The prehistory of compassion.

B eyond the biological traits that differentiate ancient species of hominins from extant humans, differences in social organization remain an important yet difficult issue to assess. Psychological features and interindividual relations, in particular, are among the least accessible aspects of past behaviors. Although the fossil and archaeological records do not easily allow us to tackle these kinds of issues, contrasting views on the cognitive capabilities and behavioral sophistication of fossil human species have often been expressed. In this issue of PNAS, Gracia et al. (1) provide new evidence on the survival of an abnormal individual with possible cognitive deficits from a group of pre-Neandertal Pleistocene hunter-gatherers, currently assigned to a geological age of 500 ka. The cranium SH14 from the Sima de los Huesos (Sierra de Atapuerca, Spain) is the earliest documented case of human neurocranial and brain deformity in the fossil record to date. Despite her/his pathological condition, this individual was not rejected at birth and survived until at least 5 years of age, apparently receiving the same attention as other children from the group. Particularly extreme pathologies, allegedly necessitating some support by conspecifics to allow the survival of their bearer, have provided the ground for debates on the level of altruism and compassion reached by ancient hominins. Often underlying these debates is the notion that, in this respect, their behavior was similar to our own and different from that of apes. Among the Pleistocene hominins, attention has been focused on the Neandertals in particular. This group has provided an abundance of paleontological material mostly dating between ca. 200 ka and 30 ka, including nearly complete skeletons. Each of these rather complete skeletons displays one or more detectable traumatisms on the bones, which, in a few cases, resulted in significant impairments. One of the best known examples is that of a male individual from the site of Shanidar (Iraq) who survived an unrepaired fracture of the right arm above the elbow (2). Subsequently, his upper arm became atrophied and nonfunctional, and he may have lost his right hand and forearm entirely. In addition, this individual was likely partially blind and deaf, and had difficulties with locomotion. As the Shanidar 1 man apparently survived until an advanced age for a Neandertal (ca. 40 years), it has been argued that his survival was possible only because he received support from other adults in the group. Similar claims for the social support of impaired individuals have been made, in particular, about edentulous adults who might have needed help with feeding from their companions. Significant antemortem tooth loss and alveolar bone loss are well-documented in Neandertals but less common and more limited in older periods of the Middle (0.78–0.13 my ago) and Lower (1.7–0.78 my ago) Pleistocene. In the Late Middle Pleistocene, all of the teeth from a portion of human mandible from Bau de l’Aubesier (France) were lost ante mortem or mechanically unstable at the time of death, with extensive bone loss and the development of abscesses along the dental arcade (3). Although this individual was still able to chew, his ability to masticate tough or hard food items would have been difficult and painful. A much older and even more complete edentulous specimen was yielded by the site of Dmanisi (Georgia), where the skull (D3444) and associated mandible (D3900) of an early form of Homo erectus, dated ca. 1.77 my ago, represent the earliest and best-preserved case of severe masticatory impairment in the hominin fossil record (4). Over its lifetime, this individual had lost all of its teeth except one, and thus, must have survived for a significant period by consuming only soft plant and animal foods that were easy to chew. The question is whether some external help was absolutely required for such an individual to have access to this peculiar diet (5). As underlined by DeGusta (5), this kind of assessment can only be conducted in a comparative way. In fact, tooth loss surpassing that of Bau de l’Aubesier 11 and even approaching that of D3444/D3900 has been documented in apes (5, 6). Primatologists studying chimpanzees in the wild have also reported several cases of serious impairments. Individuals with snare injuries resulting in severe upper limb wounds or even complete amputations of one hand have been observed (7), demonstrating that these disabilities can be overcome by young or adult apes without much conspecific care. However, these severe pathologies reported in non-human primates result primarily from wounds inflicted over a lifespan or from the senescence of adults already wellintegrated into their groups. What seems to be lacking in the ape repertoire is the survival of individuals with serious congenital abnormalities. In this respect, SH14 is quite interesting, even if she/he did not survive into adulthood. The impact of this individual’s cranial malformation on her/his capabilities is difficult to assess, because, today, cognitive impairment occurs relatively infrequently in cases of craniosynostosis with only one affected cranial suture (8, 9). However, she/he certainly displayed abnormal anatomical features already visible in her/his first year of life. A similar case is represented by the Middle Pleistocene hominin from Salé (Morocco) (10). The Salé individual was likely a female who reached adulthood even though she suffered cranial distortion and muscular trauma related to a congenital torticollis. This deformation likely resulted from shortage of amniotic f luid and confinement of the fetus dur-