Language phylogeny trumps geography in lexical semantic variation

A central aim of the cross-cultural study of linguistic structure is to find factors motivating the observed variation. Aspects of structure from phonology to lexical semantics have been explained by biological, cultural and environmental factors. We address the lexical semantics of body part terminology. There is a hypothesis that the lexical differentiation of the upper limb into "hand" and "arm" (versus a single undifferentiated term) correlates with distance from the equator. But taking into account the evolutionary perspective we show that the correlation between absolute latitude and hand-arm terminological differentiation is an artifact of the highly skewed distribution of language families. We demonstrate this with two techniques: we use bootstrap sampling by language family to investigate variation within phylogenetically independent samples of languages, and we analyze variation within large families to show that lexical semantics is better predicted by clade membership than geography