Les restes humains du Pliocène final et du début du Pléistocène inférieur de Dmanissi, Géorgie (1991–2000). I – Les crânes, D 2280, D 2282, D 2700

Abstract

Since 1991, several human remains: 5 skulls, 4 mandibles and numerous postcranial fragments have been discovered on the Dmanissi prehistoric open site. It is an exceptional discovery due to the stratigraphical, paleontological and cultural context, which is well known and accurately well dated (Upper Pliocene–Early Pleistocene). Most of the hominids discovered in the level V and VI are dated between 1.81 My (level V) and 1.77 My (level VI) corresponding to a 40,000 years period. The assemblage of fossil human remains is peculiar due to (1) the quality of bone representation (distinct parts of the skeleton are preserved: skull, thorax, upper and lower limbs, belt), (2) the high degree of bone preservation (skulls and long bones are entire, rarely broken or crushed), (3) the diversity age at death estimated for each of the 5 individuals (3 adults, 1 young adult, 1 adolescent of both sexes). The study dealing with the first discovered mandibles and skulls has begun with Leo Gabounia since 1991 and represents several interests: 1) a paleoanthropological interest: the Dmanissi skulls are characterized by their small size; they are short, narrow and low. The skullcaps are less elevated than those of the Homo erectus group and even those of Homo ergaster. They are more elevated than those of Homo habilis and very close to Homo rudolfensis. The elevation and the transversal development of the middle part of the skull in the parietotemporal region are more significant: the Dmanissi specimens are intermediate between Homo habilis and Homo ergaster. In term of cranial capacity, a similar trend is observed. Generally speaking, the skull is slender. The vault is more flat than in Homo erectus, the frontal bone is less developed, divergent and the postorbital constriction is strong. The temporal bone is long, flat and the mastoid part is short. The upper part of the occipital bone is low and narrow. Crests are thin, less developed than in the Homo erectus group. The superior temporal crests are in a high position and a torus angularis is present on the adult-male specimen. The glenoid cavity is large with strong edges. The petrotympanic region is slender with a tympanic circle individualized and it shows a horizontal rotation in a posterior position, which is distinct from Homo erectus. The orthognathic trend of the face distinguishes the Dmanissi specimens from the early Pleistocene hominids ( Homo habilis, Homo ergaster) and from the first Eurasian Homo erectus. Nevertheless, the subnasal region of the face is projected. The morphology of the mid-face, showing a developed pillar of the canine, an inframalar incurvation and an anterior position of the root of the zygomaticomaxillary crest, suggests strong masticatory stress. Considering the overall morphology, cranial and metrical features, the Dmanissi fossil skulls are intermediate to the Homo habilis- rudolfensis group and Homo ergaster while they are closer to the former and peculiarly to Homo rudolfensis (ER 1470). However, the Dmanissi fossil skulls are distinct from Homo rudolfensis by numerous features and among them: by their large maximum cranial width ( Euryon– Euryon), the posterior rotation of their petrotympanic structure and the strong development of the pillar of their canine. Due to the gracility of their face, the narrowness of their occipital bone, and their cranial base pattern (mastoid region and petrotympanic structure), the Dmanissi fossil skulls are different from the Homo erectus group: 2) the abundance of the human fossils discovered in Dmanissi site provides information about the biodiversity of these hominids with the establishment of the morphological features related to either growth or sexual patterns: 3) compared to modern humans, the Dmanissi fossil skulls seem to follow a different growth pattern. The present study of the fossil skulls discovered is a pioneer step. Indeed, the Dmanissi site has yielded the oldest evidences of the first settlements in Eurasia, which were, until now, attributed to Homo erectus. The Dmanissi fossil skulls are close to the Homo habilis-rudolfensis African group. We attribute these hominids to Homo georgicus.