Language Evolution and Computation Bibliography

Recently there has been a movement in the social sciences to apply theories and methods developed originally in evolutionary biology to understand human behavior and cultural change. In this article, I highlight an ever growing branch of this research that analyzes cultural data using a suite of techniques based on evolutionary trees. These phylogenetic methods fall into two categories: (a) “tree-building” that is, inferring the historical relationships between units, and (b) comparative analyses that is, mapping other traits onto the tips of these trees to make inferences about trait evolution. Using lexical data I infer the phylogenetic relationships between 82 Indo-European languages. The estimated divergence time of these languages agrees with earlier studies in supporting a hypothesis that places the homeland of the Indo-Europeans somewhere in Anatolia 8000-9500 BP. Using data from Austronesian-speaking societies I give examples of the use of comparative methods to (i) infer the system of land tenure in ancestral societies, (ii) examine the ecological correlates of violence in the Polynesian and Micronesian societies, and (iii) test hypotheses about the mode and tempo of sociopolitical evolution. I examine future areas of cultural phylogenetic research in the evolutionary social sciences and argue that the kinds of studies introduced in this article hold the potential for fruitful collaborations between cultural phylogeneticists and cross-cultural researchers.

There is disagreement about the routes taken by populations speaking Bantu languages as they expanded to cover much of sub-Saharan Africa. Here, we build phylogenetic trees of Bantu languages and map them onto geographical space in order to assess the likely pathway of expansion and test between dispersal scenarios. The results clearly support a scenario in which groups first moved south through the rainforest from a homeland somewhere near the Nigeria–Cameroon border. Emerging on the south side of the rainforest, one branch moved south and west. Another branch moved towards the Great Lakes, eventually giving rise to the monophyletic clade of East Bantu languages that inhabit East and Southeastern Africa. These phylogenies also reveal information about more general processes involved in the diversification of human populations into distinct ethnolinguistic groups. Our study reveals that Bantu languages show a latitudinal gradient in covering greater areas with increasing distance from the equator. Analyses suggest that this pattern reflects a true ecological relationship rather than merely being an artefact of shared history. The study shows how a phylogeographic approach can address questions relating to the specific histories of certain groups, as well as general cultural evolutionary processes.

There is disagreement about whether human political evolution has proceeded through a sequence of incremental increases in complexity, or whether larger, non-sequential increases have occurred. The extent to which societies have decreased in complexity is also unclear. These debates have continued largely in the absence of rigorous, quantitative tests. We evaluated six competing models of political evolution in Austronesian-speaking societies using phylogenetic methods. Here we show that in the best-fitting model political complexity rises and falls in a sequence of small steps. This is closely followed by another model in which increases are sequential but decreases can be either sequential or in bigger drops. The results indicate that large, non-sequential jumps in political complexity have not occurred during the evolutionary history of these societies. This suggests that, despite the numerous contingent pathways of human history, there are regularities in cultural evolution that can be detected using computational phylogenetic methods.

Phylogenetic methods have recently been applied to studies of cultural evolution. However, it has been claimed that the large amount of horizontal transmission that sometimes occurs between cultural groups invalidates the use of these methods. Here, we use a natural model of linguistic evolution to simulate borrowing between languages. The results show that tree topologies constructed with Bayesian phylogenetic methods are robust to realistic levels of borrowing. Inferences about divergence dates are slightly less robust and show a tendency to underestimate dates. Our results demonstrate that realistic levels of reticulation between cultures do not invalidate a phylogenetic approach to cultural and linguistic evolution.