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 mine. 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.
- Do house finches have song dialects? We are reanalyzing the song data used in Prof. Mundinger’s 1975 paper using a more quantitative computational approach. We need to (1) code house finch song syllables just like you would code our own alphabet to make a secret code language (for example A=1, B=2, and so on), and then let Elliot run his fancy computer program STRUCTURE on it to see whether the bird’s song “languages” naturally divide into different dialects in different geographical areas. The investigation of dialects or distinct cultural categories has never been assessed quantitatively, to my knowledge, for any organism’s cultural traits, including humans.
- Deciphering house finch songs. What is the house finch lexicon or vocabulary? How many syllables (words) do they have? Does this differ from individual to individual in the same place? How many songs do we need in order to get an individual’s whole repertoire? Are different syllables or song types used in different situations? Can syllables and songs be quantitatively divided into types as human words in a language can, and has been assumed for birds, or do they vary more continuously like musical phrases do? To do this we need first to analyze the syllables to see if they are categorical or continuous. If they are at all categorical, we need to create a house finch Rosetta Stone—an arrangement of syllables next to an arrangement of codes. All of this requires recording a few males for a very long time. So far, lexicons for bird songs and human languages have only been created subjectively.
- How do house finch songs vary spatially? How do songs change as you move from place to place—whether next door, down the street, next town, or miles away? We are concentrating on Long Island currently, because this is where the birds were introduced originally, and so it forms the root of a tree that has since branched now all over the Eastern United States. With a good coverage of this area we can address questions like the boundaries and extents of dialects (following project #1), whether there are differences in different habitats such as along urban/rural or coastline/interior gradients, and we can even infer patterns of divergence from the known introduction spot just east of Brooklyn in in the southwest part of the island. This requires getting the recordings of many males over a broad geographical area, focusing perhaps on Long Island but for the longer term spreading out over the entire population. We will be using the quantitative analysis developed for project 1, and the coding developed in project 2, to understand this spatial variation.
- How have house finch songs diverged over time? We have recordings from the original source population in California from around 1980, and from the introduced population in New York from the late 1960s and early 1970s. We are also recording them now in New York and plan do so in California as well. With this data we’ll be able to address how the songs culturally evolved over this 70 year period, both within populations (especially in New York), and between populations. In fact we can infer how the songs were in California 70 years ago, see how they had diverged in both populations by 35 years ago, and now see where they stand today. To do this we need recordings of whole bird repertoires (how many songs are needed for this will be determined by project 2) in certain key areas, especially those locations for which we have older recordings. See the attached figure to appreciate this as well as the longer term goal of charting the cultural evolution of this species over its entire range, something that has never been done for any species.