Although it’s unclear whether genetics or other factors are responsible, new study suggests that lethal violence is part of our evolutionary history 
 
 Humans are predisposed to murder each other, new research suggests, although it remains unclear if it’s down to genetics or other factors. “At least to some extent, the way humans organise in societies influences our levels of lethal violence.” 
 
 The question of human violence has puzzled thinkers for centuries, from Thomas Hobbes in the 17th century, to contemporary psychologists such as Jared Diamond and Steven Pinker, the Johnstone professor of psychology at Harvard University and author of The Better Angels of Our Nature. Pinker has previously argued that humans engage in lethal violence as a “natural condition,” but that deaths from such violence have decreased with the rise of modern societies with sophisticated institutions and laws. Scientists calculated the rate at which more than 1,000 mammal species kill their own kind, and noticed how closely related species have similar rates of lethal violence. Around 1.8% of deaths are thought to have been down to lethal violence for the ancestor of the great apes, and around 2% for the first humans - a figure more than six times higher than at the origin of mammals.
– Violence comes naturally to humans, but we are far less murderous than we used to be, a new study shows. Scientists in Spain who examined the tendency among more than 1,000 mammal species to kill their own found that humans have been "particularly violent" throughout our history, reports the AP. Early humans killed each other at a rate of about 20 in 1,000, but got more violent during the Middle Ages when the rate shot up to 120 in 1,000. After studying 600 human populations from the Stone Age to the present day, the researchers concluded that "lethal violence is part of our evolutionary history but not carved in stone in ‘our genes,’” lead author Jose Maria Gomez tells the Guardian. Levels of violence are influenced by societal pressures and have "decreased significantly in the contemporary age," says Gomez. Still, the study published in the journal Nature found modern humans to be pretty dangerous, killing each other at a rate of about 13 in 1,000. At least we're not the worst. That title goes to, surprise, the meerkat. "Almost one in five meerkats, mostly youngsters, lose their lives at the paws and jaws of their peers," Ed Yong writes in the Atlantic. The meerkats were followed by two types of monkeys and assorted lemurs. The New Zealand sea lion, long-tailed marmot, lion, branded mongoose, and grey wolf round out the top 11. Not surprisingly, violence was more common among mammals who share territory than among loners like bats and whales. "Our study suggests that the level of lethal violence is reversible and can increase or decrease as a consequence of some ecological, social, or cultural factors," says Gomez. (A study found early humans may have killed off real-life hobbits.)