he Taymouth Hours © British Library, MS Yates-Thompson 13, Fol 28

Are Humans as Lethal today as in the Middle Ages?

The chance of dying from violence in the Middle Age was at least five times higher than it is today. It appears culture and state-formation has an important peacekeeping role to play.

These days NATO Troops are being posted in Eastern Europe to stave off Russian aggression. Meanwhile the Chinese are threatening USA with grave consequences if the status of Taiwan is questioned and the build-up of artificial islands in the South China Sea is hindered. It seems, all-out-war is once more threatening in the horizon. One should have thought that the horrors of the 20th century would stop even the most foolish and self-engrossed dictator, but apparently this is not the case.

The question is: do we not get wiser?

This question has of course been voiced for as long as historians, philosophers and social scientists have studied the psychological, sociological and historical roots of violence. However, recently, a Spanish group of scientist had a letter posted in Nature, which asked the question in a somewhat different manner: they asked to the phylogenetic – that is long-term evolutionary – roots and levels of human lethal violence? And to what extent shifts in these levels of violence compared to the inherant violence.

Lethal Violence among Mammals

A Massacre of Family Members @ The J. Paul Getty Museum
A Massacre of Family Members @ The J. Paul Getty Museum

From an evolutionary point of view lethal violence is seen as an adaptive strategy favouring the perpetrator’s reproductive success in terms of mates, status and resources; this, of course, implies that as evolution proceeds, we should tend to get more violent than our forbears. However, specific ecological and cultural contexts may further or hamper these traits, creating milieus where violence does not pay off. As an example may be mentioned high incarceration levels for young males in a society, which might seriously impede their possibilities to procreate. As the authors write: “disentangling the relative importance of cultural and non-cultural components of human violence is challenging, owing to the complex interactions between ecological, social, behavioural and genetic factors” (p. 233)

But violence is not specific to humans; it is also prevalent among primates, who exhibit high levels of intergroup aggression and infanticide. In fact, there is a level of aggression, which can be detected among mammals in general.

I order to study the complex problem in detail, the scientist set out to quantify the level of lethal violence in 1,024 mamalian species from 137 different families as well as in 600 human populations, ranging from the Palaeolithic era to the present. The level of letal violence was defined as the probability of dying from intraspecific violence compared to all other causes.

Lethal violence was found among 40% of the studied mammal species, but the authors consider this an underestimation. More interestingly, though, was the conclusion that the level of lethal violence was higher in social and territorial species than in solitary and non-territorial species. Discounting this difference, the level of violence was 2.0 +/-0.02% of all deaths. When territoriality and sociability was entered into equation, the level was measured to 2.1 +/-0.02%.

Next phase was to study humans as well as their forebears (homineuds, primates etc). This led to a conclusion that the level of lethal violence during human prehistory did not differ from the phylogenetic predictions. However, compared to humans living under specific circumstances (old world/new world/ancient, Middle Ages and modern period), this shifted.

The Middle Ages

What it showed is that the chances of dying from lethal violence in the iron and Middle Ages were no longer hovering around 2% but significantly higher, namely 7.7 – 8.1 %. However, moving into the modern age, the chances of dying from violence fell significantly below the level, which might be expected from an evolutionary point of view. In the contemporary times, this is even more reduced!

Another interesting consequence is that prediction would be that levels of lethal violence would inflate when density of population grew; but the opposite is in fact the case. “High population density is therefore probably a consequence of successful pacification, rather than a cause of strife”, writes the authors.

Another fascinating conclusion is that the levels of lethal violence was also explored inside specific types of social formation – bands, tribes, chiefdoms, and states. This led to a conclusion that life in societies governed by chiefs, were nearly 6% more violent than should be expected. Life in states, characterised by monopolized violence (armies and police) would on the other hand be less violent than evolution should otherwise indicate; specifically this is the case for developed modern states.

This means that people in the Middle Ages were seven to eight times more likely to die from lethal violence as are their descendants – us – living in modern times. It also appears that one reason for our more civilised behaviour is that we live in societies governed by heads of states and not as members of clans governed by chiefs.


The scientists conclude that the prehistoric levels of violence were, as might expected from their phylogenetic analyses, “at the dawn of humankind as violent as might be expected considering the common mammalian evolutionary history.”Later, however, this prehistoric level has shifted considerably according to what socio-political type of organisation, people lived under. “This suggests that culture can modulate the phylogenetically inherited lethal violence in humans”, they conclude.

Naturally, the study has been queried; especially has questions been raised concerning the historical material, which is probably skewed. Did dead warriors and solders for instance get transported back to be buried in their local cemetery? Or were they left on the battlefield to be scavenged by predators? Would people eventually have died of violence if they had not been subjected to plagues? However, as a first report on the statistical relations between the inherent level of violence and that of specific historical periods and circumstances, this is very interesting.

It also seems as: yes, indeed we do get wiser…


By José María Gómez, Miguel Verdú, Adela González-Megías and Marcos Méndez
In: Nature: Letter. (2016) Vol 538,  pp. 233–237


In: Science. Sept. 2016