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Evolution Explains Puzzling Aspects of the Human Mind

Evolution helps explain anxiety, the hedonic treadmill, and other puzzles.

Key points

  • Evolution explains puzzling aspects of the human condition, including anxiety and the hedonic treadmill.
  • Evolutionary theory sheds light on a wide variety of topics, ranging from personality to immune function to psychopathy (and beyond).
  • Without evolutionary theory, our understanding of the human mind would be considerably diminished.

This essay is the fourth in a series on evolutionary approaches to the mind. They don’t need to be read in order.

  1. Part 1: Key Misconceptions
  2. Part 2: Levels of Analysis
  3. Part 3: Predicting New Findings
  4. Part 4 (this post): Explaining Known-but-Puzzling Findings

Evolutionary approaches have led to many new discoveries in the social and cognitive sciences. But the process also works in the other direction: evolution explains aspects of the human condition that we already know about, but that are puzzling without the light of evolution. Consider anxiety.


Anxiety is useful because it alerts us to danger, but our anxiety seems hyperactive and too easily triggered—to the point where it often hurts rather than helps us. Why are we so anxiety-prone?

The picture comes into relief when you consider how our brains evolved. When it comes to detecting danger, we can make one of two mistakes: we can fail to detect a real threat or we can “detect” a threat that isn’t really there. Of these two possible errors, failing to detect a real threat is much more costly. So our anxiety mechanisms have evolved to be “adaptively biased” in the direction of the safer error—toward false alarms. Our anxiety is hyperactive for the same reason that our smoke detectors are overresponsive: a systematic bias toward false alarms minimizes the likelihood of the more catastrophic error. It’s not a bug; it’s a feature. If you want to stay alive, analyses show that this setup is better and safer than less “paranoid” designs.

If it weren’t for the light cast by evolutionary theory, the hyperactivity of our anxiety mechanisms would seem inscrutable. Why would any process, we might wonder—whether natural selection or a deity or anything else—forge brains bogged down by so much excess anxiety? Evolutionary thinking resolves the mystery and offers us the gift of self-knowledge along the way.

The Hedonic Treadmill

What happens after you achieve a goal? The answer is both familiar and unfortunate: after a short-lived pride, our happiness dissipates and we revert to our baseline mood. Our sense of contentment and accomplishment fade. Wanting and craving naggingly reassert themselves.

This is the curse of the hedonic treadmill. Many of us resent having to watch our happiness dissolve so soon after we’ve accomplished something important—and the apparent irrationality of it makes it much worse. Perplexed and frustrated, many of us wonder: why am I like this?

Imagine our hominin ancestors. After achieving a goal, some rested on their laurels for a long time, whereas others returned to their emotional baseline and began craving their next accomplishment. In a population composed of both types, who do you think would have been most successful: those who were easily satisfied once they achieved an initial goal, or those whose hankering to achieve their next goal constantly reasserted itself?

The hedonic treadmill is a cruel Sisyphean affliction, yes, but our brains evolved this way for a reason.

Self-Understanding and Pain Relief

An evolutionary perspective helps us make sense of the hedonic treadmill’s apparent irrationality. But I think the understanding does more than shed light—it also relieves some of the pain. Seeing the adaptive logic that undergirds the surface-level irrationality makes our suffering seem a little less pointless. It makes the hedonic treadmill feel a little less cruelly absurd.

Just as it did with the puzzle of our excessive anxiety, an evolutionary perspective offers genuine self-insight here. Grasping something so profound about yourself can feel almost enchanting. It’s a unique kind of comprehension: understanding why you are the way you are. Little compares with it.

Other Puzzles in the Social Sciences

Evolution helps solve other puzzles in the social and cognitive sciences, too. For example, why do we learn some things easily and with no formal instruction, such as how to speak and understand spoken language, but others only with difficulty and after much formal instruction, such as how to read and write? Perhaps it is because we have evolved adaptations specifically for speaking and understanding language, whereas reading and writing are more recent innovations, and are likely byproducts (side effects) of abilities that evolved for spoken language. The same reasoning may also help us understand why computers outperform us on some tasks, but fall short on others. Artificial intelligence systems beat us handily at calculus, chess, and (more recently) Go, but children often trounce them at tasks like recognizing faces, understanding language, and manipulating objects—perhaps partly because we have evolved dedicated neurocognitive machinery for face perception, language processing, and object manipulation, but not for chess, Go, or calculus.

Evolution also explains why in most species—including humans—females have stronger immune systems than males. Natural selection typically fashions bodies that are good for survival, but sexual selection often pulls in the opposite direction, leading to bodily designs that benefit reproduction at the cost of survival. Examples include the peacock’s burdensome tail, the redback spider’s voluntary cannibalistic self-sacrifice, and the immunosuppressive effects of testosterone—all of which are helpful for reproduction but bad for survival. Because in most species, sexual selection acts more strongly on males than it does on females, it tends to pull the male bodily design further away from the engineering optimum for survival, burdening it with ornaments and weapons that increase the likelihood of successful reproduction at the cost of reduced survival. This is why females have superior immune systems compared to males in many species, and why the female bodily design is often closer to the engineering optimum for survival.

As it turns out, a great many findings in the social and cognitive sciences don’t really make sense except in the light of evolution. For example, evolutionary thinking helps explain why our dreams include specific sensory modalities and why our bodies are vulnerable to disease. Without evolutionary theory, it would be difficult to make sense of the Coolidge Effect in male animals. Specific mate preferences, such as for facial symmetry or deep voices, would seem arbitrary and inexplicable. Evolution yields insights about topics in psychology and behavior as wide-ranging as maternal-fetal conflict in the womb, conflict between children and parents over the children’s mating decisions, why personality differences are heritable, why psychopathy hasn’t been filtered out of human populations, why we crave foods that are bad for us, why suppressing fever can be harmful, why ostracizing someone is one of the most agonizing things you can do to them, why Taiwanese “minor marriages” are plagued with sexual and romantic difficulties, why male aggression peaks during the teen and young adult years, why humans have an “auditory looming bias” that applies to harmonic tones but not to broadband noise, why indirect speech has the characteristics that it does, why mental disorders have the features they do, why coalitional psychology works the way it does, and why non-infectious objects sometimes trigger disgust.

Crucially, the claim that evolution helps explain these phenomena does not imply that they are all adaptations. Many of the explanations linked above are distinctly non-adaptive in nature.

Equally crucially, please don’t fall into the common trap of thinking that evolutionary reasoning can only be used to explain known facts, but not predict new ones. There are hundreds of examples of new predictions (and discoveries) generated by evolutionary approaches to the mind. A few dozen are described here.

What Does Evolutionary Theory Offer the Social and Cognitive Sciences?

Evolutionary thinking sometimes helps solve longstanding mysteries about human psychology and behavior. In other cases, it sheds unexpected light on subjects we thought were already fully illuminated. In still others, it generates precise new predictions about human psychology and suggests new questions we hadn’t previously thought to ask.

This combination of proposing new questions, predicting previously unknown findings, and explaining known-but-puzzling features of the human condition is the sign of an immensely fruitful theoretical framework. Without evolutionary theory, our understanding of the human mind—in all of its wondrous complexity and charming quirks—would be considerably diminished.

More from Laith Al-Shawaf Ph.D.
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