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Evolutionary Psychology

5 Dark Facts About Life, Informed by Evolutionary Psychology

Life is not always peaches and cream. Evolutionary psychology tells us why.

Key points

  • People engage in various acts that hurt others; once those phenomena are fully understood, they can be more properly addressed.
  • Evolutionary psychology sheds light on the dark side of human experience, including phenomena such as homicide, infidelity, and early mortality.
  • Those outside evolutionary psychology may subscribe to the "naturalistic fallacy," assuming "natural" behaviors are also justified.
Source: activedia/Pixabay

If you're old enough to read this, you know that life is not always peaches and cream. While life can be both beautiful and even awe-inducing at times, human life often comes with a dark side as well.

The evolutionary perspective in the behavioral sciences, which sees human behavior as resulting from such evolutionary processes as natural and sexual selection (see my book Evolutionary Psychology 101 for a quick guide to the field), sheds light on the entirety of the human experience, from the brightest aspects of our lives, such as true love, to the darkest sides of the human experience, such as homicide—and everything in between.

Sometimes people criticize the field of evolutionary psychology for not addressing phenomena that are relevant to important social issues of the day. Partly to address this misconception, here, I provide five dark facts that we know about the human experience as a result of insights from the field of evolutionary psychology.

5 Dark Facts Associated With Being Human

1. Homicide is strongly tied to infidelity.

In their groundbreaking work on homicide from an evolutionary perspective, Daly and Wilson (1988) report a broad range of relatively disturbing facts about the nature of homicide in modern humans. Based on large samples of crime data obtained from Toronto and Detroit, they came to various dark conclusions, one of which is this: About 1/3 of all homicides result from male emotional and behavioral reactions to infidelity.

From an evolutionary perspective, they argue that this finding stems from the fact that sexual infidelity is a major adaptive hurdle for males, as ancestral males who were victims of infidelity may well have ended up unwittingly raising young sired by other males. Given how evolution operates, by selecting features that increase the reproductive success of an individual organism, strong negative reactions on the parts of men in the face of infidelity can be better understood.

2. The Cinderella Effect and filicide: Step-parenting is not always pretty.

These same researchers, Daly and Wilson, also report data on the extremely dark phenomenon of filicide: the killing of one's own young. Based on extensive research on this topic, it turns out that step-parents are more likely to engage in filicide than biological parents. And this effect is literally off the charts for the kinds of effects we tend to see in the behavioral sciences (see Daly & Wilson, 1988). Daly and Wilson refer to this phenomenon as "the Cinderella Effect," helping us to understand why the evil step-parent trope is so prevalent. It taps our evolved psychology.

3. Cheating of all kinds is rampant in the human experience.

It would be great if people could trust others to do the right thing and to be generally above board and honest. But you probably realize that this is not always the case. In fact, people cheating in social contexts (in terms of not doing their fair share for the group, engaging in infidelity, etc.) has been such a recurrent problem for humans that we seem to have evolved strong cheater-detector mechanisms (see Cosmides & Tooby, 1992) as a way to deal with cheaters in our midst. Our logical abilities literally turn up a notch when we are thinking about issues connected to cheating. Think about that.

4. In-group/out-group thinking is a human universal, often leading to intergroup conflict.

One of the easiest social psychological phenomena to replicate is found in work on in-group/out-group thinking (see Billig & Tajfel, 1973), which is basically a biased form of social cognition in which people seem to over-favor members of their own group (defined in a number of ways) relative to those whom they seem as "others." This phenomenon is a strong tendency and seems to be rooted in our ancestral environments in which people lived in small nomadic clans that often were sometimes in conflict with other clans for access to resources. By all kinds of research-related accounts, this phenomenon, which leads to all kinds of social problems at all kinds of levels (e.g., between nations, between people of varying political orientations, etc.), is deeply rooted in our evolved psychology (see Wilson, 2019).

5. Young adult males are way more likely to die prematurely relative to females.

Classic work on the male-to-female mortality ratio (Kruger & Nesse, 2006) found that, across time periods and cultures, young males (roughly between the ages of 15-25) are much more likely to die prematurely relative to their female counterparts. In some of the data, males were up to four times more likely to find early death relative to females during this stage of life.

These researchers appeal to an evolutionary perspective in explaining this phenomenon, noting that these years are prime mate-selection years in the human life cycle and that males are, relative to females, much more likely to take physical risks and engage in physical aggression with members of their own sex, often connected with mating efforts. Unfortunately, sometimes, leading to premature death.

Let's Avoid the Naturalistic Fallacy

One important note about these findings is this: I don't like any of them! I am not a fan of homicide nor filicide nor cheating nor prejudice nor early male mortality. This, I can promise you.

I make this point for a very specific reason. It is common for people outside of evolutionary psychology to make what we call the "naturalistic fallacy," which exists when someone hears about a phenomenon being framed as "natural" and misinterprets things so that the phenomenon is being seen as somehow justified or is being framed as how things should be.

This fallacious thinking is a major hurdle for scholars in the evolutionary behavioral sciences who are, like scholars in any scientific field (ideally), looking to better understand phenomena—as opposed to trying to, somehow, endorse or prescribe those same phenomena.

There is a big difference between saying that infidelity is a significant cause of homicide relative to saying that people who suspect infidelity ought to engage in homicide. The importance of this particular point really cannot be overstated. Without an understanding of this distinction, it becomes nearly impossible for someone to fully understand and appreciate the evolutionary perspective on the human condition.

Bottom Line

While life is often beautiful (see my and Nicole Wedberg's book, Positive Evolutionary Psychology, for a treatise on this part of life), it can also, at times, be quite hard. Murder, cheating, ethnic discrimination—these are all part of the broader human experience, whether we like it or not.

The evolutionary perspective can help us better understand these particular dark features of the human experience. And only once we understand a phenomenon fully are we equipped to figure out how to address it.

Want to better understand some of the largest social problems that exist in humans across the globe? I'd say you probably should brush up on your understanding of evolutionary psychology.


Billig, M., & Tajfel, H. (1973). Social categorization and similarity in intergroup behaviour. European Journal of Social Psychology, 3, 27–52.

Cosmides, L. & Tooby, J. (1992). Cognitive adaptations for social exchange. In J. Barkow, L. Cosmides, & J. Tooby (Eds.), The adapted mind: Evolutionary psychology and the generation of culture. New York: Oxford University Press.

Geher, G. (2014). Evolutionary Psychology 101. New York: Springer.

Geher, G. & Wedberg, N. (2020). Positive Evolutionary Psychology: Darwin’s Guide to Living a Richer Life. New York: Oxford University Press.

Kruger DJ, Nesse RM: An evolutionary life history understanding of sex differences in human mortality rates. Human Nature,74 (1): 74-97, 2006.

Wilson, D. S. (2019). This View of Life: Completing the Darwinian Revolution. Pantheon: New York.

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