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A matter of fat: Hunting preferences affected Pleistocene megafaunal extinctions and human evolution
Abstract
The longstanding debate over human contribution to Pleistocene megafauna extinctions motivates our examination of plausible hunting behaviors that may have impacted prey populations. Prey size declines during the Pleistocene have been proposed as a unifying selecting agent of human evolution. Here, we identify prey selection criteria and exploitation patterns that could have increased the extinction risk for targeted species. Limited protein metabolism capacity in humans is proposed to have led to a focus on fat-rich prey, primarily large and prime adults, and selective exploitation of fatty body parts. Such behaviors may have made human-hunted species more vulnerable to population decline due to human predation alone or in combination with environmental changes. We contextualize this hypothesized mechanism within modern evolutionary theory, noting alignment with Niche Construction Theory as an explanation for the directional changes in human physiology and culture over time. The well-evidenced trend of brain expansion provides historical continuity with longer-term primate evolution, meeting recent calls for greater emphasis on ancestral connections in evolutionary models.
Supplementary resource (1)
... recki complex" [3,98]. This has revived the suggestion that megafauna, particularly Palaeoloxodon, succumbed to hominin overhunting during this period [30,44]. However, unlike much of the New World, where debates on the overkill hypothesis rely on a plethora of megafaunal and associated archeological remains from more exhaustive researched contexts [99], the African Middle Pleistocene record presents an enigma whose resolution requires evidence from various sources. ...
... Our results favor the scenario where P. recki recki did not die out but adapted, in the form of P. jolensis, to changing climatic and environmental conditions coinciding with the Acheulean-MSA transition. If hominins were not responsible for the extinction of P. recki recki, at the end of the Acheulean, it is possible that they were ultimately responsible for the final demise of Palaeoloxodon during the MSA [30]. However, we note that there is no clear evidence of elephant butchery in any of the sites sampled for this study, or for that matter, any other Awash basin sites of the period. ...
The timing, cause, and magnitude of mammalian extinctions during the African Middle Pleistocene remain largely unresolved. The demise of Elephas/Palaeoloxodon recki, a lineage that had a great geographic and temporal span, represents a particularly enigmatic case of megafaunal extinction. Previous studies of Early Pleistocene fossil material have proposed that this lineage was a strict C4-grazer, with its dietary specialization causing its extinction during a period of climatic instability that coincided with the Late Acheulean. Others have associated its disappearance with overhunting by hominins during the same period. We contribute to this debate by analyzing carbon and oxygen isotope data from the tooth enamel of late Early and Middle Pleistocene Palaeoloxodon specimens from various localities in the Afar Rift. To contextualize the isotopic data of Palaeoloxodon within its broader ecosystem, we also provide data from non-elephant species. Carbon isotope values indicate that while C4 plants dominated diets, varying amounts of C3 vegetation were also consumed throughout this period. Oxygen isotope values reflect an initial focus on stable water sources that were later broadened to include transient sources. Serially sampled teeth of P. cf. recki recki from Late Acheulean contexts in the Megenta research area show no significant seasonal shifts in δ¹³C or δ¹⁸O values, even during a period of heightened climatic instability regionally. Taken together, our results suggest that Palaeoloxodon was capable of flexibility in diet and drinking habits which belies its morphological specializations. Our results do not support the idea that an inability to adapt to climatic instability caused the extinction of P. recki recki during the Late Acheulean. There is also currently no solid evidence that hominin hunting activities were the cause. However, we cannot discount the potential cumulative impact of climatic-induced environmental pressures and advancements in hominin hunting technologies during the early Middle Stone Age on the eventual extinction of the Palaeoloxodon lineage during the Middle–Late Pleistocene interface.
