Sexual dimorphism in the face of Australopithecus africanus

Lockwood, Charles A.

doi:10.1002/(sici)1096-8644(199901)108:1<97::aid-ajpa6>3.3.co;2-f

Cited by 35 publications

(95 citation statements)

References 47 publications

(83 reference statements)

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“…The high (near gorilla) levels of sexual dimorphism in all early hominins for which sufficient data are available, including Australopithecus (McHenry, 1986;Lockwood et al, 1996;Lockwood, 1999;Ward et al, 2001) and Paranthropus (Silverman et al, 2001), imply that strong sexual dimorphism in body size characterized the LCA. However, these taxa appeared millions of years after the LCA, so the reconstruction of the LCA as highly sexually dimorphic must await confirmation from earlier taxa.…”

Section: Reconstruction Of the Last Common Ancestor Of Pan And Homomentioning

confidence: 94%

Origin of human bipedalism: The knuckle-walking hypothesis revisited

Richmond

Begun

Strait

2001

Am. J. Phys. Anthropol.

116

191

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Some of the most long-standing questions in paleoanthropology concern how and why human bipedalism evolved. Over the last century, many hypotheses have been offered on the mode of locomotion from which bipedalism originated. Candidate ancestral adaptations include monkey-like arboreal or terrestrial quadrupedalism, gibbon-or orangutan-like (or other forms of) climbing and suspension, and knuckle-walking. This paper reviews the history of these hypotheses, outlines their predictions, and assesses them in light of current phylogenetic, comparative anatomical, and fossil evidence. The functional significance of characteristics of the shoulder and arm, elbow, wrist, and hand shared by African apes and humans, including their fossil relatives, most strongly supports the knuckle-walking hypothesis, which reconstructs the ancestor as being adapted to knuckle-walking and arboreal climbing. Future fossil discoveries, and a clear understanding of anthropoid locomotor anatomy, are required to ultimately test these hypotheses. If knucklewalking was an important component of the behavioral repertoire of the prebipedal human ancestor, then we can reject scenarios on the origin of bipedalism that rely on a strictly arboreal ancestor. Moreover, paleoenvironmental data associated with the earliest hominins, and their close relatives, contradict hypotheses that place the agents of selection for bipedality in open savanna habitats. Existing hypotheses must explain why bipedalism would evolve from an ancestor that was already partly terrestrial. Many food acquisition and carrying hypotheses remain tenable in light of current evidence.

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Section: Reconstruction Of the Last Common Ancestor Of Pan And Homomentioning

confidence: 94%

Origin of human bipedalism: The knuckle-walking hypothesis revisited

Richmond

Begun

Strait

2001

Am. J. Phys. Anthropol.

116

191

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“…Aust. robustus, from southern Africa, may have had pronounced sex differences in reproductive maturation, consistent with one-male polygyny (Lockwood et al, 2007), and appeared to exhibit sexually dimorphic craniofacial anatomy, also consistent with some degree of polygyny (Lockwood, 1999). Attempts to draw additional inferences concerning hominin sexuality have used the study of digit ratios (Nelson et al, 2011) and other aspects of craniofacial dimorphism (Schaefer et al, 2004), but without clear inferences.…”

