Rapid dental development in a Middle Paleolithic Belgian Neanderthal

Abstract

The evolution of life history (pace of growth and reproduction) was crucial to ancient hominin adaptations. The study of dental development facilitates assessment of growth and development in fossil hominins with greater precision than other skeletal analyses. During tooth formation, biological rhythms manifest in enamel and dentine, creating a permanent record of growth rate and duration. Quantification of these internal and external incremental features yields developmental benchmarks, including ages at crown completion, tooth eruption, and root completion. Molar eruption is correlated with other aspects of life history. Recent evidence for developmental differences between modern humans and Neanderthals remains ambiguous. By measuring tooth formation in the entire dentition of a juvenile Neanderthal from Scladina, Belgium, we show that most teeth formed over a shorter time than in modern humans and that dental initiation and eruption were relatively advanced. By registering manifestations of stress across the dentition, we are able to present a precise chronology of Neanderthal dental development that differs from modern humans. At 8 years of age at death, this juvenile displays a degree of development comparable with modern human children who are several years older. We suggest that age at death in juvenile Neanderthals should not be assessed by comparison with modern human standards, particularly those derived from populations of European origin. Moreover, evidence from the Scladina juvenile and other similarly aged hominins suggests that a prolonged childhood and slow life history are unique to Homo sapiens.hominin ͉ human evolution ͉ life history ͉ ontogeny ͉ tooth growth

Dental evidence for ontogenetic differences between modern humans and Neanderthals

“…Long-period line periodicities for most juvenile specimens were observed with 0.7-μm phase contrast scans (SI Appendix, Figs. S12 and S13), except the Scladina individual, which was physically-sectioned (13) and later confirmed with synchrotron imaging. Crown formation time estimates for the Obi Rakhmat 1 individual were used for age-at-death calculation only (detailed below).…”

“…Studies of dental growth have revealed that Pliocene to Early Pleistocene hominin ontogeny was more rapid than that of recent humans (12,16,17), but data from limited Neanderthal samples continues to be vigorously debated (7,13,18). A paucity of information on dental development in hominins postdating Homo erectus, coupled with conflicting interpretations of Neanderthal ontogeny, complicates assessment of the modern human (fossil and recent Homo sapiens) and Neanderthal ancestral condition.…”

“…1, Table 1, and Movie S1). Furthermore, we reevaluate results obtained from single juveniles of both taxa (13,14) and contrast these expanded samples with radiographic and histological data from recent human populations. Although traditional histological methods are destructive, generally prohibiting comprehensive studies of rare fossil material, recent advances in synchrotron X-ray imaging now permit accurate 3D virtual histology (19,20).…”

“…Tooth histology, involving quantification of microscopic growth, is the most effective means of determining developmental rates, eruption ages, and age at death in juvenile hominins (12)(13)(14)(15). Studies of dental growth have revealed that Pliocene to Early Pleistocene hominin ontogeny was more rapid than that of recent humans (12,16,17), but data from limited Neanderthal samples continues to be vigorously debated (7,13,18).…”

The prehistory of compassion

“…Perhaps the large-brained species of Middle Pleistocene hominins, which the Salé and SH14 specimens belong to, had already acquired most of the human pattern. However, evidence has shown that later Neandertals still had more rapid dental development than extant Homo sapiens (20).…”