Brief Summary
Richard Dawkins discusses the concept of natural selection and its role in shaping the diversity and complexity of life. He explains how random genetic mutations provide the raw material for variation, while non-random survival of genes leads to evolution towards better survival and reproduction. He also touches on the imperfections in nature, using examples like the flatfish eye and the recurrent laryngeal nerve to illustrate how evolution works with existing structures, leading to compromises rather than perfect designs.
- Natural selection drives the evolution of life, favoring traits that enhance survival and reproduction.
- Random genetic mutations provide the raw material for variation, while non-random survival of genes leads to evolution.
- Imperfections in nature, such as the flatfish eye and the recurrent laryngeal nerve, demonstrate how evolution works with existing structures, leading to compromises rather than perfect designs.
Introduction
In 2012, Richard Dawkins participated in an interview for the "Great Minds" program produced by the Educational Broadcasting System in South Korea, where he discussed science, rational inquiry, and the evolutionary perspective on life. He hopes the conversation will be thought-provoking.
Natural Selection and Random Mutation
All the wonders of life, including its elegance and the illusion of design, stem from natural selection. Random genetic mutations, which are random changes in genes, provide the raw material for variation. While most of these mutations are harmful, a minority of them lead to improved survival and reproduction. Darwin used the example of domestication to explain this concept, noting how farmers and animal breeders have long influenced changes in breeds through artificial selection. This process, which has been known for thousands of years, demonstrates the power of selection in shaping the characteristics of organisms.
Small Mutations and the Analogy of the Microscope
Geneticists study mutations of large effect, but these are not the important mutations in evolution because they are highly likely to be harmful. Small mutations are the ones that are important in evolution. Ronald Fischer, a pioneer of Darwinism, used the analogy of a microscope to explain this concept. He pointed out that a microscope needs to be in focus, and only a small change in the height of the tube is needed to bring it into focus. A large change is bound to be worse, either going miles out of focus or crashing through the slide.
Imperfection in Nature
Evolution does not lead to perfection because natural selection has to work with what is already there. Unlike an engineer who can start from scratch, evolution has to modify existing structures step by step. The lung, for example, evolved from the swim bladder in fish. There are some beautiful examples of imperfection in nature, such as the flatfish eye and the recurrent laryngeal nerve. The flatfish eye migrates around to the other side of the head, which is an obvious imperfection. The recurrent laryngeal nerve takes a ridiculous detour down into the chest and back up again to the larynx.
Examples of Imperfection: Flatfish Eye and Laryngeal Nerve
Flatfish have both eyes on the same side of the head, which is an obvious imperfection. The laryngeal nerve in mammals, reptiles, and birds goes from the brain to the larynx, but one branch goes down into the chest, loops around a main artery, and then goes back up to the larynx. This is a ridiculous detour. The reason for this lies in history: in fish ancestors, the equivalent of that nerve went behind the artery, which was the most direct route at the time. As necks evolved, the detour of the nerve going around the artery became a slight detour, and the cost of jumping the nerve over the artery was too great.
The Retina of the Eye
The retina of our eye is back to front, with the photo cells pointing backwards. The nerves that connect the photo cells to the brain have to find their way around the retina, going across the surface and then diving through a hole called the blind spot into the optic nerve. This is a ridiculous piece of bad design. The great German physiologist Helmholtz said that if he had been handed the eye designed by an engineer, he would have sent it back.
Compromises and Economic Costs
Imperfection is a necessary part of the way evolution works because of costs. Darwinian design is a compromise between relatively incompatible pressures. Natural selection can be thought of as a whole lot of pressures pushing in different directions. For example, the need for a male bird to be brightly colored to attract females is pushing him in the evolutionary direction of being brightly colored, but predators are also attracted by bright colors, which is pushing in the opposite direction. There is also compromise between different selection pressures like sex and predation, as well as economic costs.
