosophical topic of intentionality.
2. And rehearse behaviors for advantageous situations, should they arise.
3. Also, it seems very easy to program a computer to have a model of itself in the program, but we wouldn’t expect that computer to suddenly start behaving as though it were conscious (in how we commonly think of the word).
4. Imagining rabbits run makes me wonder if they have some kind of neural randomness generator that guides how they dart side to side in their attempts to evade capture.