Humans have evolved from a particularly violent branch of the animal family tree, according to a new study which found that we have been this way pretty much since the dawn of humankind. The mammalian order of primates - to which humans belong - kill within their own species nearly six times more often than the average mammal does, researchers led by Jose Maria Gemez from Spain's Higher Council for Scientific Research (CSIC) said. Whales rarely kill each other; the same goes for bats and rabbits. Some species of felines and canines occasionally kill others within their own species - for example, when sparring over territory or mates. Yet most primates use lethal violence with greater frequency than the other animal groups, sometimes even killing their fellow species members in organised raids. Humans exhibit a level of lethal aggression that fits this pattern in primates, the researchers said. Humans are equally as violent to each other as most other primates are, and we have been this way pretty much since the dawn of humankind, 'Live Science' reported. However, that does not mean we cannot change our ways, the research suggests. Researchers analysed data from over 4 million deaths among the members of 1,024 mammal species from 137 taxonomic families, including about 600 human populations, ranging from about 50,000 years ago to the present. They calculated that about two per cent of all human deaths have been caused by interpersonal violence - a figure that matches the observed values for prehistoric humans such as Neanderthals, and most other primates. The study was published in the journal Nature.