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The timing of the dispersal of anatomically modern humans (AMH) out of Africa is a fundamental question in human evolutionary studies. Existing data suggest a rapid coastal exodus via the Indian Ocean rim around 60,000 years ago. We present evidence from Jebel Faya, United Arab Emirates, demonstrating human presence in eastern Arabia during the last interglacial. The tool kit found at Jebel Faya has affinities to the late Middle Stone Age in northeast Africa, indicating that technological innovation was not necessary to facilitate migration into Arabia. Instead, we propose that low eustatic sea level and increased rainfall during the transition between marine isotope stages 6 and 5 allowed humans to populate Arabia. This evidence implies that AMH may have been present in South Asia before the Toba eruption (1).

Diet changes are considered key events in human evolution. Most studies of early hominin diets focused on tooth size, shape, and craniomandibular morphology, as well as stone tools and butchered animal bones. However, in recent years, dental microwear and stable isotope analyses have hinted at unexpected diversity and complexity in early hominin diets. Some traditional ideas have held; others, such as an increasing reliance on hard-object feeding and a dichotomy between Australopithecus and Paranthropus, have been challenged. The first known evidence of C₄ plant (tropical grasses and sedges) and hard-object (e.g., seeds and nuts) consumption dates to millions of years after the appearance of the earliest probable hominins, and there are no consistent trends in diet change among these species through time.

The life history of Home sapiens is characterized by a lengthy period of juvenile dependence that requires extensive allocare, short interbirth intervals with concomitantly high fertility rates, and a life span much longer than that of other extant great apes. Although recognized as species-defining, the traits that make up human life history are also notable for their extensive within- and between-population variation, which appears to trace largely to phenotypic and developmental plasticity. In this review, we first discuss the adaptive origins of plasticity in life history strategy and its influence on traits such as growth rate, maturational tempo, reproductive scheduling, and life span in modern human populations. Second, we consider the likely contributions of this plasticity to evolutionary diversification and speciation within genus Home. Contrary to traditional assumptions that plasticity slows the pace of genetic adaptation, current empirical work and theory point to the potential for plasticity-induced phenotypes to \"lead the way\" and accelerate subsequent genetic adaptation. Building from this work, we propose a \"phenotype-first\" model of the evolution of human life history in which novel phenotypes were first generated by behaviorally or environmentally driven plasticity and were later gradually stabilized into species-defining traits through genetic accommodation. [PUBLICATION ABSTRACT]

There is a growing consensus in early hominin studies that savannas did not play a significant role in the emergence of human evolutionary processes. Early hominins have been reported to be associated with densely wooded environments and sometimes forest, thereby reducing the importance of a shift from closed to open ecosystems in shaping these processes. In the second half of the twentieth century, two versions of the savanna hypothesis emerged: one depicted savannas as grasslands, the other as seasonal mosaic environments. Research has shown that the former is no longer tenable, but an increasing amount of paleoecological information provides compelling support for the latter. Here a critical review of the available paleoecological evidence is presented, and it is concluded that the savanna hypothesis not only has not been falsified but its heuristics are stronger than ever before.

Paleolithic archaeologists conceptualize the uniqueness of Homo sapiens in terms of \"behavioral modernity,\" a quality often conflated with behavioral variability. The former is qualitative, essentialist, and a historical artifact of the European origins of Paleolithic research. The latter is a quantitative, statistically variable property of all human behavior, not just that of Ice Age Europeans. As an analytical construct, behavioral modernity is deeply flawed at all epistemological levels. This paper outlines the shortcomings of behavioral modernity and instead proposes a research agenda focused on the strategic sources of human behavioral variability. Using data from later Middle Pleistocene archaeological sites in East Africa, this paper tests and falsifies the core assumption of the behavioral-modernity concept--the belief that there were significant differences in behavioral variability between the oldest H. sapiens and populations younger than 50 kya. It concludes that behavioral modernity and allied concepts have no further value to human origins research. Research focused on the strategic underpinnings of human behavioral variability will move Paleolithic archaeology closer to a more productive integration with other behavioral sciences. [PUBLICATION ABSTRACT]

