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The CECD is an AHRC funded research group dedicated to examining the evolutionary underpinnings of human cultural behaviour, past and present. more>

Page Title - projects
Phase 2: Theme B - Cultural and linguistic diversity: Project B001
The rate of evolution of cultural traits on phylogenies


Fiona Jordan (Evolutionary Processes in Language and Culture, Max Planck Institute for Psycholinguistics PB310)
Ruth Mace (Department of Anthropology, University College London)

PROJECT FUNDING: Cards Against Humanity
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Recent work in both anthropology and linguistics has provided evidence that much of cultural evolution is tree-like: that is, daughter cultures evolve by descent, with modification, from mother cultures. Evidence for this is particularly strong for linguistic evolution, but there is also evidence from other cultural traits, particular social structure and modes of subsistence, and a little evidence from archaeological artefacts. New phylogenetic models, devised in evolutionary biology, enable us examine the extent to which traits are vertically transmitted, the rate at which they change over time on the branches of the tree, and whether they are co-evolving. These new quantitative methods allow an entirely new method of investigation of cultural evolution in many traits that actually leave no clear trace in the archaeological record, and thus we have very little idea how dynamic they really are.

In this project we will build on work we have already done establishing linguistic phylogenies of language, and examining to what extent other cultural traits are vertically transmitted on trees, or are borrowed. We will then go on to precisely estimate rates of change of different cultural and linguistic traits. Phylogenetic models that use likelihood can be used to estimate the most likely path of evolution, given the distribution of cultural variation in extant cultures and given the tree. We will be able to examine evolutionary rates of cultural evolution on at least three cultural groups for which we have established phylogenies on the basis of linguistic data: the Indo-Europeans, the Bantu and the Pacific Islanders. Thus we will be able to compare the relative rates of cultural evolution across different peoples, and across different types of traits. Whether certain cultural traits evolve at similar rates in different parts of the world is unknown.

The original scope of the project was to compare across broad classes of cultural traits, but only kinship and subsistence traits were amenable to appropriate comparisons across the three languages families without distortion. Work focussed initially on postmarital residence, using data across 135 Austronesian and 68 Bantu languages to reconstruct the ancestral states of residence and infer the model and rates of cultural evolution. These models and rates were then compared to Indo-European analyses done by L. Fortunato. Results show lineage-specific processes with very different rates of evolution across the three families (the overall rates of change show that residence changes faster in AN > Bantu > IE), but models of change reveal similarities in the relative rates of change - losses of matrilocality occur at universally higher rates than gains (Fortunato & Jordan in press, Jordan in prep). These types of analyses are unique in cultural evolutionary work showing how we can not only reconstruct social history in the absence of archaeological evidence, but also compare formal models of culture-trait evolution across large and diverse language families.

Similar analyses were conducted on marriage payments and transfers but presentation of this work at conferences has highlighted that the data on marriage payments needs to be revisited, so this work (comparing rates and coevolutionary models across the three families) is still in preparation. A further manuscript on descent, subsistence and residence across the three families is also in preparation with an aim to submit in early 2011. R. Mace and I also revised our initial work on the mode of cultural evolution at the macro-scale (horizontal/vertical) for a paper now in press.

I further addressed rates of evolution by looking at the impact of demographic factors (population size and density) on rates of linguistic evolution in Austronesian basic vocabulary. While population density has no discernable effect, population size has a small but robust correlation with the rate of turnover in vocabulary words, such that there is faster evolution in smaller populations (Jordan and Currie, in revision).

Jordan, F.M. & Currie, T.E (in prep.).
The effect of population size and density on rates of linguistic evolution.
Mace, R. & Jordan, F.M (2011).
Macro-evolutionary studies of cultural diversity: a review of empirical studies of cultural transmission and cultural adaptation. Phil. Trans. R. Soc. Lond. B. Vol 366:402-411.
Fortunato, L. & Jordan, F.M (2010).
Your place or mine? A phylogenetic comparative analysis of postmarital residence in Indo-European and Austronesian societies. Phil. Trans. R. Soc. Lond. B.
Jordan, F.M., Gray, R.D., Greenhill, S.J., and Mace, R (2009).
Matrilocal residence in ancestral in Austronesian societies. Proceedings of the Royal Society B: Biological sciences. Vol 276:1957-1964.