Parallel Trajectories of Genetic and Linguistic Admixture in a Genetically Admixed Creole Population

Summary

Joint analyses of genes and languages, both of which are transmitted in populations by descent with modification—genes vertically by Mendel's laws, language via combinations of vertical, oblique, and horizontal processes [1–4]—provide an informative approach for human evolutionary studies [5–10]. Although gene–language analyses have employed extensive data on individual genetic variation [11–23], their linguistic data have not considered corresponding long-recognized [24] variability in individual speech patterns, or idiolects. Genetically admixed populations that speak creole languages show high genetic and idiolectal variation—genetic variation owing to heterogeneity in ancestry within admixed groups [25, 26] and idiolectal variation owing to recent language formation from differentiated sources [27–31]. To examine cotransmission of genetic and linguistic variation within populations, we collected genetic markers and speech recordings in the admixed creole-speaking population of Cape Verde, whose Kriolu language traces to West African languages and Portuguese [29, 32–35] and whose genetic ancestry has individual variation in European and continental African contributions [36–39]. In parallel with the combined Portuguese and West African origin of Kriolu, we find that genetic admixture in Cape Verde varies on an axis separating Iberian and Senegambian populations. We observe, analogously to vertical genetic transmission, transmission of idiolect from parents to offspring, as idiolect is predicted by parental birthplace, even after controlling for shared parent–child birthplaces. Further, African genetic admixture correlates with an index tabulating idiolectal features with likely African origins. These results suggest that Cape Verdean genetic and linguistic admixture have followed parallel evolutionary trajectories, with cotransmission of genetic and linguistic variation.