Abstract
Most of the world's languages have numeral systems with a decimal base, but in some areas, such systems are rare. This article focuses on languages with either restricted numeral systems or systems featuring compositional anchors that are not bases, examining how they are used in the creation of non-atomic numerals. We investigate anchor choice from an explicitly diachronic perspective by modelling it on phylogenetic trees for language families from two areas: northern lowland South America (Arawakan, Pano-Tacanan, Tucanoan and Tupian) and Papuan languages of New Guinea (Nuclear Torricelli, Nuclear Trans New Guinea, Ramu and Sepik). We find languages with restricted numeral systems lacking anchors, as well as systems with anchor 2 or 5. Phylogenetic analyses suggest that the proto-languages of these families likely had restricted or anchor 2 systems, with shifts to anchor 5 occurring in specific groups, indicating some time depth, although statistical power is limited by small family sizes. Further research should study linguistic systems alongside cultural counting practices, reconstruct both linguistic forms and cultural practices and model the impact of contact, especially given the global dominance of decimal systems.This article is part of the theme issue 'A solid base for scaling up: the structure of numeration systems'.