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The Evolution of Man
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 Pleistocene Hominins as a Resource for Carnivores: A c. 500,000-Year-Old Human Femur Bearing Tooth-Marks in North Africa (Thomas Quarry I, Morocco)
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Abstract
In many Middle Pleistocene sites, the co-occurrence of hominins with carnivores, who both contributed to faunal accumulations, suggests competition for resources as well as for living spaces. Despite this, there is very little evidence of direct interaction between them to-date. Recently, a human femoral diaphysis has been recognized in South-West of Casablanca (Morocco), in the locality called Thomas Quarry I. This site is famous for its Middle Pleistocene fossil hominins considered representatives of Homo rhodesiensis. The bone was discovered in Unit 4 of the Grotte à Hominidés (GH), dated to c. 500 ky and was associated with Acheulean artefacts and a rich mammalian fauna. Anatomically, it fits well within the group of known early Middle Pleistocene Homo, but its chief point of interest is that the diaphyseal ends display numerous tooth marks showing that it had been consumed shortly after death by a large carnivore, probably a hyena. This bone represents the first evidence of consumption of human remains by carnivores in the cave. Whether predated or scavenged, this chewed femur indicates that humans were a resource for carnivores, underlining their close relationships during the Middle Pleistocene in Atlantic Morocco. Introduction
Large carnivores are present in almost all Plio-Pleistocene archaeological sites, and bone damage (tooth and cut marks) among the faunal deposits indicate their close coexistence with hominins [1–5]. The increase of meat and fat in the diet of early Homo (c. 1.9 My), not only had an impact on brain and molar size [6,7], but also on their eco-ethological relationships with other predators or scavengers. The infiltration of hominins into the carnivore guild may have resulted in different forms of interactions or co-evolutionary processes, including direct competition for resources as well as passive confrontations, dispersals, extinctions, partitioning of resources, dependency, commensalism and eventually domestication during the Late Pleistocene [8–13]. Changes in hominin subsistence strategies might be the result of these interactions. Meat providers or dangerous competitors, large predators are considered alternately as either facilitating, or reducing the success of the very first human dispersals [14–19]. Inversely, humans had significant role in the extinctions of various carnivores in North America at the end of the Pleistocene [20] or much earlier in the Lower Pleistocene of East Africa [12]. As another example, the drastic decrease of the sabre tooth cats and giant hyenas and the establishment of the modern-day carnivore guild in the Early Middle Pleistocene on both sides of the Mediterranean are contemporaneous with the first long-term hominin settlements [21–23,14,16]. At that time, hominins hunted in groups and relied on new effective weapons; these two improvements allowed them to slaughter larger gregarious preys and to handle encounters with dangerous competitors [24–29,9,10]. Still, this was a period of stiff competition between large carnivores and hominins and many Middle Pleistocene mixed assemblages containing materials modified by humans and a diverse array of carnivores are recorded (e.g. [30,31,11]).
Nevertheless, although during the Plio-Pleistocene hominins and carnivores shared the same landscapes and competed for resources and natural shelter, there is poor evidence of direct confrontation, such as serious or lethal bone damage, before the Upper Paleolithic, when carnivore hunting became widespread [32,33]. Two earlier cases have been reported: the SK 54 australopithecine cranium of Sterkfontein (South Africa) [1] and the CN42174b Neanderthal parietal fragment of Cova Negra (Spain) [34,35], which both bear two holes that match the spacing of the canines of a leopard and were described as representing large felids attacks. However, most of the purported cases of predation by carnivores on humans, or vice-versa, are mostly inferred from indirect data: taxa frequency, age of death, location of tooth-marks or cut-marks on the carcasses (primary or secondary access) [36–38]. Whether tooth-marks on human bones or cut-marks on carnivore bones, we can only identify consumption marks without confidently discriminating between hunted animals and scavenged carcasses. In Plio-Pleistocene sites, human remains showing tooth-marks are often associated with the rest of the fauna consumed by carnivores. Examples include, Swartkrans [1], FLK 22, FLK-NN1 and NN3 at Olduvai [39,40] in Africa. In the Middle and Upper Pleistocene of Eurasia, examples are more numerous including those of Zhoukoudian [41,42], Atapuerca (Sima de los Huesos) [43], Grotta Guattari [44,45], Rochelot [46,47], Rochers-de-Villeneuve [48], Grotte de la Tour [49], Les Pradelles [50], Gruta da Oliveira [51], and Grotte du Bison at Arcy-sur-Cure [52], among many others. Such associations may suggest either direct predation on humans or scavenging on their remains. In the early Middle Pleistocene (up to c.500 ky) of North Africa, successful large predators such as the sabre-tooth cat Homotherium, lived alongside leopards and lion-sized felids. These large cats were associated with increasingly modern canids and hyenids (e.g., Crocuta and Hyaena replacing Pliocrocuta), which were effective hunters and carcass consumers [53]. At that time, hyenids largely dominated carnivore spectra in caves as in open-air sites, whereas large canids (Lycaon and Canis) remained rare, unlike in the European carnivore guild [14,15,19], jackals (Lupulella) and foxes being more common. All these carnivores alternately occupied the living spaces with hominins and exploited the hunted or scavenged resources brought by their competitors [54]. Once again, there is no convincing evidence of carnivore action on Middle Pleistocene human remains in North Africa, although this hypothesis was put forward for the Sidi Abderrahmane fossils in Morocco [55,56], whose discovery in a supposed hyena den led Biberson to hypothesize a contribution by this large carnivore. A newly recognized Middle Pleistocene human femoral diaphysis from the stratigraphic Unit 4 of the Grotte à Hominidés at Thomas Quarry I, in Casablanca, Morocco, is the first definite example of this kind... Link: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0152284 |
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