Chapter 2. Areal diffusion and parallelism in drift
Shared features, and especially shared grammaticalization patterns, may result from geographic proximity, contact, and borrowing (“copying”). Related languages “will pass through the same or strikingly similar phases”: this “parallelism in drift” (Sapir 1921: 171‒172) accounts for additional similarities between related languages, even for those “long disconnected”. Parallelism in drift may also account for shared patterns of grammaticalization. The paper explores the ways in which patterns of shared grammaticalization which are demonstrably due to areal diffusion may differ from patterns which can be shown to result from parallelism in drift. To work towards an answer, we focus on the data from two different areas of substantial linguistic diversity: the Arawak languages of northwest Amazonia, and the Ndu languages of the Sepik region of New Guinea.