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Smith L.W.,Duke University | Delgado R.A.,New York Consortium in Evolutionary Primatology | Delgado R.A.,University of Southern California
American Journal of Primatology

While the hominin fossil record cannot inform us on either the presence or extent of social and cognitive abilities that may have paved the way for the emergence of language, studying non-vocal communication among our closest living relatives, the African apes, may provide valuable information about how language originated. Although much has been learned from gestural signaling in non-human primates, we have not yet established how and why gestural repertoires vary across species, what factors influence this variation, and how knowledge of these differences can contribute to an understanding of gestural signaling's contribution to language evolution. In this paper, we review arguments surrounding the theory that language evolved from gestural signaling and suggest some important factors to consider when conducting comparative studies of gestural communication among African apes. Specifically, we propose that social dynamics and positional behavior are critical components that shape the frequency and nature of gestural signaling across species and we argue that an understanding of these factors could shed light on how gestural communication may have been the basis of human language. We outline predictions for the influence of these factors on the frequencies and types of gestures used across the African apes and highlight the importance of including these factors in future gestural communication research with primates. © 2013 Wiley Periodicals, Inc. Source

Gilbert C.C.,York College - The City University of New York | Gilbert C.C.,City University of New York | Takahashi M.Q.,New York Consortium in Evolutionary Primatology | Takahashi M.Q.,Columbia University | And 3 more authors.
Journal of Human Evolution

Associated cercopithecoid postcrania are rare in the Plio-Pleistocene fossil record, particularly in the case of South African karst cave sites. However, as clear postcranial differences between major papionin clades have been documented, it should be possible to assign isolated papionin postcrania to the Cercocebus/Mandrillus and Papio/Lophocebus/Theropithecus groups wherever sufficient anatomy is preserved. Here, we demonstrate that two partial humeri preserved at Taung, UCMP 56693 and UCMP 125898, are most likely attributable to the Cercocebus/Mandrillus and Papio/Lophocebus/Theropithecus clades, respectively. Univariate analyses (ANOVAs and t-tests) and multivariate analyses (discriminant function analyses) of humeral features, combined with a phylogenetic analysis of 24 humeral characters, all support our assessment. Given that the overwhelming number of craniodental specimens at Taung are attributable to two papionin taxa, Procercocebus antiquus (a member of the Cercocebus/Mandrillus clade) and Papio izodi (a purported fossil species of the modern genus Papio), we assign UCMP 56693 to Pr. antiquus and UCMP 125868 to P. izodi with a high degree of confidence. Implications for cercopithecoid evolution and biogeography are discussed, with a particular emphasis on these two fossil taxa. © 2015 Elsevier Ltd. Source

Bryer M.A.H.,New York Consortium in Evolutionary Primatology | Bryer M.A.H.,City University of New York | Chapman C.A.,McGill University | Chapman C.A.,Wildlife Conservation Society | And 5 more authors.
International Journal of Primatology

Most extant primates feed on insects to some degree, yet the nutritional contributions of insects to primate diets are poorly characterized. Like many small-bodied frugivorous primates, redtail monkeys (Cercopithecus ascanius) also eat insects. We quantified the nutritional contributions of insects to the diets of female redtail monkeys in Kibale National Park, Uganda, from July 2010 to June 2012 through full day follows (N = 64) using weight-based estimates of food intake. Female redtail monkeys targeted insects for 41 % of feeding bouts, plant reproductive parts (including ripe fruits, unripe fruits, flowers, seeds) for 15 % of feeding bouts, and leaves (including young leaves, mature leaves, leaf petioles, leaf buds) for 17 % of feeding bouts. However, females spent just under 10 % of feeding time on insects, in contrast to 42 % on plant reproductive parts and 39 % on leaves. Redtail monkeys fed primarily on solitary, as opposed to eusocial, insects. Identification of consumed insects is challenging, but of consumed insects that could be identified 74 % were cicadas (order Homoptera), 14 % caterpillars (order Lepidoptera), and 7 % long-horned grasshoppers (order Orthoptera). On a dry matter basis, insects were fairly low in fat (<10 %, except for caterpillars) and high in crude protein content (mean ca. 69 %) compared to other foods, and contained low levels of indigestible chitin. Because insects are small, an insect feeding bout is much shorter than a feeding bout on vegetation or fruit. Despite the small proportion of time spent feeding on insects, redtail monkeys obtained a mean of 24 % of their daily protein intake and 14 % of energy through insectivory, though intake varied widely across females. Our findings demonstrate that female redtail monkeys gain more nutrients than expected given that they spend <10 % of feeding time ingesting insects. The many primates that complement plant diet items with insects may gain substantial nutrition through minimal feeding time. © 2015, Springer Science+Business Media New York. Source

Hart J.A.,Lukuru Wildlife Research Foundation | Detwiler K.M.,Florida Atlantic University | Gilbert C.C.,York College - The City University of New York | Burrell A.S.,New York University | And 8 more authors.

In June 2007, a previously undescribed monkey known locally as "lesula" was found in the forests of the middle Lomami Basin in central Democratic Republic of Congo (DRC). We describe this new species as Cercopithecus lomamiensis sp. nov., and provide data on its distribution, morphology, genetics, ecology and behavior. C. lomamiensis is restricted to the lowland rain forests of central DRC between the middle Lomami and the upper Tshuapa Rivers. Morphological and molecular data confirm that C. lomamiensis is distinct from its nearest congener, C. hamlyni, from which it is separated geographically by both the Congo (Lualaba) and the Lomami Rivers. C. lomamiensis, like C. hamlyni, is semi-terrestrial with a diet containing terrestrial herbaceous vegetation. The discovery of C. lomamiensis highlights the biogeographic significance and importance for conservation of central Congo's interfluvial TL2 region, defined from the upper Tshuapa River through the Lomami Basin to the Congo (Lualaba) River. The TL2 region has been found to contain a high diversity of anthropoid primates including three forms, in addition to C. lomamiensis, that are endemic to the area. We recommend the common name, lesula, for this new species, as it is the vernacular name used over most of its known range. © 2012 Hart et al. Source

Frost S.R.,University of Oregon | Gilbert C.C.,York College - The City University of New York | Gilbert C.C.,City University of New York | Pugh K.D.,New York Consortium in Evolutionary Primatology | And 6 more authors.

Thumb reduction is among the most important features distinguishing the African and Asian colobines from each other and from other Old World monkeys. In this study we demonstrate that the partial skeleton KNM-ER 4420 from Koobi Fora, Kenya, dated to 1.9 Ma and assigned to the Plio-Pleistocene colobine species Cercopithecoides williamsi, shows marked reduction of its first metacarpal relative to the medial metacarpals. Thus, KNM-ER 4420 is the first documented occurrence of cercopithecid pollical reduction in the fossil record. In the size of its first metacarpal relative to the medial metacarpals, C. williamsi is similar to extant African colobines, but different from cercopithecines, extant Asian colobines and the Late Miocene colobines Microcolobus and Mesopithecus. This feature clearly links the genus Cercopithecoides with the extant African colobine clade and makes it the first definitive African colobine in the fossil record. The postcranial adaptations to terrestriality in Cercopithecoides are most likely secondary, while ancestral colobinans (and colobines) were arboreal. Finally, the absence of any evidence for pollical reduction in Mesopithecus implies either independent thumb reduction in African and Asian colobines or multiple colobine dispersal events out of Africa. Based on the available evidence, we consider the first scenario more likely. © 2015 Frost et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

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