Humans may have evolved aggression, but that doesn’t mean we were hard-wired for war

Archaeological studies suggest changes in society some 10,000 years ago likely caused our capacity for conflict, rather than genetic evolution.

Are humans innately warlike? It is not difficult to find arguments saying that we are. In the book The Dark Side of Man, anthropologist and ecologist, Michael Ghiglieri insists that war predates humanity, that it is natural, and that it vies with sex for the distinction of being the most significant driver of human evolution.

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In his recent book, Why We Fight, Mike Martin, also argues that war is caused by subconscious desires formed over millennia by evolution. This view has a long pedigree. Thomas Henry Huxley wrote in 1888 that the struggle of all against all was the normal and natural condition of existence.

Austrian zoologist Konrad Lorenz, whose work on animal aggression helped establish the field of ethology and earn him the Nobel Prize in Physiology in 1973, argued through the savage process of their evolution, human had acquired an instinct for aggression that had served them well. ‘There cannot be the slightest doubt’, Lorenz insisted, ‘that human militant enthusiasm evolved out of a communal defence response of our pre-human ancestors’.

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In the 1970s, primatologist Jane Goodall stunned the world when she wrote up her observations of warring and genocidal chimpanzees in Gombe, Tanzania. If our closest relatives, the chimpanzees, engaged in warfare and coalitional killing, then it would seem fair to suggest that aggressiveness and a tendency to form coalitions of males to attack and kill outsiders were inherited traits.

A related theory suggests an innate inclination to war stems not from conspecific conflict – a conflict between animals belonging to the same species – but from inter-specific struggles with prey and predators. But the earliest humans were not just hunters. They were also the hunted.

In her book Blood Rites, American author and political activist Barbara Ehrenreich writes that from this deeply repressed human experience, we developed the ‘fight or flight’ instinct and our capacity to band together to see off common enemies. These psychological building blocks for war were honed through thousands of years of evolutionary experience in coping with predators until they became an ‘inborn tendency’.

With very few exceptions, there is almost no archaeological evidence of warfare prior to about 9,000 BCE

But how well does this image of humans as natural-born warriors fit the archaeological evidence? Not very. Although there was individual-level violence, there is remarkably little evidence of the type of group-level violence we today call war prior to the emergence of the first organised political entities.

The absence of proof about war’s existence in the earliest of human times does not by itself provide proof of its absence. That said, violence and war do leave discernible traces in archaeology in the form of damaged bones, weapons, and fortifications. And what is striking is that with very few exceptions, there is almost no archaeological evidence of warfare prior to about 9,000 BCE. Evidence of war remains very rare until the emergence of organised early civilisations in the Middle East around 7,500 BCE.

A survey of the fossil record up to 10,000 BCE reveals only a relatively small number of deaths caused by conspecifics, most of which are attributable to cannibalism and individual-level violence. Clear evidence of deaths from weaponry such as spears and arrows emerges only after 10,000 BCE.

There is likewise little evidence of fortified settlements, a clear sign that communities feared violent raids, before around 7,000 BCE, after which they became quite common, especially in Europe and the Middle East. From this point in history, the fossil record contains several examples of humans killed by others with weapons.

This stands in contrast with the ample evidence of violent deaths after the transition towards more sedentary societies in Europe during the Mesolithic (10,000–5,000 BCE) and of armed conflict from the Neolithic period of the first farmers after 5,000 BCE. What is missing, though, is evidence of warfare before that time that would be necessary support the notion that humans were warfighters from the start.

The same story can be read in cave paintings. Paintings dated before around 10,000 BCE reveal little evidence of conspecific violence, warfare, or weaponry. The total record of rock art for this period numbers in the several thousand. The vast majority portray animals, either living in peace or being hunted. Only around 130 paintings may include humans, some which may not actually be human since the drawings are too crude and not sufficiently well preserved to determine this precisely, and most are portrayed in peaceful scenes.

Of all the paintings of this era, only 4 depict people injured by arrows and of these 2 may well be animals (it is unclear whether one of the appendages on the creature depicted is a limb or a tail).

The picture changes, literally, after about 8,000 BCE. From that time, depictions of conspecific violence, weapons, and battle scenes proliferated. There is therefore a clear contrast: depictions of warlike fighting are all but absent from rock art until the dawn of the Mesolithic age, but become more common thereafter. Even in the Mesolithic, however, depictions of war remained a minority.

A brutal massacre occurred in Nataruk, Kenya around 8,000 BCE

There are two important exceptions to this picture. But the fact that they are exceptions helps prove the general rule. At Jebel Sahaba in Sudanese Nubia, close to the Nile, 59 skeletons dated 10,000–12,000 BCE were discovered. Of these, including the skeletons of men, women, and children, 24 showed signs of having suffered violent deaths, with stone projectiles intimately associated with or embedded within them. Several of the adult males had multiple injuries, whilst markings on the children suggested that they had been executed.

The findings at Jebel Sahaba are usually taken as the first definitive archaeological evidence of war, though questions remain about whether the victims were indeed killed in battles (as opposed to executions, rituals, etc.) and whether they died at the same time. But even if we set aside these questions, we still have the problem of the site’s exceptional character.

Fred Wendorf, who led the team that excavated Jebel Sahaba, suspected it was a special burial area and observed that a cemetery excavated just across the Nile, and dating from the same period, revealed no evidence of violence amongst its 39 skeletons. To this day, Jebel Sahaba stands alone in providing evidence of mass violence before 10,000 BCE.

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The same may be said of the famous walls of Jericho, which date from 8,300–7,300 BCE. Among settlements of its time, Jericho was alone in erecting fortifications, suggesting that other societies did not share its fear of endemic violence. Indeed, there are no archaeological signs of warfare anywhere else in the Middle East dating within a thousand years of the early Jericho walls.

Another fortified site, at Catal Huyuk (in modern Turkey), dates from 7,100–6,300 BCE, well within the time of transition in which war became more common.

Whether it be fossils, weapons, art, or fortifications, the archaeological record is surprisingly clear: warfare was not ubiquitous to the earliest humans but emerged as societies changed and evolved after around 8,000 BCE, though obviously these transitions occurred in different ways, at different times, in different places. Key to the emergence of war around 8,000 BCE were the profound social, economic, and environmental changes of the time.

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All this suggests that war coevolved with society. Humans certainly have a genetic capacity for aggression and violence, but this does not equate to an innate disposition towards war any more than our genetic capacity for empathy equates to an innate disposition towards peace. It would seem that it is society, not biology that condemns humanity to war.

World Peace (And How We Can Achieve It)by Alex J. Bellamy is available now (£20, OUP)

World Peace (And How We Can Achieve It) by Alex J. Bellamy is available now (£20, OUP)