The rate of lethal violence is 7 times higher than the average for all mammals.
A new study of 1,024 mammal species has determined which animals are the most vicious killers of their own kind. Killer whales perhaps? Pit bulls maybe? For the answer, just look in the mirror.
“Step back and view our species objectively from the outside, the way a zoologist would carefully observe any other animal, or see us the way every other creature perceives human beings. The brutal reality could not be more evident or more horrifying. We are the most relentless yet oblivious killers on Earth.
“Our violence operates far outside the bounds of any other species. Human beings kill anything. Slaughter is a defining behavior of our species. We kill all other creatures, and we kill our own. Read today’s paper. Read yesterday’s, or read tomorrow’s. The enormous industry of print and broadcast journalism serves predominantly to document our killing. Violence exists in the animal world, of course, but on a far different scale.
Carnivores kill for food; we kill our family members, our children, our parents, our spouses, our brothers and sisters, our cousins and in-laws. We kill strangers. We kill people who are different from us, in appearance, beliefs, race, and social status. We kill ourselves in suicide. We kill for advantage and for revenge, we kill for entertainment: the Roman Coliseum, drive-by shootings, bullfights, hunting and fishing, animal roadkill in an instantaneous reflex for sport. We kill friends, rivals, coworkers, and classmates.
Children kill children, in school and on the playground. Grandparents, parents, fathers, mothers–all kill and all of them are the targets of killing…” — R. Douglas Fields, Why We Snap, p. 286, 2016.
After writing those words in my new book Why We Snap, I have been frequently challenged for being overly harsh on the species that has chosen to christen itself “sapiens,” (the wise one). But I was not offering social commentary. I was providing an objective, zoological description of this species.
This week, Maria Gomez and colleagues, zoologists working in Spain, published the results of their in-depth research in a report in the journal Nature on the evolutionary roots of the human propensity to kill their own kind. The researchers compiled data on lethal violence within 1,024 species of mammals, and the results verify my description of us. The analysis shows that deaths caused by other members of the same species is responsible for 0.3 percent of all deaths on average for all mammals, but the rate of lethal violence among Homo sapiens is 7 times higher. Together with our primate ancestors, we stand out as aberrations in our penchant to kill our own kind.
The reasons can be traced back to our primate ancestors, which are exceptionally violent creatures, killing each other at a rate of 2.3 percent like we do. These data indicate that the incessant repetition throughout recorded history and in prehistoric times of murder and war among all cultures of human beings has its roots in our evolutionary stalk.
In part, the reasons for this rampant self-killing appear to relate to our big brains and the conscious awareness and conniving that big brainpower makes possible, but primarily because of two other key aspects of Homo sapiens and other primates: fierce territoriality and living in social groups.
Across all mammalian species, conspecific deadly violence is highly correlated with these two factors. A double hit of both factors compounds the violence. Whales and bats are highly social, but not territorial, for example, and they have very low rates of killing their own kind. Human beings are highly social but extremely territorial — “Trespassers will be shot!” “He cut into my lane!”
When researchers examined how different types of social groups of humans affect the rate of killing, they found that lethal violence was common in present-day societies organized into bands or tribes, and severe violence is frequent in chiefdoms because of territorial disputes, population and resource pressures, and competition for political reasons, but violence decreased in state-run societies.