How Evolutionary Psychology Informs Behavior

From a lecture series presented by The Great Courses

Evolutionary psychology helps us to better understand behavioral patterns by linking them to our early ancestors. We’ll trace the journey of evolutionary psychology in academia, beginning with Charles Darwin. We’ll then explore how this type of psychology fell out of fashion, but eventually re-emerged.

Drawing on the wall in a cave, the rock. red ocher paint. Prehistoric man preys on animals deer.
During the long span of human evolution, our prehistoric ancestors faced some recurring challenges, such as the ongoing struggle to find enough food.

Patterns in Personality: Consistencies and Differences

We’re going to start our excursion into the mysteries of human behavior by focusing on personality.

When psychologists use the word “personality,” they’re referring to consistencies in a person’s behavior across various situations and over time—the ways in which a person generally tends to respond. If we followed you around for awhile, we’d see patterns and consistencies in your behaviors and emotions.

And, when we look at people’s emotions and behaviors, we can see two different kinds of consistencies. Some consistent patterns are shared by almost everybody.

For example, most people are consistently uneasy around snakes. Almost everyone is consistently disgusted by rotten food. Just about everybody finds people with clear skin to be more attractive and desirable than people with oozing open sores.

These kinds of consistencies in how we feel and behave are part of human nature. In certain ways, most people are pretty much the same.

This is a transcript from the video series Understanding the Mysteries of Human Behavior. Watch it now, on The Great Courses Plus.

But other patterns of consistency differ across people. Some people generally tend to be outgoing, whereas other people generally prefer quiet, solitary activities.

Some people get emotional more often than other people do. Some people are agreeable and nice, and other people are disagreeable and hard to get along with. Some people are pretty consistently conscientious, and other people are typically irresponsible.

So, to understand the puzzle of personality, we need to examine two types of consistencies: those that are human nature, and shared by almost everybody, and those that are seen in some people, but not in others—what psychologists call “individual differences.”

Learn more about how human nature evolved

Darwin’s Views on Evolution and Behavior

When most people think of evolution, they usually think about how animals’ physical characteristics evolved through natural selection. So they might think about how giraffes got their long necks or why male peacocks ended up having big, colorful tails.

Most people don’t think about the role that evolutionary processes played in the development of behavioral and psychological characteristics.

But we can ask evolutionary questions about behavior, such as why cats hiss rather than making some other noise when threatened, or why many animals react to staring eyes.

Or, getting closer to home, we can ask: Why do people scrunch up their noses when they’re disgusted? Why do people tend to like attractive people more than unattractive people? Why are we are more afraid of snakes than we are of cars? What evolutionary processes led to these consistencies in people’s reactions?

Thinking about evolution is important for understanding certain mysteries of human behavior because, in some cases, the answer to the puzzle has something to do with how human nature evolved.

Charles Darwin. From a photograph by Elliott & Fry.
Charles Darwin recognized that natural selection applied to both physical characteristics and behavior.

Charles Darwin recognized that his theory of natural selection applied not only to the evolution of physical characteristics, but also to behavioral and emotional reactions. But Darwin also knew that his ideas encountered greater acceptance when applied to the evolution of other animals, rather than that of people.

Someone might easily accept an evolutionary explanation for why other animals defend their young, yet have a much harder time agreeing that evolution was involved in making human parents love their children. For that reason, Darwin mostly confined himself to explaining the behaviors of animals other than human beings.

But Darwin saw the potential of evolution to explain aspects of human behavior, as well. In fact, at the end of On the Origin of Species, which was published in 1859, Darwin noted that he thought the field of psychology would someday be based on evolutionary theory.

During the late 1800s, many psychologists began to apply evolutionary thinking in their efforts to understand human behavior. But then an odd thing happened: Psychology abruptly abandoned the idea of evolution, even while biology was rebuilding itself around evolutionary ideas.

Learn more about solving psychological mysteries

Decline and Re-emergence of Evolutionary Psychology

The primary reason behind this shift away from evolution was that mainline scientific psychology became dominated by radical behaviorism, which was based on the idea that all behavior, as well as all emotional responses, are the results of learning. According to behaviorism, people do what they do and feel what they feel because they have been conditioned to respond in certain ways.

Behaviorism dominated scientific psychology for much of the 20th century—at least into the 1960s—which left little room for evolutionary ideas about human nature.

Behaviorism was not wrong about learning and conditioning. Of course, our behavior is partly learned, and our emotions can be conditioned. The faulty assumption in behaviorism was that all behavior is learned.

It wasn’t until the 1980s that evolutionary ideas started creeping back into psychology in noticeable ways. And by the 1990s, a new subspecialty known as evolutionary psychology had emerged, focused specifically on the evolutionary underpinnings of human behavior.

Origins of Evolutionary Psychology

The basic premise of evolutionary psychology is quite simple. During the long span of human evolution, our prehistoric ancestors faced some recurring challenges and problems that had implications for their survival and reproduction.

For example, we had the ongoing challenge of finding enough food. And we faced all kinds of dangers to our physical well-being, from falling out of trees, to eating poisonous materials, to being attacked by animals, to being killed by other people.

We also had to manage our social relationships and deal effectively with other people. We had to manage our sexual lives successfully as well. And if we had offspring, we needed to be able to take care of them.

Young pregnant couple outdoors, husband hugging wife
Humans who survived long enough to reproduce passed on genes that aided in survival.

Some individuals had characteristics that helped them to meet these adaptive challenges more successfully than other individuals. The individuals who had these helpful characteristics—whatever those attributes might have been—were more successful in producing offspring and transmitting their genes to future generations than those who did not tend to respond as adaptively.

As a result, individuals who survived and reproduced successfully passed their genes along at a higher rate, including the genes that were associated with those behaviors that helped them meet the challenges of daily life more successfully. Individuals that did not survive or reproduce as successfully did not pass along their genes at the same rate. Genes that were associated with less adaptive patterns of behavior therefore decreased in the species over time.

That process is how psychological characteristics evolved—individuals with characteristics that promoted survival and reproduction passed along their genes at a higher rate. Today’s humans, then, are the descendants of those individuals throughout evolutionary history who were most successful at surviving and reproducing.

If all members of a species share a particular characteristic, one explanation is that the characteristic was adaptive for generation after generation of our ancestors.

From the lecture series Understanding the Mysteries of Human Behavior, taught by Professor Mark Leary

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Images Courtesy of:
Elliott & Fry [Public domain], via Wikimedia Commons