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Why Are Poland and Peru Similar?

Understanding cultural similarities through ecology.

Key points

  • Ecology can explain some of the similarities and differences we see between cultures.
  • A new dataset allows users to explore relationships between ecological and cultural variables.
  • Poland and Peru have similar ecological variables such as life expectancies and low levels of infectious disease threat.

Coauthored by Alexandra S. Wormley and Michael E.W. Varnum

You probably wouldn't be too surprised to learn that Poland and Ukraine are similar in terms of values, but what about Poland and Peru? It turns out these societies also cluster quite closely. Social scientists have long studied why cultures vary in terms of values, motivations, and attitudes. Often this research has revealed familiar clustering by history, religion, or geographic proximity. Yet, despite the physical gap between Lima and Warsaw, we see that these two countries are similar in how much they emphasize values like harmony and independence (Fig. 1; Schwartz, 2007).

Source: Wormley et al., 2022 (Scientific Data)
The dendrogram represents the cultural values of 43 countries. Shorter heights in between branches indicate greater similarity.
Source: Wormley et al., 2022 (Scientific Data)

Why might we find such unexpected similarities? The answer may have to do with ecology, the basic features of the physical (i.e., rainfall or temperature), and social environment (i.e., GDP per capita, population density) that have important consequences for behavior among humans as well as other animal species. It turns out that ecology may also help us to understand patterns of cultural variation around the world. Indeed, a number of studies have shown that cultural differences in things like the strength of social norms (Gelfand et al., 2011), individualism (Fincher et al., 2008), and even fertility (Rotella et al., 2021) appear to be linked to variations in key features of the ecology.

In one view, ecology may lead to cultural variation through evoked responses-- adaptive behavioral and psychological responses to recurrent environmental threats and affordances (Sng et al., 2018; Tooby & Cosmides, 1992). Like other animals, humans respond to such environmental cues in ways that may lead to regional variations in how we act and think (Barsbai et al., 2021; Sng et al., 2018). Thus, if different groups experience systematically different ecological conditions, we might expect systemic psychological variation across these groups.

Another way in which ecology may be linked to cultural variation is that societies may develop institutions and rules designed to respond to these environmental pressures (Nichols, 2022). For example, a culture might promote strict social norms with harsh punishments for violators to keep individuals in line when there are external threats, like natural disasters, to contend with (Gelfand et al., 2011). As another example, greater levels of pathogen threat are related to more collectivistic and ethnocentric institutions, alongside more social conservatism (Brown et al., 2016).

In our latest work, we created a comprehensive dataset of ecological indicators and seventy-two cultural variables for 220 societies to evaluate just how far the relationship between ecology and culture goes while enabling other scholars to further their own work on the topic. The dataset encompasses a wide range of cultural variables of interest to social scientists, including prejudice, personality, motivations, and institutional variables such as the rule of law, corruption, and democratic practices. Our dataset also contains information not only on current levels of ecological variables but also on how these variables change over time.

By bringing this information together in a systematic way, our new dataset enables scientists to answer a number of important questions. For example, how strong is the overall linkage between ecological conditions and cultural variation (Wormley et al., 2022)? Are some metrics of ecology, such as averages or ranges, better predictors than others, such as current levels or predictability? Do societies cluster differently on different types of cultural variables like personality? How might ecological differences between societies' similarities relate to phenomena like acculturation? These are just a handful of questions that we hope this new database will enable researchers to answer, and indeed we are working on some of these questions ourselves. In the spirit of open science, we have made this dataset freely available to anyone (including you!), along with a detailed description of the dataset in our publication in Scientific Data.

Wormley et al., 2022 (Scientific Data)
Dendrogram representing current levels of ecology. Shorter heights in between branches indicate greater similarity.
Source: Wormley et al., 2022 (Scientific Data)

So why are Poland and Peru so surprisingly similar in values? Well, it turns out that they also bear some striking similarities in terms of the ecological variables we have studied (Fig. 2). Both have similar life expectancies (73.5 and 75.2 years, respectively) and similarly low levels of infectious disease threat, for example. This suggests another way this dataset may be useful for researchers–namely. It might help us to anticipate cultural similarities that we might not otherwise suspect. The Amazon rainforest and the Amazon’s headquarters (in Seattle, WA) are rainy places. Might we see similar cultural and institutional features that arise in response to that rain? The Eco-Cultural Dataset is one tool that we hope will allow researchers to tackle these questions and many others in the years to come.


Barsbai, T., Lukas, D., & Pondorfer, A. (2021). Local convergence of behavior across species. Science, 371(6526), 292–295.

Brown, G. D. A., Fincher, C. L., & Walasek, L. (2016). Personality, parasites, political attitudes, and cooperation: A model of how infection prevalence influences openness and social group formation. Topics in Cognitive Science, 8(1), 98–117.

Fincher, C. L., Thornhill, R., Murray, D. R., & Schaller, M. (2008). Pathogen prevalence predicts human cross-cultural variability in individualism/collectivism. Proceedings of the Royal Society B: Biological Sciences, 275(1640), 1279–1285.

Gelfand, M. J., Raver, J. L., Nishii, L., Leslie, L. M., Lun, J., Lim, B. C., Duan, L., Almaliach, A., Ang, S., Arnadottir, J., Aycan, Z., Boehnke, K., Boski, P., Cabecinhas, R., Chan, D., Chhokar, J., D’Amato, A., Ferrer, M., Fischlmayr, I. C., … Yamaguchi, S. (2011). Differences Between Tight and Loose Cultures: A 33-Nation Study. Science, 332(6033), 1100–1104.

Nichols, R. (2022). The Institution as an Explanatory Mechanism in Cultural Evolution: A Review of Three Theories. Journal of Cognition and Culture, 22(5), 499–513.

Rotella, A., Varnum, M. E. W., Sng, O., & Grossmann, I. (2021). Increasing population densities predict decreasing fertility rates over time: A 174-nation investigation. American Psychologist, 76(6), 933–946.

Schwartz, S. H. (2007). Value Orientations: Measurement, Antecedents and Consequences Across Nations. In R. Jowell, C. Roberts, R. Fitzgerald, & G. Eva, Measuring Attitudes Cross-Nationally (pp. 169–203). SAGE Publications, Ltd.

Sng, O., Neuberg, S. L., Varnum, M. E. W., & Kenrick, D. T. (2018). The behavioral ecology of cultural psychological variation. Psychological Review, 125(5), 714–743.

Tooby, J., & Cosmides, L. (1992). The Psychological Foundations of Culture. In J. Barkow & G. Williams (Eds.), The Adapted Mind: Evolutionary Psychology and the Generation of Culture.

Wormley, A. S., Kwon, J. Y., Barlev, M., & Varnum, M. E. W. (2022). Ecology Explains a Substantial Amount of Human Cultural Variation Around the Globe. PsyArXiv.

Wormley, A. S., Kwon, J. Y., Barlev, M., & Varnum, M. E. W. (2022). The Ecology-Culture Dataset: A new resource for investigating cultural variation. Scientific Data, 9(1), 615.

The Ecology-Culture Dataset is accessible at

The accompanying article—Wormley et al., 2022—can be accessed at