Section: Early Hominin and Australopithecine Sexualitymentioning

confidence: 99%

Evolution and human sexuality

Gray

2013

American J Phys Anthropol

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The aim of this review is to put core features of human sexuality in an evolutionary light. Toward that end, I address five topics concerning the evolution of human sexuality. First, I address theoretical foundations, including recent critiques and developments. While much traces back to Darwin and his view of sexual selection, more recent work helps refine the theoretical bases to sex differences and life history allocations to mating effort. Second, I consider central models attempting to specify the phylogenetic details regarding how hominin sexuality might have changed, with most of those models honing in on transitions from a possible chimpanzee-like ancestor to the slightly polygynous and long-term bonded sociosexual partnerships observed among most recently studied hunter-gatherers. Third, I address recent genetic and physiological data contributing to a refined understanding of human sexuality. As examples, the availability of rapidly increasing genomic information aids comparative approaches to discern signals of selection in sexuality-related phenotypes, and neuroendocrine studies of human responses to sexual stimuli provide insight into homologous and derived mechanisms. Fourth, I consider some of the most recent, large, and rigorous studies of human sexuality. These provide insights into sexual behavior across other national samples and on the Internet. Fifth, I discuss the relevance of a life course perspective to understanding the evolution of human sexuality. Most research on the evolution of human sexuality focuses on young adults. Yet humans are sexual beings from gestation to death, albeit in different ways across the life course, and in ways that can be theoretically couched within life history theory. Am J Phys Anthropol 57:94-118, 2013. V C 2013 Wiley Periodicals, Inc.The aim of this review is to put core features of human sexuality in an integrative, evolutionary light. Given the central importance of sexuality to the evolutionary imperative-reproductive success-there is strong theoretical impetus for understanding how evolution has shaped human sexuality in the past, and for how the influence of past selective forces continue to manifest in the present. For biological anthropologists, interdisciplinary social and biomedical scientists, and even wider audiences, questions about human sexuality can be among the most compelling and meaningful, another reason to try informing answers to fundamental questions of human sexuality with the most scientifically supported and current views. An understanding of human sexuality is central to topics as diverse as predicting the dynamics of a sexually transmitted infection (STI) outbreak to the reasons why people pour so much of their time and resources into mating effort. Human sexuality, as much as any other topical focus within biological anthropology, warrants ongoing evolutionary scrutiny.For several reasons, this is arguably an opportune time for providing a current overview of the evolution of human sexuality. For one, many of the foundati...

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“…In most species, measurements of the brain case, basicranium, and orbits tend to show less dimorphism than measurements of the face and jaws ( Fig. 4; Leigh and Cheverud, 1991;Ravosa, 1991;Ravosa and Ross, 1994;Corner and Richtsmeier, 1991Masterson, 1997;Masterson and Hartwig, 1998;Lockwood, 1999;Plavcan, in press). However, measurements of a single bone, such as the mandible, can show substantially different degrees of dimorphism within and among species.…”

Section: "Reverse Dimorphism"mentioning

confidence: 99%

“…This observation is intriguing for those interested in understanding hominid dimorphism, because it implies that the intense craniofacial dimorphism of some hominids is associated with even greater body mass dimorphism than formerly suspected (cf. Lockwood, 1999).…”

Section: "Reverse Dimorphism"mentioning

confidence: 99%

Sexual dimorphism in primate evolution

Plavcan

2001

Am. J. Phys. Anthropol.

164

175

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Sexual dimorphism is a pervasive phenomenon among anthropoid primates. Comparative analyses over the past 30 years have greatly expanded our understanding of both variation in the expression of dimorphism among primates, and the underlying causes of sexual dimorphism. Dimorphism in body mass and canine tooth size is familiar, as is pelage and "sex skin" dimorphism. More recent analyses are documenting subtle differences in the pattern of skeletal dimorphism among primates. Comparative analyses have corroborated the sexual selection hypotheses, and have provided a more detailed understanding of the relationship between sexual selection, natural selection, and mating systems in primates. A clearer picture is emerging of the relative contribution of various selective and nonselective mechanisms in the evolution and expression of dimorphism. Most importantly, recent studies have shown that dimorphism is the product of changes in both male and female traits. Developmental studies demonstrate the variety of ontogenetic pathways that can lead to dimorphism, and provide additional insight into the selective mechanisms that influence dimorphism throughout the lifetime of an animal. Evidence from the fossil record suggests that dimorphism probably evolved in parallel twice, and the dimorphism in some extinct hominoids probably exceeded that of any living primate. Our advances in understanding the behavioral/ecological correlates of dimorphism in living primates have not improved our ability to reconstruct social systems in extinct species on the basis of dimorphism alone, beyond the inference of polygyny or intense male-male competition. However, our understanding of the behavioral/ecological correlates of growth and development, and of the expression of dimorphism as a function of separate changes in male and female traits, offers great potential for inferring evolutionary changes in behavior over time

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Sexual dimorphism in the face of Australopithecus africanus

Cited by 35 publications

References 47 publications

Origin of human bipedalism: The knuckle-walking hypothesis revisited

Origin of human bipedalism: The knuckle-walking hypothesis revisited

Evolution and human sexuality

Sexual dimorphism in primate evolution

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