What would you say is the deadliest animal on earth–the most dangerous, brutal, destructive? The wolf? The tiger? The great white shark?
Nope. The best answer is the species known as Homo sapiens–human beings. Not only do we kill members of other species at a rate unparalleled in the history of the planet, but we do something which is singular in the animal world: we make a point of killing each other, too.
That is, this kind of behavior was thought to be singular until just a few decades ago. It was 1974 when the first hard evidence of intra-species murder was documented in animals other than man–that is, animals going out of their way to find a member of their own species and kill it without immediate provocation. The species witnessed committing these murders was the chimpanzee, a close relative to human beings.
Further observation of primate behavior has discovered that not only is intra-species murder common, so are such brutalities as rape, battering of females, and infanticide. It seems that the worst traits in human behavior started developing long before human beings per se existed; as primates we have a very nasty evolutionary inheritance.
Does this mean that war, crime, and violence among humans is unavoidable?
It would not be fair to go that far; but the evidence of violence in those species most closely linked to our own does suggest that humanity will have to work very hard at overcoming its genetic inheritance if we are going to live in peace–or continue to live.