How The Mind Works

The Voyager 2 space mission was to fly to the outer edges of our solar system and send back data. The Voyager 2 included recordings of music, human sounds, an EEG recording, and other representations of human civilization. If an extraterrestrial were to find it, we wanted it to show them who we were. Some people have thought the idea of intelligent extraterrestrials to be crazy, and others have thought of it as a certainty. Pinker argues that it is unlikely that human-like intelligence has developed elsewhere and that people who argue that it most certainly has evolved elsewhere do not understand how natural selection works. There is an assumption that intelligence is a goal of natural selection, but natural selection does not have goals. The only “goal” that could be ascribed to natural selection is passing on genes. The genes want to make it to the next generation. They do that by being beneficial to most of the population.

Arguably, intelligence would be beneficial to a lot of organisms, but just like any other complex, evolved organ, the human brain and the intelligence it allows are costly. The brain makes up 2% of the weight of the human body but uses 20% of its energy. The energy required to develop and maintain the brain can’t go to other developments. Humans are not particularly fast or strong compared to many other creatures. We are not particularly large or flexible. Our brains allow complex feats, but they also slow down some simpler processes, like reaction time. These trade-offs must be made for every organism and are part of the intricate process of natural selection. One side of the trade-off will win, and intelligence is just one option among many to increase survival.

Natural selection is the only theory that has stood the test of time in explaining how living organisms came to be. Previous theories, such as Lamark’s use and disuse and inheritance of acquired characteristics theories, fail to explain the full picture of evolution, and they attribute agency to organs and individual cells, a view that does not fit with modern understanding of biology. Others have proposed macromutations, or large changes, in the genome that bring about complex organs like the eye, and yet mutations of these size are so unlikely the theory is not supported. Even more unlikely is the idea that these mutations would always be beneficial. If macromutations occurred, we should expect to see examples of catastrophically wrong mutations just as we see beneficial ones. It is much more likely that very small mutations that slightly improve an organism’s chance of surviving are passed down. These mutations would be less likely to upset the entire balance of the organism and more likely to occur over hundreds and thousands of years. Additionally, those small mutations can be seen when we examine evolutionary chains, supporting the natural selection explanation.

There is very deep-rooted antagonism towards natural selection. Many scholars have been avidly against it and thrown up arguments that demonstrate limited understanding of natural selection. Most arguments involve a straw man, or a made-up problem that is easily torn down. Once torn down, the entire theory can be discarded as useless. One common straw man is “what use is half a wing,” which is the idea that the product, a bird’s wing, is very useful, but the intermediate products could not have been useful and would not have been passed on as beneficial for survival. This argument typically goes with the argument that natural selection doesn’t explain why some functional organs (wings are also a classic example) aren’t used for their original purpose. Following the evolution of the wing, it’s clear that intermediate versions were useful, just not for flying. Wings helped with heat insulation, and larger wings provided better insulation. As wings grew, they eventually reached a size at which they could be used for flight, which could help with finding prey, evading predators, and finding the best nesting locations. Once used for flight, the wings could continue to grow and be optimized for flight.

Knowing that natural selection drives evolution, it’s time to turn to the brain’s evolution. Pinker argues that brains evolved because information is valuable. Knowing where a predator is or the best route to a source of food improves survival. Brains are information-processing units, and their evolution, like that of other organs discussed in the book, is driven by natural selection to fit the environment of the creature in question. For humans, our brains evolved for us to survive in our unique environment with our specific bodies and skills, and the brain of a zebra or a cat will evolve for their environments. Birds have evolved brains that handle the unique ways they each navigate while flying, and many of these abilities are impressive. There isn’t a linear path from animals with smaller brains to animals with larger or later-evolved brains. Brains develop their unique information-processing abilities based on the environments and what is required to survive, and even animals with small, simple brains can do some amazing things.

A good question is why primates were the ones to evolve into humans with particularly advanced brains instead of another creature. Pinker argues that four primate traits may have predisposed them to more rapidly evolve their information-processing abilities. First, primates have well-developed visual systems because they were useful for living in trees and eating bugs and fruit, but other animals tend to rely on smell. A primate’s visual system allows depth perception (having two eyes), and that means that primates live in a 3D world, whereas other animals live in a 2D world. The 3D world offers considerations of how objects move and how to manipulate them and allows for better planning because of the ability to see down a path. Second, primates live in groups. These groups allow sharing of knowledge, which increases intelligence and creates pressure to compete among one’s own species. Competition means you need to be smarter than the other to win food, mates, shelter, or any other potentially scarce resource.

Third, primates have hands that can manipulate objects precisely. That precision allowed greater tool development and the use of farther-away resources because they could be carried to where they were needed. Intelligence is useful to design more and better tools, something humans have done for millennia. Finally, primates are hunters, and hunting increases meat consumption, which supplies proteins, fats, and energy needed by larger brains. Successful hunting can produce larger brains, which can be passed down to future generations. These four traits and the environmental pressures that brought them about are unique to primates and humans. Other intelligent creatures had some of these pressures, but not all of them in the combination that resulted in human levels of intelligence, and it is unlikely other species will face similar pressures.