title: Dental ontogeny in pliocene and early pleistocene hominins.
abstract: Until recently, our understanding of the evolution of human growth and development derived from studies of fossil juveniles that employed extant populations for both age determination and comparison. This circular approach has led to considerable debate about the human-like and ape-like affinities of fossil hominins. Teeth are invaluable for understanding maturation as age at death can be directly assessed from dental microstructure, and dental development has been shown to correlate with life history across primates broadly. We employ non-destructive synchrotron imaging to characterize incremental development, molar emergence, and age at death in more than 20 Australopithecus anamensis, Australopithecus africanus, Paranthropus robustus and South African early Homo juveniles. Long-period line periodicities range from at least 6-12 days (possibly 5-13 days), and do not support the hypothesis that australopiths have lower mean values than extant or fossil Homo. Crown formation times of australopith and early Homo postcanine teeth fall below or at the low end of extant human values; Paranthropus robustus dentitions have the shortest formation times. Pliocene and early Pleistocene hominins show remarkable variation, and previous reports of age at death that employ a narrow range of estimated long-period line periodicities, cuspal enamel thicknesses, or initiation ages are likely to be in error. New chronological ages for SK 62 and StW 151 are several months younger than previous histological estimates, while Sts 24 is more than one year older. Extant human standards overestimate age at death in hominins predating Homo sapiens, and should not be applied to other fossil taxa. We urge caution when inferring life history as aspects of dental development in Pliocene and early Pleistocene fossils are distinct from modern humans and African apes, and recent work has challenged the predictive power of primate-wide associations between hominoid first molar emergence and certain life history variables.
authors.affiliation: Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America.
authors.forename: Tanya M
authors.initials: TM
authors.lastname: Smith
authors.affiliation: ESRF-The European Synchrotron, Grenoble, France.
authors.forename: Paul
authors.initials: P
authors.lastname: Tafforeau
authors.affiliation: Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America; ESRF-The European Synchrotron, Grenoble, France; Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
authors.forename: Adeline
authors.initials: A
authors.lastname: Le Cabec
authors.affiliation: Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America; ESRF-The European Synchrotron, Grenoble, France; Paul Scherrer Institut, Swiss Light Source, Villigen, Switzerland.
authors.forename: Anne
authors.initials: A
authors.lastname: Bonnin
authors.affiliation: Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America; ESRF-The European Synchrotron, Grenoble, France; Département Ecologie et Gestion de la Biodiversité, UMR 7179 CNRS, Muséum National d'Histoire Naturelle, Paris, France.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Houssaye
authors.affiliation: ESRF-The European Synchrotron, Grenoble, France; Laboratoire de Géologie, UMR 5276 CNRS, Université Claude Bernard Lyon 1, Villeurbanne, France.
authors.forename: Joane
authors.initials: J
authors.lastname: Pouech
authors.affiliation: Dipartimento di Biologia, Università di Firenze, Firenze, Italy.
authors.forename: Jacopo
authors.initials: J
authors.lastname: Moggi-Cecchi
authors.affiliation: Department of Earth Sciences, National Museums of Kenya, Nairobi, Kenya.
authors.forename: Fredrick
authors.initials: F
authors.lastname: Manthi
authors.affiliation: Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: Carol
authors.initials: C
authors.lastname: Ward
authors.affiliation: Department of Orthodontics, University of Bordeaux II, Bordeaux, France.
authors.forename: Masrour
authors.initials: M
authors.lastname: Makaremi
authors.affiliation: Centre for Anthropological Research, University of Johannesburg, Johannesburg, South Africa.
authors.forename: Colin G
authors.initials: CG
authors.lastname: Menter
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005580:Fossils; D015186:Hominidae; D014070:Tooth