Injuries are part of everyday life, from a scratch on the skin to a broken bone to a fatal trauma. Although many injuries are accidental, others can arise as a consequence of an individual’s or a group’s behaviour, activity or social norms — characteristics that tell us about societies and the inherent tensions and risks within and between different groups. Writing in Nature, Beier et al.1 provide evidence that challenges the long-standing view2 that Neanderthal populations experienced a level of traumatic injuries that was significantly higher than that of humans. The result calls into question claims2,3 that the behaviour and technologies of Neanderthals exposed them to particularly high levels of risk and danger.
Reports of injuries and deaths are constantly in the news. As well as being drawn to read the stories of individuals, such information is of interest because of what it tells us about our societies. However, to fully understand what might determine the current degree of violence and injuries, we also need to look back at the past and identify the causal underpinnings. But how far back should we look? Arguably, right back to the evolutionary origins of processes that shape behavioural, social and cognitive tendencies and abilities.
Anthropologists study skeletal remains to reconstruct aspects of ancient lives, building an ‘osteobiography’ that casts light on part of the life history of an individual. Skeletons preserve — in the form of holes, misshapen surfaces, bone misalignments and secondary fractures radiating out from a point of impact — a signature of the traumas that resulted in fractured, cut or perforated bones, even if the injuries subsequently healed4,5.
Traumatic lesions have been frequently identified in Neanderthal fossils, particularly in the head (Fig. 1) and neck, leading to the view2 that higher levels of skeletal injury occurred in Neanderthal populations than in human populations. However, this is not so, say Beier and colleagues. The authors assessed published descriptions of Neanderthal and modern human fossil skulls found in Eurasia from approximately 80,000 to 20,000 years ago. Comparing the number of injured and non-injured Neanderthal and human skulls, the authors report similar levels of head trauma in both groups.
The power of Beier and colleagues’ analyses lies in their study design. Instead of comparing Neanderthal data with those of more-recent or living human populations, as previous studies have done2,6, the authors based their comparisons on humans who not only shared aspects of their environment with Neanderthals, but whose fossil record also has a similar level of preservation. Beier et al. analysed data for 114 Neanderthal skulls and 90 human skulls. They gathered the data for 14 skull bones, and obtained information that ranged from 1 bone in poorly preserved fossils to data for all 14 bones per individual for well-preserved ones. In total, the authors recorded trauma incidence in 295 Neanderthal bones and 541 human bones. They also collected other information, such as the percentage of each of the 14 bones that was preserved for each individual, as well as details including sex, age at death and the fossil’s geographic location.
Beier et al. ran two sets of statistical analyses — one based on the presence or absence of trauma in each of the skull bones, the other on individual fossil skulls as a whole — to test whether there were any statistically significant differences between the prevalence of trauma in the Neanderthal and human fossils. The authors also assessed whether trauma prevalence was linked to sex or age, taking into account fossil preservation, geographic location and possible interaction effects between the different variables. The two analyses gave similar results.
The more complete the fossils are, the more likely they are to have preserved evidence of injuries. This might seem obvious, but is an issue often ignored in such studies. Beier et al. offer a way to deal with this type of bias in the available material. Once the authors take into account the extent of fossil preservation, the predicted prevalence of trauma in Neanderthals and humans is almost the same.
Both Neanderthal and human males had a much greater incidence of trauma than did the females of their respective species. This pattern remains the same for humans today7. One final intriguing result is that, although traumatic injuries were present across all of the age ranges studied, Neanderthals that had trauma to the head were more likely to have died under the age of 30 than the humans were. The authors interpret this result as evidence that, compared with humans, Neanderthals either had more injuries when they were young or were more likely to have died after being injured.
Beier and colleagues’ study does not invalidate previous estimates of trauma among Neanderthals. Instead, it provides a new framework for interpreting these data by showing that the level of Neanderthal trauma was not uniquely high relative to that of early humans in Eurasia. This implies that Neanderthal trauma does not require its own special explanations, and that risk and danger were as much a part of the life of Neanderthals as they were of our own evolutionary past. The result adds to growing evidence that Neanderthals had much in common with early human groups. However, the finding that Neanderthals might have experienced trauma at a younger age than humans, or that they had a greater risk of death after injury, is fascinating, and might be a key insight into why our species had such a demographic advantage over Neanderthals.
Is this the final word on the subject of Neanderthal trauma? The answer is no. Beier and colleagues assessed only skull trauma. What if Neanderthals accumulated more injuries to their bodies than did humans? There are data suggesting that this might be the case8. Furthermore, although the authors’ analyses demonstrate the power of a well-designed study based on large samples, the data they used were recorded by many researchers and at varying levels of detail, raising the possibility of methodological biases.
Lastly, the causes of the injuries could provide some elusive insights into behaviour, activities or social norms in the past. From the shape, location and extent of traumatic injuries in skeletons, and characteristics such as the sharpness of fracture edges or the degree to which injuries had healed, it is sometimes possible to establish the most likely cause of a trauma — for example, whether the injury probably arose as a consequence of a hunting accident3, interpersonal violence10 or inter-group conflict11. Moreover, surviving severe trauma might indicate that the injured person was cared for by members of their society12. Establishing the likelihood of each of these scenarios among Neanderthals and early modern humans will no doubt continue to challenge scientists for many years to come.
Nature 563, 634-636 (2018)