A propensity to kill and maim members of our own species is largely programmed into human genes because we are primates, scientists claim.
Apes are generally more violent to one another than other mammals, and this tendency has been passed on to humans, a study suggests.
Levels of lethal violence between members of the same species have risen during 100 million years of mammalian evolution, according to the research.
By the time humans emerged it accounted for about 2 per cent of all the deaths of our early ancestors, compared with an overall rate across 1,024 living and extinct species of just 0.3 per cent.
While violent death is common, instances of members of a particular species killing each other are said to be much rarer.
Some animal families, such as whales, bats, and the lagomorph group that includes rabbits and hares, were far less inclined to murder than others, the study showed.
Primates, on the other hand, had a vicious streak hard-wired by evolution.
Human violence is mirrored in chimpanzees, our closest living relatives that share 98 per cent of human genes. In the wild, the apes organise “war parties” to hunt down and kill stray males from other chimpanzee groups.
The scientists, led by Dr Jose Maria Gomez from the Estacion Experimental de Zonas Aridas in Almeria, Spain, investigated more than four million deaths of both present day and extinct mammals using techniques derived from evolutionary biology.
In total, the research published in the journal Nature covered 1,024 species from 137 families dating back to the first mammals that lived some 100 million years ago.
An estimated two percent of all deaths of the earliest humans who appeared in the fossil record roughly 160,000 to 200,000 years ago were caused by personal violence, the findings showed.
This compared with 1.8 per cent for the common ancestor of all great apes.
Between 3,000 and 500 years ago the rate soared to a peak level of 15 per cent – 30 per cent – meaning nearly a third of all human deaths were due to homicide.
It then declined, and in modern societies that have police forces, legal systems and prisons, fewer than one in 10,000 deaths (0.01 per cent) were the result of human violence.
The research suggests the current low level of homicide death is only thanks to societal restraints that curb our natural instincts.