Evolutionary Anthropology最新文献

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.

We propose that domestication is the result of interspecies cooperative breeding. Considering domestication as an outcome of cooperative breeding can explain how domestication occurs in both plants and animals, encompass cases of domestication that do not involve humans, and shed light on why humans are involved in so many domesticatory relationships. We review the cooperative breeding model of human evolution, which posits that care of human infants by alloparents enabled the evolution of costly human brains and long juvenile development, while selecting for tolerance of strangers. We then explore how human cooperation in the protection and provisioning of young plants and animals can explain the evolution of domestication traits such as changes in development; loss of aggressive, defensive, and bet-hedging aspects of the phenotype; and increased fertility. We argue that the importance of cooperative breeding to human societies has made humans especially likely to enter into interspecies cooperative breeding relationships.

Up to now, Allen and Bergmann's rules have been studied in modern humans by analyzing differences in limb length, height, or body mass. However, there are no publications studying the effects of latitude in the 3D configuration of the ribcage. To assess this issue, we digitally reconstructed the ribcages of a balanced sample of 109 adult individuals of global distribution. Shape and size of the ribcage was quantified using geometric morphometrics. Our results show that the ribcage belonging to tropical individuals is smaller and slenderer compared to others living in higher latitudes, which is in line with Allen and Bergmann's rules and suggests an allometric relationship between size and shape. Although sexual dimorphism was observed in the whole sample, significant differences were only found in tropical populations. Our proposal is that, apart from potential sexual selection, avoiding heat loss might be the limiting factor for sexual dimorphism in cold-adapted populations.

Smith and Wood reply to Villmoare and Kimbel regarding the scientific credibility of problems in paleoanthropology that require causal explanations for unique historical events.

Vertebrates exhibit sexual dimorphism in response to infectious diseases and in morbidity and mortality rates to various pathogens. Females are generally more immunocompetent than males, despite their increased reproductive burden and the immunosuppressive effects of gestation. In addition, females generally have lower incidences of cancer compared to males; however, they have higher rates of autoimmune disorders. These sex differences may be a result of life history differences, sexual selection, genetics, and/or the physiological effects of hormones. As highly social mammals with complex life histories, primates offer a unique opportunity to investigate the evolution of enhanced female immunocompetence. This review aims to examine the evidence of this immunity gap, understand current hypotheses for its evolution, and explore the potential role of X chromosome specific genes and heterozygosity within this framework.

Smith and Smith and Wood proposed that the human fossil record offers special challenges for causal hypotheses because “unique” adaptations resist the comparative method. We challenge their notions of “uniqueness” and offer a refutation of the idea that there is something epistemologically special about human prehistoric data. Although paleontological data may be sparse, there is nothing inherent about this information that prevents its use in the inductive or deductive process, nor in the generation and testing of scientific hypotheses. The imprecision of the fossil record is well-understood, and such imprecision is often factored into hypotheses and methods. While we acknowledge some oversteps within the discipline, we also note that the history of paleoanthropology is clearly one of progress, with ideas tested and resolution added as data (fossils) are uncovered and new technologies applied, much like in sciences as diverse as astronomy, molecular genetics, and geology.