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Mission - Hominin life histories

tooth microstructure

Life history studies, concerning the timing and energy invested into growth, reproduction, and death, are critical to understanding evolutionary processes in human evolution. Analyses of dental development, molar eruption, and age at death based on incremental features of the dentition are the most accurate means of identifying developmental change in the human fossil record. Dental development in humans and great apes begins prior to birth and continues throughout adolescence. Like many biological systems, hard tissue formation is characterized by a circadian rhythm. Developmental rate and time are permanently recorded by incremental lines in enamel and dentine, which remain unchanged in these tissues for millions of years.

Studies on Plio-Pleistocene hominids and Neanderthals have indicated that the relatively slow developmental rate and prolonged duration of modern human crown formation may be a fairly recent and unique development.

Beside an extended period of growth, humans display a particular pattern in brain development. Because of our adaptations to bipedalism and of the physiological cost of developing a very big adult brain, most of the brain growth occurs after birth in humans.

These adaptions have important implications for our understanding of hominid evolution and the origin of developmentally modern humans. This extended period of dental development, and by implication childhood, relates to social, biological, and cultural conditions necessary to support highly dependent children with prolonged opportunities for social learning in early childhood. The brain itself and cogntive abilities are shaped during this long developmental period. Recent studies in the Department of Human Evolution have demonstrated that this modern pattern existed in the earliest members of our own species (Homo sapiens).