The \"expensive brain\" framework proposes that the costs of an increase in brain size can be met by any combination of increasing the total energy turnover or reducing energy allocation to other expensive functions, such as maintenance (digestion), locomotion, or production (growth and reproduction). Here, we explore its implications for human evolution. Using both comparative data on extant mammals and life-table simulations from wild extant apes, we show that primates with a hominoid lifestyle face a gray ceiling that limits their brain size, with larger values leading to demographic nonviability. We argue that cooperative care provides the most plausible exaptation for the increase in brain size in the Homo lineage. [PUBLICATION ABSTRACT]

Recent fossil and archaeological finds have complicated our interpretation of the origin and early evolution of genus Homo. Using an integrated data set from the fossil record and contemporary human and nonhuman primate biology, we provide a fresh perspective on three important shifts in human evolutionary history: (1) the emergence of Homo, (2) the transition between non-erectus early Homo and Homo erect us, and (3) the appearance of regional variation in H. erectus. The shift from Australopithecus to Homo was marked by body and brain size increases, a dietary shift, and an increase in total daily energy expenditure. These shifts became more pronounced in H. erectus, but the transformation was not as radical as previously envisioned. Many aspects of the human life history package, including reduced dimorphism, likely occurred later in evolution. The extant data suggest that the origin and evolution of Homo was characterized by a positive feedback loop that drove life history evolution. Critical to this process were probably cooperative breeding and changes in diet, body composition, and extrinsic mortality risk. Multisystem evaluations of the behavior, physiology, and anatomy of extant groups explicitly designed to be closely proxied in the fossil record provide explicit hypotheses to be tested on future fossil finds. [PUBLICATION ABSTRACT]

Models for the origin of the genus Homo propose that increased quality of diet led to changes in ranging ecology and selection for greater locomotor economy, speed, and endurance. Here, I examine the fossil evidence for postcranial change in early Homo and draw on comparative data from living mammals to assess whether increased diet quality has led to selection for improved locomotor performance in other lineages. Body mass estimates indicate early Homo, both males and females, were approximately 33% larger than australopiths, consistent with archeological evidence indicating an ecological change with the origins of our genus. However, many of the postcranial features thought to be derived in Homo, including longer hind limbs, are present in Australopithecus, challenging the hypothesis that early Homo is marked by significant change in walking and running performance. Analysis of energy budgets across mammals suggests that the larger body mass and increased diet quality in early Homo may reflect an increase in the hominin energy budget. Expanding the energy budget would enable greater investment in reproduction without decreasing energy available for larger brains or increased activity. Food sharing and increased adiposity, which decrease variance in food energy availability, may have been integral to this metabolic strategy.

East African paleoenvironmental data increasingly inform an understanding of environmental dynamics. This understanding focuses less on habitat reconstructions at specific sites than on the regional trends, tempo, and amplitudes of climate and habitat change. Sole reliance on any one indicator, such as windblown dust or lake sediments, gives a bias toward strong aridity or high moisture as the driving force behind early human evolution. A synthesis of geological data instead offers a new paleoenvironmental framework in which alternating intervals of high and low climate variability provided the dynamic context in which East African Homo evolved. The Oldowan behavioral record presents further clues about how early Homo and Homo erectus responded to East African environmental change. Shifting conditions of natural selection, which were triggered by climatic variability, helped shape the adaptability of Oldowan hominins. Together, the behavioral and environmental evidence indicates the initial adaptive foundation for the dispersal of H. erectus and the persistence of Homo. In particular, overall dietary expansion made possible by the making and transport of stone tools compensated for increased locomotor and foraging costs and provided effective behavioral-ecological responses to resource instability during the early evolution of Homo.

The evolution of modern human behavior was undoubtedly accompanied by neurological changes that enhanced capacities for innovation in technology, language, and social organization associated with working memory. Constructive memory integrates components of working memory in the medial prefrontal cortex to imagine alternative futures. Enhanced mental time travel permits long‐range strategic planning. Within this broadly conceived area of cognitive neuropsychology, I will focus on two stages of the evolution of cognitive faculties for planning. The first involves executing complex sequences of actions involving manufacture of multicomponent artifacts; the second involves enhanced planning through information sharing, which required the establishment of extended regional social interaction networks based on trust and cooperation. Both stages were probably accompanied by important innovations in grammatical speech.