Quantifying uncertainty in the phylogenetics of australian numeral systems

Abstract

Researchers have long been interested in the evolution of culture and theways in which change in cultural systems can be reconstructed and tracked.Within the realm of language, these questions are increasingly investigatedwith Bayesian phylogenetic methods. However, such work in cultural phylogeneticscould be improved by more explicit quantification of reconstructionand transition probabilities. We apply such methods to numerals in thelanguages of Australia. As a large phylogeny with almost universal ‘lowlimit’systems, Australian languages are ideal for investigating numeralchange over time. We reconstruct the most likely extent of the system at theroot and use that information to explore the ways numerals evolve. We showthat these systems do not increment serially, but most commonly vary theirupper limits between 3 and 5. While there is evidence for rapid system elaborationbeyond the lower limits, languages lose numerals as well as gain them.We investigate the ways larger numerals build on smaller bases, and showthat there is a general tendency to both gain and replace 4 by combining 2+2 (rather than inventing a new unanalysable word ‘four’). We develop aseries of methods for quantifying and visualizing the results.