Culture is typically viewed as consisting of traits inherited epigenetically, through social learning. However, cultural diversity has species-typical constraints, presumably of genetic origin... Zebra finch isolates, unexposed to singing males during development, produce song with characteristics that differ from the wild-type song found in laboratory11 or natural colonies. In tutoring lineages starting from isolate founders, we quantified alterations in song across tutoring generations in two social environments: tutor-pupil pairs in sound-isolated chambers and an isolated semi-natural colony. In both settings, juveniles imitated the isolate tutors but changed certain characteristics of the songs. These alterations accumulated over learning generations. Consequently, songs evolved towards the wild-type in three to four generations. Thus, species-typical song culture can appear de novo....
Here's ScienceDaily with an outline:
Scientists have known for decades that the "innate" song of an isolated songbird is different from the "learned" song of a songbird that was tutored by an adult. But where did that adult tutor's song come from? Obviously from it's own father, but where did this passed-down song originate? "This is a classic chicken-and-egg problem," says Mitra.
He hypothesized that if the song of an isolated songbird were transmitted over multiple generations, the normal wild-type song would somehow spontaneously emerge. Using what mathematicians call a "recursive equation," he came up with a mathematical model of how this might happen. This model, combining ideas from the literature on cultural evolution and quantitative genetics, tries to quantify the relative contributions of the songbird's genetic background, learning ability and environmental factors to the emergence of the cultured song.
To experimentally test his hypothesis, Mitra five years ago approached his long-time collaborator, Professor Ofer Tchernichovski, Ph.D., a songbird biologist at CCNY. Tchernichovski and his graduate student Olga Feher took up the experimental challenge, raising songbirds in soundproof boxes and collecting audio and video recordings of their subjects. Mitra and CSHL postdoctoral fellow Haibin Wang in turn analyzed these recordings, comprising a large dataset of several terabytes, which show that the innate song of an isolated bird is gradually transformed over multiple generations into a song that closely resembled the song normally found in the wild.
A hypothesis, and experiment. Perfect.
But of course this has possible implications outside of birds, as there are many organisms with culture morphs which emerge through a complex interaction between gene disposition and various environmental parameters. Consider human beings. A tabula rasa view of human nature which was common until recently in much of anthropology seemed to posit that our species could explore a nearly infinite sample space of possibilities when it comes to the range of characteristics of societies. Evolutionary psychology in the classical sense arose in the 1980s as a counterpoint to this sort of thinking, emphasizing universal and invariant behavioral and social traits which presumably have a biological basis and are genetically encoded.
Both of these extreme positions clearly do not accurately describe the dynamic reality of human cultural evolution and development. Rather than a "flat" and nearly infinite space of possibilities, or a topology of a only a few narrow stable peaks, it seems possible that human culture flows through a space with peaks, valleys, constraints and canals. To me this theoretical "middle ground" is much more in keeping with the empirical reality of the cyclical nature of many societies, as well as insights from game theory as to how complex group dynamics evolve over time.
Excellent visual. I found it so useful, I linked to you in my blog.
So IIUC, bird songs have certain characteristics that are (indirectly) genetically encoded, while still allowing for significant "cultural" variation in other respects. Isolated individuals lose these universal characteristics, but they gradually re-emerge due to genetic biases in learners over generations.
That looks an awful lot like the spontaneous transition from makeshift "pidgin" to fully-fledged, grammatically structured "creole" among humans (although recently the idea that this transition is induced by genetic factors has been contested).