The Interplay of Genetic and Cultural Factors in Ongoing Language Evolution

Abstract

This chapter discusses recent advances in our understanding of the complex interplay between cultural and biological factors in language change and evolution. Three “myths” (the independence of biological and cultural evolution, a fi xed biological foundation for culture, and the cognitive uniformity of humans) are identifi ed and falsifi ed. Strong genetic biases are shown to affect language profoundly, using the example of village sign languages that emerge and complexify due to persistent high frequencies of genetic deafness in certain communities. Evidence is presented for the genetic bases of language and speech, and the extensive genetic variation within populations affecting them. Finally, it is proposed that in addition to intrapopulation variation, interpopulation differences in genetic biases that affect language and speech contribute to the emergence of linguistic diversity, through iterated cultural transmission across generations as well as communication and alignment within them. Thus, biological and cultural processes cannot be meaningfully separated when studying the cultural evolution of language. Cultural Evolution and Biological Evolution Are Two Sides of One Process This chapter is about the relationship between cultural and biological evolution, as evidenced in the domain of language. Many scholars with an interest in cultural evolution operate with a set of myths or fi ctions, tacitly holding something like the following: 1. Fiction of independence of biological and cultural evolution. Biological and cultural evolution are for practical purposes now independent processes, and despite the “curious parallels” between the diversifi cation From “Cultural Evolution: Society, Technology, Language, and Religion,” edited by Peter J. Richerson and Morten H. Christiansen. 2013. Strungmann Forum Reports, vol. 12, J. Lupp, series editor. Cambridge, MA: MIT Press. ISBN 978-0-262-01975-0. 220 S. C. Levinson and D. Dediu of species and of languages (as noted by Darwin 1871), the underlying principles are fundamentally different. 2. Fiction of a fi xed biological platform for culture. Nevertheless, on a deep and ancient timescale, the two evolutionary tracks were in fruitful interplay and coevolved a now fi xed platform for cultural liftoff: the big human brain, the language capacity, and the manual dexterity that made technology possible. 3. Fiction of the cognitive uniformity of the species. Since, generically, all humans have complex cognition, use language and make things with their hands, these capacities can be taken to be near uniform across the species: they form a constant background to cultural evolution. In contrast, this chapter advances the following propositions: 1. Cultural and biological (genetic) evolution constitute twin tracks of an evolutionary process. 2. There are two-way feedback relations between the tracks. 3. These relations are ongoing. 4. There is signifi cant variation within populations both with regard to genes and cultural variants, which supplies the “fuel” for evolutionary