by Patience Epps.
Read her chapter here. Despite its focus on non-Australian languages, those interested in Australian topics might find some of what Dr. Epps has to say very interesting. The following is a selection from its first section:
The Amazon basin is one of the most linguistically diverse regions on earth. With some 300 indigenous languages corresponding to over 50 distinct lineages, the diversity of language families in Amazonia is some ten times higher than that of Eurasia and Africa, and is rivalled only by New Guinea.
Explaining these variable patterns of diversity poses a major challenge to scholars of human prehistory. Since South America was the last continent to have undergone extensive human settlement, its linguistic diversity cannot be linked straightforwardly to time-depth of habitation (cf. Nichols 1990, Nettle 1999). Geographic factors are also not an obvious explanation, since South American diversity is concentrated in the lowlands, where natural obstacles are few (both rivers and interfluvial zones are as likely to serve as conduits as they are barriers; cf. Nichols 1992). Nor does an appeal to agriculture as a major reason for language spread provide a clear solution; a comparison of the Amazonian linguistic patchwork (where virtually all groups practice at least small-scale agriculture) to the far-reaching spread of Pama-Nyungan hunter-gatherers in Australia indicates that agriculture is in itself neither a necessary nor a sufficient condition for language spread, although it may be implicated in some cases (cf. Bellwood 2001, Heggarty & Beresford-Jones 2010). Continent-internal linguistic distributions present additional puzzles, most notably relating to the concentration of diversity in the west (see e.g. Dahl et al. 2011, who suggests a correlation with initial migration routes), and the non-contiguous distributions of the few language families that are geographically widespread (see e.g. Hornborg 2005 and the papers by Walker and Heckenberger, this volume, on the Arawak diaspora).