Where Do Cultural Differences Come From?

Since antiquity, people have speculated about why it is that people in different parts of the world have different customs, rules, habits, and psychological tendencies. Indeed, if you’ve traveled outside of the country you are born in, you’ve probably noticed a host of differences, not only in the languages people speak and the food they eat but also in how people express their feelings, how open they are to trying new things, and the rules they have for behavior.

In more recent times, psychologists and anthropologists have proposed a number of theories for why these kinds of differences exist. For example, some have argued that the type of crops that were historically grown in a region helps explain cultural variation in individualism (Talhelm et al., 2014). Others have pointed to the historical role played by institutions like the early Catholic church in shaping variation across societies in conformity and creativity (Henrich, 2020). Yet other accounts emphasize how historical differences in philosophy between ancient Greece and ancient China may help us to understand contemporary differences between Western and East Asian cultures in reasoning and other habits of thinking (Nisbett, 2004).

The Role of Ecology

But there’s another answer for why cultural differences exist—namely, that in different parts of the world, we are exposed to different physical and social environments, or ecologies (Sng, Neuberg, Varnum, & Kenrick, 2018). To help understand why, we can think about jukeboxes. We can think about jukeboxes containing roughly the same set of songs (especially in the era of internet-connected ones), but placed in different locations. These jukeboxes are more likely to play some songs in one place than another (Barkow, Toobey, & Cosmides, 1992). Outlaw country songs will be played more often at a honkey tonk in rural Texas than in a bar in inner-city Detroit.

If we substitute people for jukeboxes, and behavioral and cognitive adaptations for songs, then we have a decent analogy for how environments with different sets of ecological conditions may “evoke” different patterns of cultural responses. In this view, cultures in different parts of the world may have not only different tastes but also different practices, patterns of behavior, and ways of thinking because individuals in places with similar environments respond to them in the same adaptive ways. And just as a jukebox doesn’t learn how to compose a David Allen Coe song or a 50 Cent song, nor do humans have to learn many of their psychological and behavioral responses; rather like a jukebox, we come with many of them pre-programmed, so to speak.

In a similar vein, Oliver Sng and colleagues (2018) have proposed that humans, like many other animals, possess what they term “adaptive phenotypic plasticity”—meaning, that “individuals with the same genes may exhibit different traits under different environmental conditions...[as] a result of mechanisms that have evolved to be sensitive to environmental changes.” Why might this be the case? Sng argues that “if in different environments some behaviors are more biologically adaptive than others, and organisms have regularly encountered varying environments (across time or location) in their ancestral history, then natural selection should favor the evolution of environmentally sensitive flexibilities.” Given that humans' ancestral environments did in fact vary in terms of features like infectious disease threat, resource availability, and climate, then we should expect that humans should have evolved a suite of adaptive behavioral and psychological responses that are sensitive to variations in these conditions and can be triggered by them.

If cultural variation is driven (at least in part) by ecological conditions, as the evoked culture and adaptive phenotypic plasticity frameworks suggest, then we would expect that there should be similarities in the behaviors or psychological tendencies observed among human groups sharing similar ecologies. This way of thinking also suggests that parallels would be found between humans and other animals inhabiting the same places.

What’s the Evidence?

A recent analysis by Barsbai and colleagues (2021) suggests that this is, in fact, the case. Looking at 339 small-scale human societies, other mammals, and birds in locales around the globe, Barsbai found striking correlations between a variety of behaviors across these very different species. In places where food hoarding was common among human cultural groups, so too was it among other mammals and birds. In places where humans had to travel longer distances to forage for food, again, other mammals and birds also had to do so. The researchers found similar correlations across species in the age of first sexual reproduction, and in places where human males provided more investment in and care for their children, there were a greater number of other animal species in which males helped care for their offspring.

Even more strikingly, this analysis revealed a correlation between the presence of strong class hierarchies—in locales where human groups had social class systems, a greater proportion of other mammals and birds also showed evidence of status hierarchy, with some dominant animals breeding and others playing the role of helpers. Consistent with the argument that ecology is driving these similarities, the strength of this correlation across species declined when controlling for ecological markers.

And there are other fascinating parallels that have been uncovered when it comes to ecology's effects on humans and our relatives in the animal kingdom. It turns out that human cultural diversity is correlated with species diversity. In places where a greater variety of languages are spoken, a common proxy for cultural diversity in a given region, we also reliably see a greater variety of nonhuman animal species (Pagel & Mace, 2004). Further, the same principles that govern species diversity appear to be related to human cultural diversity as well (Hamilton, Walker, & Kempes, 2020).

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Also consistent with the view that ecology helps explain human cultural differences are the results of a new study that explored the links between nine key ecological variables (like rainfall, temperature, population density, and infectious disease) and 66 cultural variables for dozens of societies around the world (Wormley, Kwon, Barlev, & Varnum, 2023). In this study, we found that even after controlling for potential confounds, ecology explained a sizable amount of the variation in cultural tendencies around the world; roughly 16 percent for current ecological conditions and around 20 percent for the historical means of those conditions. Although 16 to 20 percent may not sound like a lot, in fact, this is several times larger than the average amount of the outcome explained in studies in our field, social psychology (Gignac & Szorodori, 2016). This adds to a growing body of work documenting links between specific ecological features and specific cultural patterns and suggests that ecology may be a key driver of human cultural diversity.

Conclusion

We don’t typically think about things like temperature or how densely populated a place is when we wonder why societies differ in the ways they do. Yet a growing body of evidence suggests that these kinds of factors may play a key role in explaining where cultural differences come from.