What Is Evolutionary Psychology, Anyway?

When a feline gets threatened, it engages in a suite of behaviors that seem to have the purpose of facilitating its own survival. A cat will growl angrily. It will arch its back. And even the fur on the back will stand up, giving the overall impression that it is fierce and is larger than it actually is.

Darwin noticed all these phenomena and published about this in his 1872 classic, The Expression of Emotion in Man and Animals.¹ Darwin explained these behavioral reactions in terms of natural selection, with the idea that ancestral cats that manifested these behaviors under threatening conditions were more likely than were others to actually survive and, ultimately, reproduce.

While the modern field of evolutionary psychology includes a broad array of nuanced evolutionary concepts that extend beyond natural selection, the idea of some behavioral strategy as having the evolved function of increasing the likelihood of survival and reproduction of individuals sits near the core of evolutionary psychology writ large. To a large extent, evolutionary psychology is an approach to understanding human behavior in a way that is parallel to how Darwin understood threat-responses in felines. Humans, like all animals, have many evolved behavioral, emotional, and social strategies that seem to have the evolved function of increasing the probability of survival and reproduction.

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5 Basic Principles of Evolutionary Psychology

The evolutionary approach to psychology has been famously misunderstood and misrepresented by scholars from outside the field.²Various misconceptions, such as the idea that the field is about creating a super-species or that the field is only about behavioral differences between men and women, are, in fact, commonly held. This article is largely designed to provide a brief, foundational summary of some of the core ideas of the field with an eye toward helping people understand what this approach to behavior truly is about. (Many of the ideas here are, in fact, distilled versions of concepts presented in my book, Evolutionary Psychology 101,³ which is designed to provide a basic introduction to the field.)

Based on my experience of working in the field of evolutionary psychology for the better part of the past three decades, here are five foundational ideas that, in combination, provide the guts of an evolutionary approach to behavior.

1. Behavior ultimately results from natural selection.

As is the case with threat responses in cats, described above, many human behaviors can be thought of as having evolved via natural selection to help facilitate survival and/or reproduction. Just as cats are biologically prepared to show adaptive responses to threats in their environments to help facilitate their own survival and reproductive success, humans show a plethora of behavioral responses that serve the function of facilitating survival and reproduction and that likely have their roots in natural-selection processes.

For instance, as with cats, humans have a broad suite of physiological and behavioral responses that emerge in light of threats (this is often called the fight or flight response and it mobilizes our minds and bodies for dealing with threats). Such a natural-selection-based analysis can help us understand so many features of human behavior—from why we prefer the foods that we do to why infidelity is so stressful in relationships to why people often turn to religion... and on and on. The idea of natural selection as having shaped so much of human behavior is, in a sense, the core idea of evolutionary psychology.

2. Reproductive success as Darwin's bottom line.

As is true with all organisms, our ancestors successfully became ancestors because they had features that facilitated their own reproductive success. Evolutionary psychology is not at all about "what is best for the species." Evolution, in fact, doesn't work that way at all. Along with other evolutionary processes, natural selection favors attributes that ultimately facilitate successful reproduction at the individual level.

From an evolutionary perspective, survival is a tool toward successful reproduction. So adaptations that facilitate survival are critical—but they, in effect, take a back seat to adaptations that ultimately facilitate reproduction. From an evolutionary perspective, reproductive success is ultimately Darwin's bottom line.⁴

3. Ancestral conditions of an organism importantly relate to modern behavior.

From an evolutionary perspective, organisms evolve under certain specialized ecological conditions over extended periods of time. If you want to understand why an organism does what it does, sometimes you need to look back at the environmental conditions that surrounded the evolution of the organism.

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For the lion's share of human evolutionary history, our ancestors lived in small nomadic bands in the African savanna, where drought and famine were common. Under such conditions, extensive daily physical activity was essentially required. Further, dealing with other people in small-scale, tight-knit nomadic groups was part of everyday life. These features of our ancestral conditions ultimately shaped how we are today. To understand human evolved psychology, it is often helpful to look toward our past.

4. Behavioral flexibility is a core part of our evolved psychology.

Like all animals, humans show a remarkable degree of behavioral flexibility. We evolved to take the environment into account. This is why people stay indoors when it is cold but go outside when it is warm and sunny. Our behavior is not fixed—we evolved to adjust our behaviors based on ecological conditions.

And such behavioral flexibility is clearly adaptive. This concept is well-demonstrated in the idea of life-history strategy,⁵ which is the idea that people adjust their adult social behaviors based on the kinds of environments they experienced earlier in life. People who grow up in highly unstable, resource-depleted environments tend to engage in behaviors consistent with a "fast" life history strategy, implicitly assuming that life may be short. On the other hand, people who grow up in highly stable environments are more likely to take a "slow" approach to life, acting as they are implicitly expecting a long lifespan.

A core principle of evolutionary psychology, then, is this: Evolutionary psychology sees evolved behavioral flexibility as a core feature of our minds and behaviors.

5. Evolutionary principles bear on all human behavior.

Generally speaking, evolutionary psychologists do not see this approach to behavior as limited to a subset of phenomena (such as the emotion system or the nature of human mating). In fact, as is explicated in my and Nicole Wedberg's recent book Positive Evolutionary Psychology,⁶ our evolutionary history shapes pretty much any and all facets of the human psychological experience. This approach to psychology has helped us better understand such variegated topics as human warfare, love, education, politics, social interactions, mental health, physical health, and more. The evolutionary approach to psychology helps to shed light on the entirety of the human experience.

Bottom Line

Evolutionary psychology is famously often misunderstood and misrepresented.² I aim to shed light on the basics of this field. At its core, evolutionary psychology is an approach to psychology that sees our behavior as part of the natural world. Understanding the core evolutionary principles delineated here can help anyone better understand the world and our place in it. If you want to understand what it means to be human, you dismiss the evolutionary perspective to your own detriment.

Note: Special thanks to Cali Bird for the editorial suggestions.