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Murderous mammals’ evolution mapped

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Do dolphins duel to the death? Are hippos homicidal? And what about genocidal gerbils? Spanish researchers have mapped the extent of lethal violence across 1000 mammal species, from aardvarks to zebras. The scientists find that estimated rates of prehistoric human-on-human killings were six times higher than the average mammal, but similar to related primates, indicating a strong evolutionary link to lethal violence. Thankfully, the authors note, modern rates of such violence among humans are far lower, with socio-political organisation overriding our murderous tendencies.

Journal/conference: Nature

Organisation/s: Estación Experimental de Zonas Áridas, Spain

Media Release

From: Springer Nature

Human behaviour: The roots of human violence may lie in our evolutionary tree

Lethal interpersonal violence is a particular feature of primates and is likely to have been inherited by humans during the course of evolution, finds a new study published in Nature this week.

Violent behaviour directed towards members of the same species is known to be common in certain mammals, such as primates, but is virtually unknown in others, such as bats and whales; however it is not clear how much of human aggressive behaviour is driven by our position in the evolutionary tree. The psychological, sociological and evolutionary origins of human violence have long confounded academics, who have been unable to disentangle the relative importance of cultural and non-cultural components.

José María Gómez and colleagues compile data from over 4 million deaths and quantify the level of lethal violence in 1,024 mammal species from 137 taxonomic families and in about 600 human populations, ranging from about 50,000 years ago to the present. Taking data from a variety of human and mammalian sources, they use phylogenetic comparative tools to predict that the overall proportion of human deaths caused by interpersonal violence stands at around 2% — a figure that matches the observed value for prehistoric man.

The authors also investigate how the evolutionarily inferred level of lethal violence differs from that empirically observed during human history. They show that levels of lethal interpersonal violence have changed throughout history, mostly in conjunction with changes in socio-political organization of human populations. These results suggest that culture can influence evolutionarily inherited lethal violence in humans.

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