The Dark Side of Nature: Exploring Lethal Violence in Mammals
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Which mammal is most likely to be murdered by its own kind? It’s certainly not humans—not even close. Nor is it a top predator like the grey wolf or lion, although those at least are #11 and #9 in the league table of murdery mammals. No, according to a study led by José María Gómez from the University of Granada, the top spot goes to… the meerkat. These endearing black-masked creatures might be famous for their cooperative ways, but they kill each other at a rate that makes man’s inhumanity to man look meek. Almost one in five meerkats, mostly youngsters, lose their lives at the paws and jaws of their peers.
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Gómez’s study is the first thorough survey of violence in the mammal world, collating data on more than a thousand species. It clearly shows that we humans are not alone in our capacity to kill each other. Our closest relatives, the chimpanzees, have been known to wage brutal war, but even apparently peaceful creatures take each other’s lives. When ranked according to their rates of lethal violence, ground squirrels, wild horses, gazelle, and deer all feature in the top 50. So do long-tailed chinchillas, which kill each other more frequently than tigers and bears do.
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The point of this macabre census was to understand the origins of our own behavior. Gómez typically studies plants and insects, but he realized that the techniques he uses to studytheirevolution can be used to study our own. In particular, he noted that closely related species tend to show similar levels of lethal interpersonal violence. He could use those similarities to predict how violent any given mammalshouldbe, and whether it meets, exceeds, or defies those expectations. Humans do all three. Gómez’s team calculated that at the origin ofHomo sapiens, we were six times more lethally violent than the average mammal, but about as violent as expected for a primate. But time and social organizations have sated our ancestral bloodthirst, leaving us with modern rates of lethal violence that are well below the prehistoric baseline. We are an average member of an especially violent group of mammals, and we’ve managed to curb our ancestry.
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In the 17th century, he argued that modern society protects us from our brutish nature, lived in “continual fear, and danger of violent death. The primates—the order that includes us, apes, monkeys, and lemurs—seem to be especially violent. While just 0.3 percent of mammal deaths are caused by members of the same species, that rate rose to 2.3 percent in the common ancestor of primates, and dropped slightly to 1.8 percent in the ancestor of great apes. That’s the lethal legacy that humanity inherited.
That isn’t to imply determinism. Even within the apes, chimps are notably more aggressive than bonobos, which suggests that group-wide capacities for violence can be tempered by other factors. And history shows that humans have also varied greatly in our violent tendencies. We are influenced by our history, but not saddled to it.
