Evolutionary Anthropology最新文献

The jaw-adductor muscles drive the movements and forces associated with primate feeding behaviors such as biting and chewing as well as social signaling behaviors such as wide-mouth canine display. The past several decades have seen a rise in research aimed at the anatomy and physiology of primate chewing muscles to better understand the functional and evolutionary significance of the primate masticatory apparatus. This review summarizes variation in jaw-adductor fiber types and muscle architecture in primates, focusing on physiological, architectural, and behavioral performance variables such as specific tension, fatigue resistance, muscle and bite force, and muscle stretch and gape. Paranthropus and Australopithecus are used as one paleontological example to showcase the importance of these data for addressing paleobiological questions. The high degree of morphological variation related to sex, age, muscle, and species suggests future research should bracket ranges of performance variables rather than focus on single estimates of performance.

Robert Broom, who is best known among vertebrate paleontologists for his research on mammal-like reptiles, was drawn into paleoanthropology because of his defense of Raymond Dart's interpretation of the Taung infant skull. Our contribution documents Robert Broom's background, his life and career, and how he became directly involved with human origins research in South Africa in the second and third decades of the 20thC. It focuses on the circumstances surrounding Broom's interest in what was being recovered at Sterkfontein, how Broom “discovered” the site of Kromdraai, and the fossil evidence that led to his 1938 paper announcing the discovery of a new hominin genus and species, Paranthropus robustus. It also summarizes subsequent discoveries assigned to P. robustus, and developments in interpretations of its evolutionary history. Broom was a complex character who combined remarkably “modern” interpretations of the early hominin fossil record, with decidedly idiosyncratic views about science and evolution, and attitudes to modern human variation that were overtly racist.

Sexual dimorphism is one of the main factors confounding attempts to generate sound alpha taxonomic hypotheses in the early hominin fossil record. To better understand how between-sex variation may confound alpha taxonomic assessments, we consider some of the factors that drive hard-tissue sexual dimorphism in extant primates. We review the socioecological correlates of body size sexual dimorphism, how sexual selection may be associated with craniofacial sexual dimorphism in the context of visual signaling, and how sex-specific patterns of growth and development in primates contribute to intra-specific variation. To illustrate how variation associated with inferred sexual dimorphism has the potential to confound alpha taxonomic assessments in early hominins, we focus on its impact on our understanding of a single taxon, Paranthropus boisei. We suggest that regions of the skeleton likely to be influenced by sexual selection should be avoided when generating alpha taxonomic hypotheses.

A debate has developed with regard to geological ages of hominin fossils attributed to Australopithecus africanus and Australopithecus prometheus in South African Plio-Pleistocene cave deposits. For the Sterkfontein caves (Members 2 and 4), cosmogenic nuclide isochron (¹⁰Be/²⁶Al) dating has yielded age estimates ranging from 3.4 to 3.7 million years ago (Ma). However, biochronological approaches using nonhominin primates suggest an alternative age range between 2 and 2.6 Ma. Based on a new method of hominin biochronology, Thackeray and Dykes have recognized that Sterkfontein Member 4 has a mean age of 2.76 Ma associated with a wide range (circa 2.0–3.5 Ma). In this study, the Sterkfontein skull and skeleton (StW 573), nicknamed “Little Foot” from Member 2 and attributed to A. prometheus, is reassessed. A regression model applied to estimate its age provides a hypothesized date of 3.6 Ma, which compares favorably with the existing cosmogenic dates.

A kiss has been a signal of special affection across continents and cultures for millennia. Between times and peoples, social norms invariably prescribe kissing to specific affiliations and contexts, implying deeper biological bases. Why the protruding of the lips and slight suction when touching another? Capuchin monkeys stick their fingers in their friends' eyes as sign of affection, why have humans developed kissing? Here I briefly review proposed hypotheses for the evolution of human kissing. Great ape social behavior suggests that kissing is likely the conserved final mouth-contact stage of a grooming bout when the groomer sucks with protruded lips the fur or skin of the groomed to latch on debris or a parasite. The hygienic relevance of grooming decreased over human evolution due to fur-loss, but shorter sessions would have predictably retained a final “kissing” stage, ultimately, remaining the only vestige of a once ritualistic behavior for signaling and strengthening social and kinship ties in an ancestral ape.

The evolution of Paleolithic stone tool technologies is characterized by gradual increase in technical complexity along with changes in the composition of assemblages. In this respect, the emergence of retouched-backed tools is an important step and, for some, a proxy for “modern” behavior. However, backed tools emerge relatively early and develop together with major changes in Middle-Upper Pleistocene stone tool technologies. We provide an updated review of the emergence and development of the “backing” concept across multiple chrono-cultural contexts and discuss its relationship to both the emergence of hafting and major evolutionary steps in the ergonomics of stone tool use. Finally, we address potential mechanisms of context-specific re-invention of backing based primarily on data from the late Middle Paleolithic of Western Europe.

The Trivers–Willard hypothesis predicts that mammalian parents in poor environmental conditions will favor the offspring sex with more reliable chance of reproductive success, which in humans is females. Three months following the onset of the COVID-19 pandemic in South Africa, England, and Wales, there were significant decreases in the sex ratio at birth (SRB) (male births/total live births). We analyzed this ratio with a seasonal autoregressive moving average model, and a logistic regression, using nationwide natality data for all singleton births in the United States from 2015 to 2021 (n = 25,201,620 total births). We identified no significant change in the sex ratio in either analysis. Rather, we observed marked differences in the sex ratio by maternal characteristics of race/ethnicity, age, and education, with more vulnerable groups having lower sex ratios. These findings suggest the SRB may be an important marker of reproductive vulnerability for disadvantaged groups in the United States.