Patterns of ontogeny in human evolution: Evidence from dental development

Abstract

An understanding of the patterns of maturation that characterize earlier hominines would markedly increase our understanding of human evolution. Earlier reports suggesting that the australopithecines had a pattern of growth and development similar to that of modern humans have been challenged in recent years by a variety of studies. These studies have focused on dental enamel microstructure in attempts to characterize the time frame of enamel calcification. When the latter are combined with data on root development and the sequence of dental calcification and eruption, a picture emerges that attempts to characterize modern human, early hominine,l and ape dental maturation.One of the major features that distinguish modern humans from other hominoids is the increased length of the childhood dependency period. Many writers have looked at this time as an important element in the basic adaptive strategy of humans (Gould, 1976;Dobzhansky, 1962;Mann, 1972;Lovejoy, 1981). A prolonged dependency period provides time for the transmission of complex information about the environment, its resources, and the methods of resource procurement from one generation to another. A lengthened time of dependency can permit the young to internalize information about a number of different, seasonally exploited habitats and the techniques most useful in finding and harvesting the resources in each area. Prolonged dependency also provides time for the young to learn the cues underlying the successful employment of the vast repertoire o f social hehaviorq that govern the peaceful and harmonious interactions of members of a society. It is possible that even the development of language is founded on the lengthened learning period of childhood.The precise biological mechanisms that were modified in the course of human evolution to bring about the prolongation of the dependency period are unknown, although Gould (1976) suggests that a relatively small number of changes in the regulatory genes controlling ontogenetic processes would be all that was necessary. Holloway (1969) has argued that the adaptive value of a prolonged time of maturation need not be directly related to an increase in brain size. In this view, an enlarged parietal association cortex, which he has described in early hominine endocasts (Holloway, 1981(Holloway, , 1983(Holloway, , 1984(Holloway, , 1985 Holloway and Kimbel, 1986; but see 'In this paper, we follow Weiss (1987) and Weiss and Mann (1990) in employing the subfamily IIomininae, rather than the family Hominidae, to describe humans and our close immediate ancestors and relatives. 0 1990 Wiley-Liss, Inc. PHYSICAL, ANTHROPOI,OGY lV0l 33,1990 Falk, 1987, for a contrasting view), would provide the essential neurological foundation for an extended childhood dependency to evolve. An understanding of when the prolonged childhood dependency period appeared in hominine evolution would be extremely useful for our comprehension of human evolution. In 1948 Dart initially suggested that the South African australop...

Dental maturational sequence and dental tissue proportions in the early Upper Paleolithic child from Abrigo do Lagar Velho, Portugal

“…Based on the same Bayesian statistical approach, an analogous result applies to the Roc de Marsal 1 Neandertal child (10), but not to the La Madeleine 4 late Upper Paleolithic child (24). In this respect, the mixed dentitions of the Neandertal and Gravettian individuals share a relatively delayed incisor calcification and/or a relative developmental advancement of the molars, a condition rarely if ever found in recent human populations (33,34).…”

“…The process of relative dental mineralization is quite variable in Late Pleistocene and post-Pleistocene populations (1,6,30,33,(35)(36)(37)(38)(39)). An extensive radiographic study of immature fossil dentitions has recorded numerous similarities in relative maturational patterns of the permanent teeth between Neandertals (∼130-35 ka BP) and Upper Paleolithic specimens (∼34-11 ka BP) from Europe and southwest Asia (1, 39).…”

A modern human pattern of dental development in Lower Pleistocene hominids from Atapuerca-TD6 (Spain)

“…Nevertheless, the M2/M3 relative development is a useful feature to distinguish both the great apes and modern human patterns (23,24). Taking into account the data reported by Anderson et al (12) for the mean age of attainment of mineralization stages, hominids 1 and 3 from TD6 exhibit a certain advancement of M3 calcification with regard to M2.…”

Humanity from African Naissance to Coming Millennia

“…Although these conclusions are consistent, even when different methods of approaching the problem are used, some students have pointed out that the extent of variability in the dental developmental patterns of modern humans is so broad that australopithecines can easily be accommodated within this range (Mann, Lampl & Monge, 1990). The issue of variability of dental developmental patterns within a single fossil species is thus of crucial importance if we wish to provide a basis for understanding the differences between taxa in terms of life history parameters.…”

“…That is, as far as patterns of dental development are concerned, Australopithecus recalls a situation similar to that observable in living apes, whereas Paranthropus shows patterns of development in some respects similar to those of modern humans. In both groups, however, the chronology of dental development appears to have been shorter than that of modern humans, and more similar to modern apes, with some differences between the two groups.Although these conclusions are consistent, even when different methods of approaching the problem are used, some students have pointed out that the extent of variability in the dental developmental patterns of modern humans is so broad that australopithecines can easily be accommodated within this range (Mann, Lampl & Monge, 1990). The issue of variability of dental developmental patterns within a single fossil species is thus of crucial importance if we wish to provide a basis for understanding the differences between taxa in terms of life history parameters.…”