De novo establishment of wild-type song culture in the zebra finch

Culture is typically viewed as consisting of traits inherited epigenetically, through social learning. However, cultural diversity has species-typical constraints(1), presumably of genetic origin. A celebrated, if contentious, example is whether a universal grammar constrains syntactic diversity in human languages(2). Oscine songbirds exhibit song learning and provide biologically tractable models of culture: members of a species show individual variation in song(3) and geographically separated groups have local song dialects(4,5). Different species exhibit distinct song cultures(6,7), suggestive of genetic constraints(8,9). Without such constraints, innovations and copying errors should cause unbounded variation over multiple generations or geographical distance, contrary to observations(9). Here we report an experiment designed to determine whether wild-type song culture might emerge over multiple generations in an isolated colony founded by isolates, and, if so, how this might happen and what type of social environment is required(10). Zebra finch isolates, unexposed to singing males during development, produce song with characteristics that differ from the wild-type song found in laboratory(11) 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. Our study has parallels with language change and evolution(12-14). In analogy to models in quantitative genetics(15,16), we model song culture as a multigenerational phenotype partly encoded genetically in an isolate founding population, influenced by environmental variables and taking multiple generations to emerge.