This thesis uses a biosocial anthropological approach to explore the wide variety of human-environmental interactions exhibited by the Shuar of the Ecuadorian Amazon. Based on 10 months of ethnographic inquiry and deploying a comparative and evolutionary perspective, this thesis focuses primarily on the holistic nature of ancient subsistence patterns. I delve into the adaptive strategies exhibited by the contemporary Shuar and attempt to delineate the socio-ecological, ritual and cosmological significance of these patterns of behaviour. I suggest how subsistence adaptations, like hunting, which have been greatly diminished in the Shuar communities, nevertheless reveal particular forms of cross-species interactions likely deeply rooted in coevolutionary processes. As clearly indicated by informants' oral histories, hunting patterns and meat-eating behaviour show complex trophic, socio-structural and ritual associations between humans and animal taxa. I then hypothesise that food taboos against eating particular animals (mostly large mammals) may have functioned as mechanisms for the preservation of prey and likely arose from ancient relationships with extinct megafauna. Further, concerning horticulture, a subsistence strategy still practised by the Shuar, I reveal how specific forms of human-plant interactions, such as those with Manihot esculenta Crantz and Guadua spp., inform patterns of patterns of growth, fertility and reproduction. This Amazonian form of human-plant coevolution exhibited by traditional horticulture underscores, in principle, basic and higher-order relational processes exemplified by the biosocial, ritual, ontological, and myth-cosmological associations between organismic kingdoms. Concerning the use of medicinal and psychoactive plants, I show how these kinds of botanical knowledge frequently intersect, thus representing adaptive behaviours highly dependent on embodied and cognitive engagements with plant materials. Both conceived as elementary forms of cure and primary triggers of metaphysical formulations, relationships with these elements of the plant kingdom are likely to be well-embedded in our evolutionary history. Lastly, the thesis' attempt at cross-species comparisons linked to different evolutionary periods (i.e., archaic hominins, extant forager-horticulturalists and non-human primates) may shed new light on the nature of complex adaptive patterns exhibited by Indigenous peoples in general and the Shuar in particular.
Most beef cattle in the US are feedlot-finished where intensive feeding of grains is used to increase weight and yield; however, a minority are raised in grass-fed operations that use exclusive pasture, rangeland, and hay for feeding, possibly leading to benefits for the land, soil, ecosystems, forages, and the meat itself. These operations use a variety of methods, and the goal of this was to recognize differences in the soil and forage metrics to help understand the resulting meat fatty acid composition and mineral content. We collected these samples from 78 sets of farmers while testing 25 sets of grain-fed controls, usually purchased from a store. We found major differences in organic matter between beef pasture soil and corn field soil and in the fatty acid content of forage and grains. These differences were highlighted with better fatty acid composition and mineral content in grass-fed meat. These results show the variability in beef operations across a range of variables, providing valuable insights into how different feeding practices impact the quality of beef and the environment.
Biased skeletal part representation is a key element for making inferences about transport decisions, carcass procurement, and use patterns in anthropogenic accumulations. In the absence of destructive taphonomic processes, it is often assumed that the abundance of different anatomical portions represents selective transport and discard patterns of human groups. Because body parts may be transported for specific products such as meat, marrow or grease, a pattern that usually attracts attention in many archaeological sites is the low proportions of appendicular epiphyses. Here we present the case of faunal assemblages from the lower stratigraphic sequence of Qesem Cave, Israel, dated to ca. 430 to 300 ka. All bone accumulations are characterized by a biased skeletal profile including mainly long-limb bones and a virtual absence of epiphyses. The assemblages also show density-mediated attrition not linked to fossil-diagenetic processes, a targeted specific destruction to the most greasy articular ends and an almost total absence of carnivore intervention. Our goal here is to explore the processes that entail the destruction of appendicular epiphyses at Qesem Cave, as well as propose viable hypotheses to explain their underrepresentation on-site. Our results shed light on the domestic activities linked to the processing of bones at the site and support the importance of animal grease in the caloric intake of Middle Pleistocene humans.
