The typology and diachrony of higher numerals in Indo-European: a phylogenetic comparative study

Numerals have fascinated and mystified linguists, mathematicians and lay persons alike for centuries. The productive use of numerals (in languages where this happens) exploits recursivity to give rise to what we call the ‘the number line’. While the smaller numerals 1–10 have enjoyed intense scrutiny, the typological study of the formation of the higher numerals has received comparatively less attention. This article contains a comprehensive typological account of how languages in the Indo-European language family code numerals beyond 10 (10–99, 100s, 1,000s), the morphemes involved, and how these are ordered. We use this dataset from eighty-one Indo-European languages with phylogenetic comparative methods to propose diachronic reconstructions of these patterns in the Proto-Indo-European language. Our findings indicate that small numerals (11–19) show the widest cross-linguistic variation, and that higher numerals exhibit more consistency in both component parts and their ordering. Additionally, we show statistical evidence of correlations between the ordering of base and atom morphemes and other word order patterns (noun-postposition, noun-genitive, and verb-object order).