It turns out that humans are not as bad as they think to be. Hurting each other is not something that is genetic but most likely because of factors such as changes in social environment. A study published in Nature, led by José María Gómez of the University of Granada together with his colleagues, weighs in on how human's history of hurting each other came to be.

In order to find out the whys, the researchers decided to first look for comparisons of humans with other mammals. Do we just shed blood more than mammals? Do other mammals kill because of territory like humans? A painstakingly huge data of over four million deaths and usage of phylogenetic analysis are the basis of this new study.

For an effective comparison, researchers calculated the levels of violence in 1,024 mammal species from 137 taxonomic families and in about 600 human populations, ranging from about 50,000 years ago to the present. They zeroed in to deaths by war, homicide, manslaughter, infanticide, sacrifice, cannibalism and others. These cases, however, do not exactly tell if it involves a lone perpetrator or collective, or even coalitional.

Data from past 50,000 to 10,000 years agoare "statistically indistinguishable," but based on the archaeological finds, humans then were "hunters" and still lived ins mall groups that the researchers predicted that two percent of all human deaths are because of interpersonal violence, as compare to bats and whales, who hardly ever killed each of their kind. Results on different mammals vary, and that depends on each species' way of living. For example, animals that tend to live in groups are most likely violent such as wolves and chimps.

The study also revealed the most violent times in history of man happened during the Middle Ages, ranging from Genghis Khan to Crusaders, to Holy Roman Empire, until the Black Plague. There are many people who died during these events. Population density is another matter. For humans, density of a place does not equate to a riot. Mammals' lethal violence however can be triggered by this ecological drive.

The good news, humans can "outgrow"our evolutionary drive to kill but in order to achieve this, we must"modulate" the level of lethal violence by changing our social environment, Gomez said.