A genetic and linguistic analysis of the admixture histories of the islands of Cabo Verde.

From the 15th to the 19th century, the Trans-Atlantic Slave-Trade (TAST) influenced the genetic and cultural diversity of numerous populations. We explore genomic and linguistic data from the nine islands of Cabo Verde, the earliest European colony of the era in Africa, a major Slave-Trade platform between the 16th and 19th centuries, and a previously uninhabited location ideal for investigating early admixture events between Europeans and Africans. Using local-ancestry inference approaches, we find that genetic admixture in Cabo Verde occurred primarily between Iberian and certain Senegambian populations, although forced and voluntary migrations to the archipelago involved numerous other populations. Inter-individual genetic and linguistic variation recapitulates the geographic distribution of individuals' birth-places across Cabo Verdean islands, following an isolation-by-distance model with reduced genetic and linguistic effective dispersals within the archipelago, and suggesting that Kriolu language variants have developed together with genetic divergences at very reduced geographical scales. Furthermore, based on approximate bayesian computation inferences of highly complex admixture histories, we find that admixture occurred early on each island, long before the 18th-century massive TAST deportations triggered by the expansion of the plantation economy in Africa and the Americas, and after this era mostly during the abolition of the TAST and of slavery in European colonial empires. Our results illustrate how shifting socio-cultural relationships between enslaved and non-enslaved communities during and after the TAST, shaped enslaved-African descendants' genomic diversity and structure on both sides of the Atlantic.

Testing the effects of congruence in adult multilingual acquisition with implications for creole genesis.

Linguists from across sub-disciplines have noted that congruence (i.e., form-function mapping) across languages in contact seems to affect acquisition and play a role in language emergence (e.g. Creole genesis). However, because congruence is often confounded with other variables (e.g., frequency, language type, speakers' proficiency levels, perceptual salience, semantic transparency), it remains unclear whether congruence per se benefits learners. In this paper, we provide an experimental test of the effects of congruence on acquisition through an artificial language-learning experiment involving English (L1) and two artificial languages (Flugerdu and Zamperese). English-speakers who identified as "native" (i.e., first-language) speakers (N = 163) were randomly assigned to one of four conditions, varying which of the three languages expressed negation with congruent forms: all three languages; only Flugerdu and Zamperese; only English and Flugerdu; or none. Our findings show that participants better acquired the negation morpheme when the form was congruent with negation in English but not when the two artificial languages alone shared a congruent form. We likewise found unanticipated spillover effects in which participants better acquired the vocabulary and grammar of the artificial languages when all three languages had congruent negation forms. These findings provide insight into the effects of congruence on language acquisition in multilingual environments and Creole language formation.

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

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.