Across the last ~50,000 years (the late Quaternary) terrestrial vertebrate faunas have experienced severe losses of large species (megafauna), with most extinctions occurring in the Late Pleistocene and Early to Middle Holocene. Debate on the causes has been ongoing for over 200 years, intensifying from the 1960s onward. Here, we outline criteria that any causal hypothesis needs to account for. Importantly, this extinction event is unique relative to other Cenozoic (the last 66 million years) extinctions in its strong size bias. For example, only 11 out of 57 species of megaherbivores (body mass ≥1,000 kg) survived to the present. In addition to mammalian megafauna, certain other groups also experienced substantial extinctions, mainly large non-mammalian vertebrates and smaller but megafauna-associated taxa. Further, extinction severity and dates varied among continents, but severely affected all biomes, from the Arctic to the tropics. We synthesise the evidence for and against climatic or modern human (Homo sapiens) causation, the only existing tenable hypotheses. Our review shows that there is little support for any major influence of climate, neither in global extinction patterns nor in fine-scale spatiotemporal and mechanistic evidence. Conversely, there is strong and increasing support for human pressures as the key driver of these extinctions, with emerging evidence for an initial onset linked to pre-sapiens hominins prior to the Late Pleistocene. Subsequently, we synthesize the evidence for ecosystem consequences of megafauna extinctions and discuss the implications for conservation and restoration. A broad range of evidence indicates that the megafauna extinctions have elicited profound changes to ecosystem structure and functioning. The late-Quaternary megafauna extinctions thereby represent an early, large-scale human-driven environmental transformation, constituting a progenitor of the Anthropocene, where humans are now a major player in planetary functioning. Finally, we conclude that megafauna restoration via trophic rewilding can be expected to have positive effects on biodiversity across varied Anthropocene settings.
This paper examines the hypothesis that changes in hunting weapons during the Paleolithic were a direct response to a progressive decline in prey size. The study builds upon a unified hypothesis that explains Paleolithic human evolutionary and behavioral/cultural phenomena, including improved cognitive capabilities, as adaptations to mitigate declined energetic returns due to a decline in prey size. Five selected case studies in Africa and Europe were analyzed to test this hypothesis, focusing on the relative presence of megaherbivores (>1000 kg) in the transition between the Acheulean/Early Stone Age and the Middle Paleolithic/Middle Stone Age. The findings indicate a decline in megaherbivores’ presence and biomass contribution in the studied transition period associated with the introduction of Levallois technology. We review the evolution of hunting weapons, including wooden-tipped and stone-tipped spears and bows and arrows. Analysis of tip size and breakage patterns indicate a reduction in point size over time, aligning with the declining prey size. We propose that changes in hunting weapons and strategies were driven by the practical and ontological incentives presented by the availability and size of prey. Developing smaller, more precise weapons required increased cognitive capacities, leading to the parallel evolution of human cognitive abilities.
Enlarging brains have been held up as the classic (if not the only) example of a consistent long-term trend in human evolution. And hominin endocranial volumes certainly expanded four-fold over the subfamily’s seven-million-year history, while on a very coarse scale later hominids showed a strong tendency to have larger brains than earlier ones. However, closer scrutiny of this apparent trend reveals that it was extremely episodic and irregular, a fact that argues against the notion that it was driven by social interactions internal to the hominin clade. In addition, an overall tendency to brain volume increase was expressed independently and concurrently within at least three separate lineages of the genus Homo – suggesting that, whatever the exact influences were that promoted this global trend, they need to be sought among stimuli that acted comprehensively over the entire vast range of periods, geographies and environments that members of our subfamily occupied. Significantly, though, the dramatic recent shrinkage of the brain within the species Homo sapiens implies that the emergence of modern human cognition (via the adoption of the symbolic information processing mode, likely driven by the spontaneous invention of language in an exaptively enabled brain) was not the culmination of the overall hominin trend towards brain enlargement, but rather a departure from it.
