Evolution of Song Culture:
How Social Interactions Shape Song Development
Would culture resembling existing ones evolve in an island colony of naïve founders? This cannot be studied experimentally in humans; we performed the analogous experiment using socially learned birdsong. Zebra finch isolates unexposed to singing tutors during development, produce song with characteristics that differ from the wild-type song found in laboratory or natural colonies. In tutoring lineages starting from isolate founders, we quantified alterations in song across tutoring generations in two social environments: sound isolated chambers with tutor-pupil pairs, and an isolated semi-natural colony. For both tutor-pupil only and isolated colony settings, songs evolved toward the wild type in 3-4 generations. Therefore, species-typical song culture can evolve de novo. Although the progression toward wild type song culture takes place even in an impoverished environment, no innovation and invention of new syllable type were observed in a one-to-one song tutoring setting. In contrast, in a colony environment, in the presence of females, we observed invention of new syllable types across generations. To explore the role of female zebra finches (who do not sing) in the development of song culture, we compared auditory responses to songs across males and females using functional MRI. We found that isolate males show no song specific BOLD responses in auditory brain areas. In male zebra finches, the development of song-specific auditory responses required social or song learning experience during development. In contrast, isolate females showed song-specific BOLD responses similar to those observed in experienced colony raised males. Therefore, females might have an important role in the development of song culture, since they show song-specific responses prior to experience. I will present ongoing experiments in controlled social environments to test how social interactions with males and with females might affect the development of song culture across generations.
