How Cultural Evolution Generates the Global Variation of Human Minds

How Cultural Evolution Generates the Global Variation of Human Minds
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What is culture? If you search for the meaning of this word, you will most likely come across a list. For example, you might learn that culture consists of the art, clothing, cuisine, language, skills, technology, family structure, communal norms, religious practices, and worldview of a group of people. This itemizing The approach to the concept of culture is unsatisfactory, in part because people will always disagree about what to include in the list. But more importantly, culture is more than just a catalog of things.

At the core of a peach is its capacity for regeneration.

Source: GerdSchiffler/Pixabay

Culture as a regenerative cycle

Culture is a bit like a peach. People like peaches for their flesh; few get excited about the pit. But the pit is of course the seed that regenerates the fruit. Although the juicy flesh gets all the attention, at the literal core of the peach is its capacity for regeneration.

The same is true for culture. The outward manifestations of culture—the enchanting artifacts, the photogenic rituals, and the delectable cuisines—tend to get all the attention, but at the core of culture is a cycle of regeneration. Artifacts, rituals, and cuisines are more than just interesting: they have been continually reproduced over generations, accumulating new features along the way. In fact, most cultural items could not be as interesting as they are if they had not undergone this regenerative process over many iterations. It’s possible to invent something remarkable within a single generation, but this is the exception rather than the rule.

For most animal species, reliable transmission of cultural traits across generations is challenging. Even if a non-cultural animal comes up with a remarkable behavioral innovation, the skill will die with its innovator as the population is unable to sustain it over time. Creativity quickly flickers out in the absence of efficient cultural transmission.

But humans are a notable exception. We instruct, we enforce, we codify, we comply, we conform, we imitate—such forms of cultural transmission are where we excel. These actions come so naturally to us that we rarely give it much thought, but the vigor and proficiency with which we execute these “file-transfer protocols” are unparalleled in the animal kingdom.

When innovations can be sustained, a kind of market dynamic emerges, where some cultural traits thrive at the expense of others. This system of regeneration, innovation, and selection of cultural traits is known as cultural evolution, due to its structural similarities with genetic evolution. Cultural and genetic evolution differ in interesting ways as well, but the analytic methods used to study genetic evolution have been particularly useful for dissecting and modeling the organization of culture.

Culture is conceptualized here not as a list of things in the world, but rather as a mode of transmission. If some trait X can be learned from the social environment, and then be further passed onto others in the same way, then X is undergoing iterated cultural transmission. The criterion for culture is participation in this regenerative cycle. The important question for culture is not what, but how. By this definition, culture is not limited to just visible and tangible things.

Cultural transmission of human psychology

Culture is not just “out there” in the world, it also permeates our innermost faculties. It’s not just the shape of a tool or the sound of a word—cultural transmission can disseminate psychological traits as well.

One piece of evidence for the cultural transmission of human psychology is the cultural diversity of human psychology. Cultural scientists have revealed global variation in mental traits ranging from low-level visual perception (Nisbett & Miyamoto, 2005) and memory structure (Wang, 2021) to numeric chunking (Domahs et al., 2010), spatial coding (Majid et al. , 2004), economic decision-making (Henrich et al., 2005), and moral judgment (Barrett et al., 2016). Such studies make it plain that human minds vary across societies, even for traits that were long assumed to be universal across our species.

But even these findings are still limited, due to the vast majority of psychological studies being conducted with university students in North America and Western Europe. If we were able to sample data more broadly across the globe, our understanding of the human mind would no doubt become better adapted to the reality of psychological diversity.

Some of this variation can be attributed to genes, but there is mounting evidence suggesting a sizeable role for cultural transmission. In some cases, the genetic contribution may be systematically overestimated at the expense of culture, due to limitations and biases in the measurement of genetic effects. My colleagues and I explore this topic in a forthcoming paper (Uchiyama, Spicer, & Muthukrishna, in press; also see preprint), and I plan to discuss it here again in more depth.

Decentralized production of future minds

We know that minds are shaped by experience, but it’s rare to talk about the collective and historical forces that shape experience itself. For comparison, think of the full range of variation of some cultural trait, like the species of fish used for sushi, or the pronunciation of the English word forty. Distributions of these traits have been shaped by cultural evolutionary dynamics that span many societies and unfold over a great many generations. Their production precedes your existence: you are born into a food culture and a dialect.

Likewise for minds. It’s not just the innate neural hardware or individual learning alone that makes you who you are. Your mind is shaped by neurodevelopmental inputs, and these inputs are in turn shaped by cultural evolution, at a rate that is orders of magnitude faster than genetic evolution. The cultural forces that guide the trajectory of your brain development have been undergoing rapid, decentralized R&D (research and development) long before the sprouting of your first neuron. You are born into a crowdsourced mind; This is a crucial difference in brain development between humans and other animals.

Psychological inheritance does not diminish the role of agency and self-determination. In fact, agency and self-determination are precisely what are needed in the regenerative cycle of cultural evolution. Like its genetic counterpart, cultural evolution requires the continual injection of novel elements for it to respond fluidly to changes in its environment (a large part of which are changes driven by cultural evolution itself, thus supporting positive feedback loops). The regular emergence of psychological variation supports this adaptability.

When we invent a new way of seeing things, a new sense of social connectedness, a new stance toward life, or a new emotion, we leave our mark on the cultural history of human psychology. In exceptional cases, our psychological innovations are widely reproduced by posterity and can transform societies.

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