Why Harsh Environments Breed Darker Personalities
Can harsh environments make societies more self-centered or ruthless?
Posted October 29, 2025 | Reviewed by Lybi Ma
Why are some societies seemingly more self-centered, cunning, or ruthless than others? Your response might be: It's culture. But it’s too easy to blame culture, politics , or even social media . In our new study , published in Evolution and Human Behavior , we suggest that the root of these differences runs deeper: population-level traits are predicted by the ecological conditions in which people grow up.
The Dark Triad traits, namely narcissism , Machiavellianism , and psychopathy , have long fascinated both psychologists and the public: narcissists crave admiration, Machiavellians manipulate and strategize, and psychopaths act impulsively and without empathy. These traits share a common thread of self-interest and social exploitation, but they are distinct and operate via distinct mechanisms.
And over the years, studies have found these traits to influence so many aspects of our lives, including leadership emergence, relationships, and even online behavior. What has been missing, however, is a broader ecological view to explain why entire populations might lean darker or lighter. Based on evolutionary psychology , we explore how ecological environmental factors, including survival rates, sex ratios, and exposure to disease or disasters, can shape collective personality patterns.
Mapping the world’s darker tendencies
Looking at 48 countries and over 11,000 people, we found that a harsh environment leaves a definite imprint on a nation's psychology.
Take narcissism. We found it was higher in countries with more men than women during childhood and adolescence —a scenario that intensifies competition for partners. It also rose in places where the odds of simply reaching age 65 were lower, signaling a world of instability and threat. These kinds of environments seem to reward self-promotion and status-seeking. After all, when life feels short and competition is a daily reality, those are the behaviors that can help an individual stand out.
But here’s the contrast: Places with a heavy burden of infectious disease actually showed lower levels of Machiavellianism and psychopathy. When pathogens are a constant threat, maintaining social harmony and sticking to the rules becomes a life-or-death matter. Deceit or manipulation isn't just wrong —it's a high-risk gamble that could get you excluded from the group. In some contexts, playing nice isn't a moral luxury; it's a core survival strategy.
Disasters, gender, and psychological spillovers
We also found that natural disasters amplify sex differences in dark traits . Men in countries that endured floods, earthquakes, or storms scored higher than women in narcissism, Machiavellianism, and psychopathy. This likely reflects evolutionary pressures toward risk-taking and short-term strategies in unstable environments. However, male-biased sex ratios (more men than women) often reduced these gaps, possibly because women, too, adopt more competitive or self-promotional behaviors when competition for mates intensifies.
Crucially, personality does not stop at national borders. It is entirely possible for spillover effects (that is, neighboring countries’ conditions shaped one another’s psychological profiles), which is what we found in this study as well. For example, nations with high inequality scored higher on narcissism and Machiavellianism than their neighboring nations. It seems that personality can spread through various ecological pathways, including migration and shared regional stressors.
Rethinking the dark side
Our results fundamentally challenge the idea that dark traits are purely individual flaws or cultural quirks. Instead, they look more like adaptive responses to ecological realities.
These findings challenge the idea that dark traits are purely individual or cultural phenomena. It is much more likely that these traits reflect adaptive responses to ecological realities. A harsh, unpredictable world—where your very survival and your chance to compete are uncertain—seems to foster self-enhancement and opportunism. On the other hand, a pathogen-rich world, where you are deeply dependent on your group, rewards conformity and cooperation .
The takeaway is simple: Traits have ecologies. Narcissism, Machiavellianism, and psychopathy are not merely the result of genetics and childhood experiences; these traits are also a result of the survival logic of the environments in which people develop. Knowing this helps us better understand why some societies appear more competitive or self-focused than others. And it reminds us that even our darker impulses are, in part, products of adaptation.
Facebook image: guruXOX/Shutterstock
Jonason, P. K., Gruda, D., & van Vugt, M. (2025). Towards an ecological model of the dark triad traits . Evolution and Human Behavior , 46 (6), 106780.
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Dritjon Jon Gruda, Ph.D. , is an invited Associate Professor of Organizational Behavior at Universidade Católica Portuguesa, Católica Porto Business School and CEGE, and a Lecturer at the National University of Ireland Maynooth.
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