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There has been a rapid increase in the use of phylogenetic methods to study the evolution of languages and culture. Languages fit a tree model of evolution well, at least in their basic vocabulary, challenging the view that blending, or admixture among neighbouring groups, was predominant in cultural history. Here, we argue that we can use language trees to test hypotheses about not only cultural history and diversification, but also bio-cultural adaptation. Phylogenetic comparative methods take account of the non-independence of cultures (Galton's problem), which can cause spurious statistical associations in comparative analyses. Advances in phylogenetic methods offer new possibilities for the analysis of cultural evolution, including estimating the rate of evolution and the direction of coevolutionary change of traits on the tree. They also enable phylogenetic uncertainty to be incorporated into the analyses, so that one does not have to treat phylogenetic trees as if they were known without error.

Phylogenetic approaches to linguistic and cultural evolution promise to increase our understanding of human prehistory and adaptation. Among the many recent studies applying phylogenetic methods to languages and other aspects of cultural variation, two subfields stand out in particular: (i) inferring phylogenies of language families and cultural artefacts; and (ii) testing comparative hypotheses about human bio-cultural evolution, which refers to the ways in which humans adapt, biologically and culturally, to their diverse environments. Whereas much previous work in cultural evolution was predominantly theoretical in focus [1], the newly emerging field of cultural phylogenetic analysis is strongly empirical. An unexpected result of recent phylogenetic analyses of languages is just how well their histories fit a branching tree model 2, 3 and 4, at least in their basic vocabulary. This challenges the view, dominant within archaeology and anthropology throughout the second half of the 20th century, that blending processes were predominant in cultural history. Here, we argue that language trees can be used to test hypotheses about not only cultural history and diversification, but also bio-cultural adaptation, using phylogenetic comparative methods. Comparative analysis is of primary importance in scientific anthropology, partly because opportunities for experimentation are limited, but also because humans show such a remarkable range of cross-cultural variation.

Evolutionary ecology and comparative biology bring a useful toolkit of statistical methods to cultural evolutionary studies. There is a strong tradition of comparative studies in linguistics, archaeology and anthropology 50, 51 and 52, which have informed much of our knowledge of both human migration and adaptation, but statistical methods are often viewed with suspicion. Anthropologists are fond of pointing out the complexity of cultural systems, and either using it as an excuse to not ask precise questions, or to question the validity of the assumptions of the models being used. But questions about the prevalence of horizontal transmission, or how long cultures endure, do not make sense if no phylogeny is implied. New methods are rendering many of the old debates irrelevant, as the influence of phylogeny on the data distribution can now be tested, and phylogenetic uncertainty can also be incorporated. Within the phylogenetic framework, anthropologists are now asking – and sometimes answering – such questions empirically, and with a new level of precision.