There’s an edition of the Web comic Saturday Morning Breakfast Cereal in which one of the recurring characters asks God: “What’s the deal with the platypus?

As the character goes on to explain, the platypus is an animal of contradiction. It’s got a cloaca and beak, like a bird, but it also has fur and lives in the water, like a mammal. So the question is a good one, from a comparative point of view—but God is having none of it. “You’re a talking ape. You’re like 10 seconds out of the trees and you drive around in giant metal boxes like it’s perfectly normal animal behavior. You get your food from a giant box-shaped cave built by other talking apes, none of whom knows where the food came from. Your dominant form of communication is entering patterns of squiggles into a mechanical brain and sending it to other mechanical brains! And you’re weirded out by a mammal with a beak? You’re weird.”

Weird we are. And look at the things God uses to make this point: languages, cars, shops, writing, computers—cultural, all of them. We are not born with any of this nor do we have the capacity to invent them alone. Such beliefs, behaviors, knowledge and artifacts are not part of the human phenotype but are instead the consequence of an enormous crisscrossing mesh of causes and consequences that stretches back through time, to the very beginning of human history. Any science of the human must grapple with this process and its consequences.

But what sort of science would that be? Many anthropologists, recognizing the important truth that humans are deeply, inevitably embedded in an individual cultural context, have concluded any science of human culture is either impossible, undesirable or both. Psychologists, for their part, have an almost dogmatic commitment to the tools and trappings of the mature sciences: objective measurement, controlled experimentation, model systems and the like. But it is hard to apply such tools to something as chaotic and amorphous as culture.

Over the past 30 or so years, advocates of a research agenda known as cultural epidemiology have developed arguments that a natural science of culture should be epidemiological. The word is a concatenation of Greek origin: epi (upon, among), demos (people, district) and logos (study, word, discourse). Epidemiology, then, is the study of what is upon the people. The word is presently mostly used in medical contexts but its historical meaning is not restricted to that domain; and indeed, we often use the language of epidemiology to talk about cultural phenomena, particularly those we consider harmful. We sometimes talk, for instance, about cultural “epidemics”: of, say, knife crime. Cultural commentators describe nationalism, political cynicism and other such passions as “pathogens,” and the idea we can be “inoculated” against particular attitudes and beliefs has a long history in social psychology.

Belief in the supernatural, marriage rituals, the rules of chess, legal norms, tulip mania, writing, technological knowledge, and countless other examples too: all are epi demos. Good or bad, they , exploit susceptibilities of the mind, just as infectious diseases exploit susceptibilities of the body.

There are of course many differences between the two domains. Probably the most important difference is in the mechanics of how items spread through a population. Ideas and other cultural phenomena are not ‘transmitted’ between individuals, not strictly speaking. They are, instead, generated and constructed anew by each mind. It just happens that different minds often generate similar ideas.

At the same time, diseases and ideas are both upon the people, so to speak, and there may be a great deal to be learned from the equivalence. As part of the medical sciences, pathology and epidemiology are joined at the scientific hip, as they rightly should be, for each is highly relevant to the other. In other words, the study of how and why individual bodies become infected (pathology) benefits enormously from the evidence and insights of how and why diseases spread through populations (epidemiology). Vice versa too. Cultural epidemiologists believe that psychology and anthropology should be similarly conjoined, as the study of belief and behavior in individuals (psychology) and in populations (anthropology).

Many unanswered questions remain, of course, but the outline of the epidemiological picture has now taken shape. We know something about why human minds (and not platypus minds) are highly prone to culture, and we also know something about how some cultural items, and not others, morph and scale up over time to become stable and widespread in a population. To become, in other words, upon the people.

These insights are being used to investigate and understand a wide range of cultural domains. Perhaps the most well-known (but certainly not the only example) is the finding gods and other supernatural entities tend to have the character of being minimally counterintuitive. Supernatural beings have to have some qualities that distinguish them from ordinary humans, but they are otherwise quite familiar. The god in Saturday Morning Breakfast Cereal is omniscient (that’s why the character asks the difficult question about the platypus) but it also speaks English. Being counterintuitive makes such ideas attention-gabbing, and being only minimally so makes them easy to represent and remember. Put these two properties together and you have something that’s just as appealing to the mind as the common cold is infectious to the body.