Humans have a terrible reputation for killing each another - and new research suggests that's not a surprise
According to new research from Spain's Higher Council for Scientific Research (CSIC), nearly one in five meerkats die at the hands (or paws) of their own. Contrary to their cute looks, meerkats and some other small animals murder each other more often than supposedly aggressive animals like wolves, brown bears, and humans.
In other words, the study found, people are pretty violent, but in the grand scheme of things we're actually just on par with our relatives.
"The biggest surprise was to realize how widespread is lethal violence among mammals," Dr José María Gómez, a professor of ecology at the University of Grenada who led the study, told Business Insider. "It was also striking that lethal violence was not concentrated in the groups that we tend to consider 'violent', such as carnivores."
Still, primates stand out for their violence compared with other animals.
The team found that primates - the group that contains humans, apes, monkeys, and lemurs - were particularly violent as a group, with the number of deaths being caused by a member of the same species at 2.3%. Apart from meerkats, the other four out of the top five spots belonged to primates - ranging from a whopping 16 to 19%.
The current statistic for humans killing each other is only slightly lower than the primate average at 2%, but this was higher in some prehistoric times, particularly during periods with many wars.
"Mammals, territorial and social species showed significantly higher values of lethal violence than solitary and non-territorial mammals," he said. "Sociability probably involves more opportunities to conflict than solitary habits."
In other words, being sociable provides more incentives and chances for killing each other.
Why do individuals in evolving societies still kill each other?
The team looked at many types of lethal violence including infanticide, cannibalism and deaths resulting from male-male fights. Each has a particular set of causes and circumstances, and Gómez explained that as long as conditions exist where some of these kinds of violence provides some benefits, deaths will continue to happen.
The study didn't explore why lethal violence occurs in societies that are supposedly evolving, but Gómez could speculate.
"Violence is sometimes an unintended result of some interactions between individuals. As long as conflicts exist, some lethal death is expected to occur eventually even if no one gets any profit out of it," he said. "We would say that lethal violence is a potential result of conflict solving... whether we can articulate ways to solve conflicts without lethal violence is an open question, but our study suggests that, to some extent, that can be done."
The team are now exploring whether different types of lethal violence, like infanticide, aggression or cannibalism, may have evolved from different patterns. This could help differentiate between why some methods are more common in some species. It could also start to help explain why animals can be so murderous when on the surface they appear to be cute and cooperative, such as meerkats.