Dental development and life history in living African and Asian apes

Kelley, Jay; Schwartz, Gary T.

doi:10.1073/pnas.0906206107

Cited by 96 publications

(73 citation statements)

References 38 publications

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“…The current study does not support suggestions that molar emergence in wild chimpanzees is systematically delayed relative to captive individuals (7,8); M1 emergence in living subjects from two captive studies ranges from 2.1 to 4.0 y with a mean age of ∼3.2 y (n = 53) (24)(25)(26). Four of our five wild infants erupted their M1s prior to the mean captive age.…”

Section: Discussioncontrasting

confidence: 45%

“…Nor is M1 emergence age consistent with Lee and colleagues' (44) "duration of lactation" metric (IBI minus gestation length) among our infant-mother dyads. The mothers of our focal animals evince IBIs that nearly span the mean ages of all great apes and humans (8) as well as most other chimpanzee communities (21-23), which would not be predicted from the relatively narrow range of our focal animals' M1 emergence ages.…”

Section: Discussionmentioning

confidence: 99%

“…Kelley and Schwartz (8) suggest that new M1 emergence ages derived from small samples of wild apes are consistent with patterns of IBI, age at first reproduction, and mean survivorship ages across great apes and humans. However, effectively nothing is known about variation in M1 emergence ages within populations or among species or subspecies of wild great apes (8,9). Moreover, most assessments of the predictive value of M1 emergence fail to consider normal variation in life history characters such as weaning age or interbirth intervals (20), which are influenced by ecology and maternal energetics (15,16,19,(21)(22)(23).…”

mentioning

confidence: 99%

“…Some have challenged the utility of tooth developmental data derived from captive animals for the reconstruction of hominin life history (7)(8)(9). Zihlman and colleagues (7) estimated maxillary tooth emergence ages from wild chimpanzee skeletons, which appeared to show later ages than living captive individuals.…”

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confidence: 99%

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First molar eruption, weaning, and life history in living wild chimpanzees

Smith

Machanda

Bernard³

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Understanding dental development in chimpanzees, our closest living relatives, is of fundamental importance for reconstructing the evolution of human development. Most early hominin species are believed to show rapid ape-like patterns of development, implying that a prolonged modern human childhood evolved quite recently. However, chimpanzee developmental standards are uncertain because they have never been based on living wild individuals. Furthermore, although it is well established that first molar tooth emergence (movement into the mouth) is correlated with the scheduling of growth and reproduction across primates broadly, its precise relation to solid food consumption, nursing behavior, or maternal life history is unknown. To address these concerns we conducted a photographic study of subadult chimpanzees (Pan troglodytes schweinfurthii) in Kanyawara, Kibale National Park, Uganda. Five healthy infants emerged their lower first molars (M1s) by or before 3.3 y of age, nearly identical to captive chimpanzee mean ages (∼3.2 y, n = 53). First molar emergence in these chimpanzees does not directly or consistently predict the introduction of solid foods, resumption of maternal estrous cycling, cessation of nursing, or maternal interbirth intervals. Kanyawara chimpanzees showed adult patterns of solid food consumption by the time M1 reached functional occlusion, spent a greater amount of time on the nipple while M1 was erupting than in the preceding year, and continued to suckle during the following year. Estimates of M1 emergence age in australopiths are remarkably similar to the Kanyawara chimpanzees, and recent reconstructions of their life histories should be reconsidered in light of these findings. human evolution | hominin life history | feeding ontogeny | primate nursing

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Section: Discussioncontrasting

confidence: 45%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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First molar eruption, weaning, and life history in living wild chimpanzees

Smith

Machanda

Bernard³

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…However, there is an extraordinary diversity of ape body sizes in the fossil record since the Miocene (24 to 5 Ma) and it is difficult to know which ones may represent ancestors of presentday apes and humans (32). Even if fossil evidence strongly suggested an increase in the size of the ancestors of present-day apes and humans in the past, it is not clear that body mass is a good correlate of life history parameters related to generation time (48). Although our number of data points is necessarily limited, we found no correlation between mass and generation time in present-day apes and humans, and the notably short generation time for the relatively large mountain gorilla is consistent with the expectation that highly folivorous (46) as well as more terrestrial (49) species are expected to reproduce earlier than more frugivorous, arboreal primates.…”

Section: Discussionmentioning

confidence: 96%

Generation times in wild chimpanzees and gorillas suggest earlier divergence times in great ape and human evolution

Langergraber

Prüfer

Rowney

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

501

349

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Fossils and molecular data are two independent sources of information that should in principle provide consistent inferences of when evolutionary lineages diverged. Here we use an alternative approach to genetic inference of species split times in recent human and ape evolution that is independent of the fossil record. We first use genetic parentage information on a large number of wild chimpanzees and mountain gorillas to directly infer their average generation times. We then compare these generation time estimates with those of humans and apply recent estimates of the human mutation rate per generation to derive estimates of split times of great apes and humans that are independent of fossil calibration. We date the human-chimpanzee split to at least 7-8 million years and the population split between Neanderthals and modern humans to 400,000-800,000 y ago. This suggests that molecular divergence dates may not be in conflict with the attribution of 6-to 7-million-y-old fossils to the human lineage and 400,000-yold fossils to the Neanderthal lineage.hominin | molecular dating | primate | speciation O ver 40 y ago, Sarich and Wilson used immunological data to propose that humans and African great apes diverged only about 5 million y ago, some three to four times more recently than had been assumed on the basis of the fossil record (1). Although contentious at the time (e.g., ref. 2), this divergence has since been repeatedly estimated from DNA sequence data at 4-6 million years ago (Ma) (3-8). However, this estimate is incompatible with the attribution of fossils older than 6 Ma to the human lineage. Although the assignment of fossils such as the ∼6 Ma Orrorin (9) and the 6-7 Ma Sahelanthropus (10) to the human lineage remains controversial (11), it is also possible that the divergence dates inferred from DNA sequence data are too recent.The total amount of sequence differences observed today between two evolutionary lineages can be expressed as the sum of two values: the sequence differences that accumulated since gene flow ceased between the lineages ("split time") and the sequence differences that correspond to the diversity in the common ancestor of both lineages. The extent of variation in the ancestral species may be estimated from the variance of DNA sequence differences observed across different parts of the genome between the species today, which will be larger the greater the level of variation in the ancestral population. By subtracting this value from the total amount of sequence differences, the sequence differences accumulated since the split can be estimated. The rate at which DNA sequence differences accumulate in the genome ("mutation rate") is needed to then convert DNA sequence differences into split times.In prior research, mutation rates have been calculated using species split times estimated from the fossil record as calibration points. For calculating split times between present-day humans and great apes, calibration points that assume DNA sequence differences between humans and orangutans...

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Growth, Development, and Life History in Hominin Evolution

Kelley¹,

Bolter²

2013

A Companion to Paleoanthropology

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Dental development and life history in living African and Asian apes

Cited by 96 publications

References 38 publications

First molar eruption, weaning, and life history in living wild chimpanzees

First molar eruption, weaning, and life history in living wild chimpanzees

Generation times in wild chimpanzees and gorillas suggest earlier divergence times in great ape and human evolution

Growth, Development, and Life History in Hominin Evolution

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