Murders are in the news so frequently that you may quietly wonder: are people just naturally violent? We can answer that question by looking at the rest of the animal kingdom. Are we Homo sapiens any more murderous than, say, monkeys, mice, or meerkats? [Music] A team of researchers in Spain found out by gathering data for more than one thousand mammal species, and they found that killing is actually pretty rare. Okay sure, predators will eat prey, but less than half of the studied species kill members of their own kind. And we humans are nowhere near the top of the chart of the most murderous mammals. We’re not even in the top 30. Some of those top species include obvious ones: predators like lions, bears, and wolves. But the list has surprises too. Cute things like ground squirrels, wild horses, deer. The adorable long-tailed chinchilla is sitting at number 14. And at the number 1 most murderous mammal? The meerkat. They might seem lovable, but around 20 percent of meerkats lose their lives to other meerkats. Primates, the group we belong to, turn out to be an unusually violent bunch. They are 8 times more likely to kill each other than other mammals are. This makes sense: Primates are both territorial and social, two factors that provide the motive and opportunity for murder. So we descend from a group of unusually murderous mammals. But what’s happened since then? To find out, the Spanish team combed through archeological data and historical records. They found that in paleolithic times, lethal violence caused 3.5% of all human deaths, making our ancestors only slightly more violent than the average primate. But as our societies got bigger, our rates of lethal violence increased, rising to around 12% during the Medieval period. But, once we formed large states and became more organized, institutions and the rule of law reduced rates of murder, which are now much lower than in our prehistoric past. The philosopher Thomas Hobbes would have approved. In the 17th century, he argued that modern society protects us from our brutish nature. Not so, said Jean-Jacques Rousseau, another philosopher who believed that humans are naturally good, and civilization is what corrupts us. So did Hobbes win this age old debate? Well maybe, but there’s a catch. Some researchers argue that how a mammal species kills its own kind matters more than the rate at which it does the killing. And for primates, the most common MO is infanticide. They kill their babies. But what makes humans so different is that we kill each other as adults at an exceptionally high rate. It is adult homicide that makes us part of a very small club of violent mammals that includes the like of wolves, lions, and spotted hyenas. Human violence may be rooted in our evolutionary past, and we may tamed our lethal proclivities, but like it or not, when it comes to violence, humans are still exceptional. This is You Are Here, a new series from the Atlantic about the science behind everyday life. Let us know what topics you want us to explore in the comments. I’m Ed Yong, thanks for watching.