Over the past two decades, many social psychologists have begun looking to the theory of evolution to help explain social behavior.
The theory of evolution, proposed by the British biologist Charles Darwin in the 1800s, focuses on how change occurs in nature. Over thousands of years, a type of plant or animal may evolve into a somewhat different kind of creature. Human beings and the great apes evolved from a common ancestor.
Human beings may be different from all other animals, but we are animals nonetheless. As such, we have many of the same wants, needs, and problems that most other animals have. We need food and water on a regular basis, preferably a couple of times every day. We need sleep. We need shelter and warmth. We need air. We suffer illnesses and injuries and must find ways to recover from them. Our interactions with others are sometimes characterized by sexual desire, competition, aggressive impulses, family ties, or friendly companionship. Sometimes we say that certain people are “acting like animals,” but this is not surprising, because we are all animals. Th at phrase merely expresses the point that people can sometimes rise above their animal nature, but the animal parts are there inside all of us.
An important feature of most living things, including animals and hence humans, is the drive to prolong life. Th ere are two ways to do this. Obviously, one way is to go on living. (Wouldn’t you like to live forever? Death has always been a disturbing threat, and beliefs that death is not the end but merely a transition into a different kind of life, whether as a ghost, a spirit in heaven, or a reincarnated person, have been found all over the earth since prehistoric times.) Th e other is reproduction: Life makes new life. Indeed, you might say that nature was unable to create an immortal being and therefore settled on reproduction as the only viable strategy to enable any form of life to continue into the future.
Change is another common trait of living things. Each living thing changes as it grows older, but more important forms of change occur from one generation to the next: Children are different from their parents. Nature cannot plan ahead and design a certain kind of change. Instead, nature produces changes that are essentially random. Th at is, the complicated processes that mix the genes of two parents to produce a unique set of genes in the baby sometimes produce novel outcomes in the form of new traits. However, there are powerful forces that react to these random changes. As a result, some random changes will disappear, whereas others will endure. Th e process of natural selection decides which traits will disappear and which will continue.
For example, imagine that one baby was born with no ears, another with one leg longer than the other, and the third with eyes that could see farther than the average eye. Having no ears or having legs of unequal length would probably be disadvantages, and natural selection would not preserve these traits for future generations. (That’s a polite way of saying that those babies would probably die before being able to pass on their genes by having off spring.) A significant improvement in vision might however be selected to remain, because the baby who grew up seeing better than other people would be able to find more food and spot danger from a safer distance. The genes for better vision would therefore remain in the gene pool (assuming that this baby would grow up and have babies), and so in future generations more and more people would enjoy this improvement.
Natural selection operates on the basis of two criteria: survival and reproduction. (Remember, these are the two ways of prolonging life.) A trait that improves survival or reproduction will tend to endure for many generations and become more common. A trait that reduces one’s chances for survival or reproduction will probably not become common. These are crucial themes, because the biological success of any trait is measured in those terms. A novel trait that makes someone happier, or gives the person higher self-esteem, or fosters a weird sense of humor, will not necessarily be passed on to future generations, unless those changes can translate into better survival or better reproduction.
