TY - JOUR
T1 - Life-History Inference in the Early Hominins Australopithecus and Paranthropus
AU - Kelley, Jay
AU - Schwartz, Gary
N1 - Funding Information:
Acknowledgments We thank the organizers of the symposium, Mike Plavcan and the late Charlie Lockwood, for inviting us to participate. Charlie will be sorely missed, both as a colleague and as a friend. We express particular appreciation to Chris Dean for engaging us in spirited debate about this topic and for carefully reading and commenting upon the draft manuscript, which led to numerous improvements. We also thank Tanya Smith for comments and Anne Bronikowski and the Dian Fossey Gorilla Fund for data on survivorship in Gorilla. We gratefully acknowledge financial support from the Institute of Human Origins.
PY - 2012/12
Y1 - 2012/12
N2 - The life histories of early hominins are commonly characterized as being like those of great apes. However, the life histories of the extant great apes differ considerably from one another. Moreover, the extent to which their life histories correlate with the two aspects of morphology used to infer the life histories of fossil species, brain size and dental development, has remained subject to debate. Increased knowledge of great ape life histories and, more recently, dental development -in particular ages at first molar emergence- now make it clearer that the latter is strongly associated with important life-history attributes, whereas brain size, as reflected by cranial capacity, is less informative. Here we estimate ages at M1 emergence in several infant/juvenile individuals of Australopithecus and Paranthropus based on previous estimates of ages at death, determined through dental histology. These are uniformly earlier than would be predicted either by adult cranial capacity or by comparison to ages at M1 emergence in free-living extant great apes. This suggests that either, 1) the life histories of the early hominins were faster than those of all extant great apes; 2) there was selection for rapid initial dental development and presumably early weaning, but that early hominin life histories were otherwise more prolonged and consistent with adult cranial capacities; or 3) the ages at death have been systematically underestimated, resulting in underestimates of the ages at M1 emergence. We investigate the implications of each of these alternatives and, where possible, explore evidence that might support one over the others.
AB - The life histories of early hominins are commonly characterized as being like those of great apes. However, the life histories of the extant great apes differ considerably from one another. Moreover, the extent to which their life histories correlate with the two aspects of morphology used to infer the life histories of fossil species, brain size and dental development, has remained subject to debate. Increased knowledge of great ape life histories and, more recently, dental development -in particular ages at first molar emergence- now make it clearer that the latter is strongly associated with important life-history attributes, whereas brain size, as reflected by cranial capacity, is less informative. Here we estimate ages at M1 emergence in several infant/juvenile individuals of Australopithecus and Paranthropus based on previous estimates of ages at death, determined through dental histology. These are uniformly earlier than would be predicted either by adult cranial capacity or by comparison to ages at M1 emergence in free-living extant great apes. This suggests that either, 1) the life histories of the early hominins were faster than those of all extant great apes; 2) there was selection for rapid initial dental development and presumably early weaning, but that early hominin life histories were otherwise more prolonged and consistent with adult cranial capacities; or 3) the ages at death have been systematically underestimated, resulting in underestimates of the ages at M1 emergence. We investigate the implications of each of these alternatives and, where possible, explore evidence that might support one over the others.
KW - Australopithecus
KW - Cranial capacity
KW - Dental histology
KW - Life history
KW - Paranthropus
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U2 - 10.1007/s10764-012-9607-2
DO - 10.1007/s10764-012-9607-2
M3 - Article
AN - SCOPUS:84869117211
SN - 0164-0291
VL - 33
SP - 1332
EP - 1363
JO - International Journal of Primatology
JF - International Journal of Primatology
IS - 6
ER -