Humans are Natural Predators

According to a new study, genetics and evolution have made an impact on the murderous behavior of the human species. However, becoming civilized has tamed some of these instincts.

Scientists have looked at the homicide rate of more than 1,000 species that kill their own, and noticed that there are similar rates of lethal acts. Essentially, this means that the evolution of these species can tell us a lot about how violent the species is.

This study, which was published in Nature, says that humans lie in the middle of a quite violent group of mammals that have all evolved together…and these mammals have a very violent and murderous past. What does this mean for us? It means that humans have likely inherited violent tendencies from our ancestors.

Let's look at the numbers. When looked at as a group, the rate of all mammals murdering their own is about three in 1,000. However, when we look at our ancestors, and many primates, for that matter, this number is closer to about 20 in 1,000. In certain periods of time, this number even rose to about 120 in 1,000, such as during the medieval era, which ran from around 700 to 1500 A.D. Fortunately, we have seen these numbers fall, and when you take humans, alone, the current rate is about 13 in 1,000. So, we are now much less violent than we were just 1,000 years ago.

It's true that we, as humans, are killing each other less than we used to, but we are still not as peaceful as some of our mammalian cousins. For example, killer whales, which are one animal that has a high level of intelligence, has a rate of violence against its own of around zero. In fact, most whale species are quite peaceful to their own kind.

So, we are more violent than whales, but when compared to mammals such as baboons, cougars, and lemurs, we are far less violent, as these animals have murder rates closer to 100 per 1,000.

Since this study examined violence in a way that compared closely related species, it's not a surprise that these species had similar levels when looking at violence. Furthermore, the more closely related a species is to another, the more similar their levels of violence.

It is difficult to calculate rates for lethal violence for our ancestors, but we can get a rough idea based on looking at archaeological findings. What was found after looking at thousands of these sites is that things such as culture and government lower the rates of lethal violence. This also suggests that the level of murder among species is reversible, and that it might increase or decrease based on social, ecological, or cultural factors. These findings are similar to a previous study from Harvard that looked at the history of violent crimes, such as rape, as well as war, murder, and bigotry.

When we look at all of these facts, humans are social, territorial, and naturally violent. But, as modern society has become developed and we have engaged in more civilized activities, the rates of violence have fallen. What's really interesting is that this study shows that most mammals are not murderous towards their own kind, but others, such as wolves, lions, and primates, including humans, actually do engage in this behavior. What it could come down to is that mammals that are murderous towards their own kind are both territorial and social.