Socially learned traits can accumulate over time. Things we learn from each other can be passed on and added to. This process, which is a commonplace in humans is being increasingly discovered in other animals, especially in primate food finding or preparation and in bird song. Cultural evolution is as fascinating as genetic evolution in terms of process, and in its pattern it is sometimes even more intriguing because it is a wild ride-- it happens at the speed of learning instead of the speed of reproduction!
Nevertheless, I am wary of the term "cultural evolution". Yet, how can a term be controversial when the process it refers to is totally accepted? In other words, there probably isn't a single person on the face of the earth who understands the concept of cultural evolution and doesn't agree that it happens all the time. Even creationists would accept it, which means that it must be ridiculously obvious and practically self-evident. And it is. Cultures do not stay the same. They change. Ways of preparing food, pottery styles, accents, acceptable behavior, fashionable dress and accessories, colors of possessions, music and other arts, cars and other symbols of personality and wealth, all of them are subject to incessant wandering... modification... evolution. That's all that is meant by the term, when we get right down to it. And yet, like "sociobiology" once did, the term "cultural evolution" seems to pigeonhole the user in one of various ways that leaves a bad taste in the mouth of just about everyone else who is interested in the very same thing but doesn't call it "cultural evolution". For biologists, for instance, the term often either suggests a particular approach (mathematical theory bereft of knowledge of the real world), or else a simplistic yen for troublesome analogies (memes with genes), a lack of appreciation for natural selection (assumptions of selective neutrality), or, finally, a misleading use of the term "evolution", which should be reserved for genetic change. It so happens that I sympathize with all four of these sneers, and yet I still have nothing better than "cultural evolution" to call this interest of ours. I won't defend it here except to say that there is nothing in the study of cultural evolution that requires theory to ignore data, that requires us to use the simplistic and misleading concept of a meme, or that requires us to exclude natural selection or the influence of our (or any species') heritage of genetic evolutionary adaptation; and the word "evolution" is broadly used in our culture for things other than genetic change and so I am content to contrast cultural with genetic or organic evolution. For those in the social sciences the term might suggest genetic determinism or progress, but both of these are just silly misunderstandings since none of the professional literature even hints at either of these. My opinion, without qualification, is that cultural anthropologists, culture theorists, sociologists, ethnographers, archaeologists, social psychologists, political scientists, linguists, and historians are actually students of human cultural evolution, whether they realize it or not.
I study cultural evolution in humans and in songbirds, the two kinds of organisms in which it is most well known. I say "known" rather than "understood" because although we have some understanding of it in songbirds, our understanding of where culture goes and why in humans is comparatively embryonic.
Our cultural evolution study systems
Many birds learn their songs, passing them from generation to generation with various interesting mistakes and innovations along the way... yet they are short-lived enough for us to follow this trail of the transmission of socially learned traits! This combination of features makes bird song the number one animal model system for the study of cultural evolution. Our lab is studying the cultural evolution of a few different species of birds, but the main project (indeed, the main project of the lab as a whole) is house finch song.
Cultural evolution in birds
My students are continually asking new questions about cultural evolution, but at this point our main questions are four:
Cultural evolution in humans
The change and accumulation of human ideas and their underlying causes comprise one of the most longstanding and profound topics of human thought and research. Several intensive research programs have emerged over the last forty years, devoted to the study of these changes, all under the banner of cultural evolution. The main goal of my research in this area-- which has only just begun-- is to assess and promote the integration of this promising but disparate young science. Borrowing inspiration from biological evolution, where such a synthesis has already taken place, the overall objectives are to (1) unify cultural evolution conceptually; (2) foster the testing of predictions through quantitative analysis; and (3) integrate previously isolated empirical fields under a common framework.
Broadly philosophical work is needed in order organize the discipline, assess the current state of knowledge about cultural evolution, develop a common vocabulary, and extract testable hypotheses from the controversies. Several empirical studies are in the works as well, that represent collaborations between philosophy, psychology, archaeology, anthropology, and biology. I am still working on obtaining funding for these projects.