Philosophical Transactions of the Royal Society B: Biological Sciences
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Is horizontal transmission really a problem for phylogenetic comparative methods? A simulation study using continuous cultural traits

Thomas E. Currie

Thomas E. Currie

Human Evolutionary Ecology Group, Department of Anthropology, University College London, London WC1H 0BW, UK

Hasegawa Laboratory, Evolutionary Cognitive Science Research Center 1F, Building 17, Department of Cognitive and Behavioral Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan

[email protected]

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,
Simon J. Greenhill

Simon J. Greenhill

Department of Psychology, University of Auckland, Auckland 1142, New Zealand

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and
Ruth Mace

Ruth Mace

Human Evolutionary Ecology Group, Department of Anthropology, University College London, London WC1H 0BW, UK

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Published:https://doi.org/10.1098/rstb.2010.0014

    Phylogenetic comparative methods (PCMs) provide a potentially powerful toolkit for testing hypotheses about cultural evolution. Here, we build on previous simulation work to assess the effect horizontal transmission between cultures has on the ability of both phylogenetic and non-phylogenetic methods to make inferences about trait evolution. We found that the mode of horizontal transmission of traits has important consequences for both methods. Where traits were horizontally transmitted separately, PCMs accurately reported when trait evolution was not correlated even at the highest levels of horizontal transmission. By contrast, linear regression analyses often incorrectly concluded that traits were correlated. Where simulated trait evolution was not correlated and traits were horizontally transmitted as a pair, both methods inferred increased levels of positive correlation with increasing horizontal transmission. Where simulated trait evolution was correlated, increasing rates of separate horizontal transmission led to decreasing levels of inferred correlation for both methods, but increasing rates of paired horizontal transmission did not. Furthermore, the PCM was also able to make accurate inferences about the ancestral state of traits. These results suggest that under certain conditions, PCMs can be robust to the effects of horizontal transmission. We discuss ways that future work can investigate the mode and tempo of horizontal transmission of cultural traits.

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