The researchers found around one in 50 deaths in the earliest human and Neanderthal bands 50,000 years ago were the result of foul play – roughly the same frequency as apes and monkeys.
These included deaths from cannibalism, executions, infanticide and war.
Fortunately for us, culture and modern civilisation mercifully means modern humans are no longer so prone to follow our instincts.
The level of inter-human killing is now on average around 1 in 10,000 worldwide.
Deadly violence used against members of one’s own species is common in the animal kingdom.
Killing rivals increases reproductive success – giving access to more mates and resources and granting higher status.
Scientists looked at around 1,024 different mammals, including mankind to assess the a ‘genetic’ level of violence.
Information on humans came from 600 human populations from 50,000 years ago to the present. It found 2 per cent of early humans died from ‘lethal interpersonal violence’.
If anything, the numbers may be an underestimate, as it is easier to tell whether someone has died from a bladed weapon, which could not be a natural cause, than from being hit by a blunt object.
The study overall found roughly 40 per cent of mammals were inclined to kill each other.
Some animals, such as bats and whales, were classed among the pacifists of the animal kingdom.
Meanwhile ‘seemingly peaceful animals’ such as hamsters and horses, surprisingly, can bump each other off.
But apes and monkeys – among which humans are also classed – were among the most bloodthirsty.
While this may sound high, in medieval times in Europe and in pre-conquest days in South America, violence levels were much higher.
The authors state that two factors increase the likelihood of a mammal killing its own species. One is sociability, the other is territoriality. Humans are both sociable and territorial, so this increases our likelihood of beating each other to death.
Dr Jose Gomez, of the Spanish National Research Council in Madrid, said: ‘We were – at the dawn of humankind – as violent as expected considering the common mammalian evolutionary history.’
The study published in Nature also showed levels of violence have changed throughout history – mostly in conjunction with social and political changes suggesting culture plays a key role.
Dr Gomez said: ‘This prehistoric level of lethal violence has not remained invariant but has changed as our history has progressed – mostly associated with changes in the socio-political organisation of human populations.
‘This suggests culture can modulate the phylogenetically (evolutionarily) inherited lethal violence in humans.’