The phylogenetic roots of human lethal violence

Abstract

The psychological, sociological and evolutionary roots of conspecific violence in humans are still debated, despite attracting the attention of intellectuals for over two millennia1,2,3,4,5,6,7,8,9,10,11. Here we propose a conceptual approach towards understanding these roots based on the assumption that aggression in mammals, including humans, has a significant phylogenetic component. By compiling sources of mortality from a comprehensive sample of mammals, we assessed the percentage of deaths due to conspecifics and, using phylogenetic comparative tools, predicted this value for humans. The proportion of human deaths phylogenetically predicted to be caused by interpersonal violence stood at 2%. This value was similar to the one phylogenetically inferred for the evolutionary ancestor of primates and apes, indicating that a certain level of lethal violence arises owing to our position within the phylogeny of mammals. It was also similar to the percentage seen in prehistoric bands and tribes, indicating that we were as lethally violent then as common mammalian evolutionary history would predict. However, the level of lethal violence has changed through human history and can be associated with changes in the socio-political organization of human populations. Our study provides a detailed phylogenetic and historical context against which to compare levels of lethal violence observed throughout our history.

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Figure 1: Evolution of lethal aggression in non-human mammals.
Figure 2: Social behaviour and territoriality influence lethal aggression in mammals.
Figure 3: Lethal violence in humans.

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Acknowledgements

The authors thank E. W. Schupp, P. Jordano, M. Lineham, J. A. Carrión, M. Goberna, A. Montesinos, J. G. Martínez, C. Sánchez Prieto, R. Torices, R. Menéndez and F. Perfectti for comments on an early version of this manuscript.

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Contributions

The study was conceived by J.M.G. Data were compiled by all authors. Analysis was performed by M.V., J.M.G. and A.G.M. All authors discussed the results and contributed to the manuscript.

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Correspondence to José María Gómez.

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The authors declare no competing financial interests.

Additional information

The data used in this study are available in Supplementary Information section 9. Reprints and permissions information is available at www.nature.com/reprints.

Reviewer Information Nature thanks O. Bininda-Emonds, M. Pagel and M. L. Wilson for their contribution to the peer review of this work.

Extended data figures and tables

Extended Data Table 1 Outcome of the phylogenetic generalized linear model testing the effect of territoriality and social behaviour on the magnitude of lethal aggression in mammal species (n = 1,024 species)
Extended Data Table 2 Outcome of the t-tests assessing difference between the inferred value of lethal violence at each of the chosen ancestral nodes in the mammalian phylogeny and the phylogenetic estimates of human lethal violence
Extended Data Table 3 Outcome of the binomial tests assessing difference between the observed lethal violence in human societies and the inferred lethal violence according to the phylogenetic analysis

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Supplementary Information

This file contains Supplementary Text and Data, Supplementary Figures, Supplementary Tables and additional references (see Contents for details). (PDF 6950 kb)

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Gómez, J., Verdú, M., González-Megías, A. et al. The phylogenetic roots of human lethal violence. Nature 538, 233–237 (2016). https://doi.org/10.1038/nature19758

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