Cultural Lability: Insights from Birdsong

Rates of evolutionary change and their underlying causes are important features of evolving traits in general, but the tempo of cultural evolution in particular has been scrutinized in less detail. Studies of socially learned birdsong provide arguably the most diverse empirical accounts of the dynamics and drivers of cultural evolutionary rate in nonhuman animals. We therefore provide the first synthesis of the birdsong literature wholly through the lens of the tempo of cultural change, which we term “cultural lability.” We first explore what is known about the effects of demographic variables on cultural lability in birdsong, touching on their functional implications and supplementing our discussions with case studies of well-documented systems. We then more closely examine the relationship between cultural lability and function, turning our attention to birdsong systems in which the components of a cultural trait are evolving at independent rates. We introduce the term “cultural asynchrony” to describe the diverse degrees of lability that exist among traits within a single cultural system. We conclude by distilling our findings into broad patterns in the behavior of socially learned birdsong, and drawing from recent literature in a variety of disciplines to emphasize novel frameworks in which cultural evolution and lability might be understood.