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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...

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The middle Paleolithic stratigraphic sequence of Les Pradelles (Charente, France) spans from the end of Marine Isotope Stage (MIS) 4 until the middle of MIS 3. Micromammal remains are present in all the stratigraphic levels, offering a rare opportunity to address the questions of both environmental and climatic fluctuations throughout this period. Climate modes were studied through the taphonomy, biodiversity and oxygen isotope compositions of phosphate (δ18O p ) from 66 samples of rodent tooth enamel. The δ18O p values from the lower sedimentary levels provide summer mean air temperatures of 19 ± 2°C (level 2/1) and of 16 ± 2°C (levels 2A, 2B and 4A). Within the middle of sequence (level 4B), a paleobiodiversity change can be identified with an increase of Dicrostonyx torquatus, which is associated with the largest amplitude in δ18O p values and the highest maximal δ18O p values. At the top of the sequence (level 5-2), a biodiversity change is observed with the increase of Microtus arvalis, but without any change in δ18O p values. The association of cold rodent species with unexpected high and large amplitudes in the δ18O p values of their teeth, possibly indicative of aridity, suggests their deposition during a Heinrich event.

This study reports on a sample of 12 modern human incisors (from two archaeological sites) that were viewed with a scanning electron microscope and whose perikymata were counted. These 12 incisors more than doubles the previously published sample size of modern human incisors that have served as the published standard for perikymata number in human incisors and have been employed to define taxonomic relationships in fossil hominids. All previously published fossil specimens fall within the expanded range of modern human perikymata counts and can no longer be considered distinctively nonhuman in dental formation time.Five neandertal incisors from the Krapina site in Croatia, Yugoslavia, were also examined. These incisors substantially expand the previous data base for counts of perikymata in Homo sapiens neanderthalensis, likewise overlapping the previously published modern human range.Finally, the validity of methods that have been employed for deriving crown formation times from perikyrnata counts in fossil hominines is called into question. Utilizing the presently known perikymata ranges for modern humans, these methods do not predict the range of known crown formation times of modern humans as assessed from studies of living children.

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