The oldest Oldowan tool sites, from around 2.6 million years ago, have previously been confined to Ethiopia's Afar Triangle. We describe sites at Nyayanga, Kenya, dated to 3.032 to 2.581 million years ago and expand this distribution by over 1300 kilometers. Furthermore, we found two hippopotamid butchery sites associated with mosaic vegetation and a C4 grazer-dominated fauna. Tool flaking proficiency was comparable with that of younger Oldowan assemblages, but pounding activities were more common. Tool use-wear and bone damage indicate plant and animal tissue processing. Paranthropus sp. teeth, the first from southwestern Kenya, possessed carbon isotopic values indicative of a diet rich in C4 foods. We argue that the earliest Oldowan was more widespread than previously known, used to process diverse foods including megafauna, and associated with Paranthropus from its onset.
The Early Pleistocene (2.58-0.78 Ma) was a period of major evolutionary changes in the hominin lineage. The progressive consolidation of bipedal locomotion, alongside increases in cranial capacity and behavioural flexibility, allowed early Homo to exploit an increasing diversity of resources and environmental settings within the changing landscapes of East Africa and beyond. These complex processes were not necessarily linear or spatially uniform, given the technological diversity documented, particularly during the Oldowan-Acheulean transition. In this paper, we argue that human populations experienced a considerable demographic expansion from c.1.7-1.5 Ma onwards, expressed in the number, size, density, and distribution of archaeological sites. These patterns resulted from the interplay of high-yielding animal resource exploitation strategies, technological investment, prosocial behaviours as well as increasingly structured land use patterns. A more consolidated hominin demographic structure led to the extinction of large sympatric carnivore species, while larger group sizes would have led to more successful Out-of-Africa dispersals.
Understanding the evolutionary consequences of wildlife exploitation is increasingly important as harvesting becomes more efficient. We examined the impacts of ivory poaching during the Mozambican Civil War (1977 to 1992) on the evolution of African savanna elephants (Loxodonta africana) in Gorongosa National Park. Poaching resulted in strong selection that favored tusklessness amid a rapid population decline. Survey data revealed tusk-inheritance patterns consistent with an X chromosome–linked dominant, male-lethal trait. Whole-genome scans implicated two candidate genes with known roles in mammalian tooth development (AMELX and MEP1a), including the formation of enamel, dentin, cementum, and the periodontium. One of these loci (AMELX) is associated with an X-linked dominant, male-lethal syndrome in humans that diminishes the growth of maxillary lateral incisors (homologous to elephant tusks). This study provides evidence for rapid, poaching-mediated selection for the loss of a prominent anatomical trait in a keystone species.
Evolutionary explanations are not only common in the biological sciences, but also widespread outside biology. But an account of how evolutionary explanations perform their explanatory work is still lacking. This paper develops such an account. I argue that available accounts of explanations in evolutionary science miss important parts of the role of history in evolutionary explanations. I argue that the historical part of evolutionary science should be taken as having genuine explanatory force, and that it provides how-possibly explanations sensu Dray. I propose an account of evolutionary explanations as comparative-composite explanations consisting of two distinct kinds of explanations, one processual and one historical, that are connected via the explanandum's evolvability to show how the explanandum is the product of its evolutionary past. The account is both a reconstruction of how evolutionary explanations in biology work and a guideline specifying what kind of explanations evolutionary research programs should develop.
The human trophic level (HTL) during the Pleistocene and its degree of variability serve, explicitly or tacitly, as the basis of many explanations for human evolution, behavior, and culture. Previous attempts to reconstruct the HTL have relied heavily on an analogy with recent hunter‐gatherer groups' diets. In addition to technological differences, recent findings of substantial ecological differences between the Pleistocene and the Anthropocene cast doubt regarding that analogy's validity. Surprisingly little systematic evolution‐guided evidence served to reconstruct HTL. Here, we reconstruct the HTL during the Pleistocene by reviewing evidence for the impact of the HTL on the biological, ecological, and behavioral systems derived from various existing studies. We adapt a paleobiological and paleoecological approach, including evidence from human physiology and genetics, archaeology, paleontology, and zoology, and identified 25 sources of evidence in total. The evidence shows that the trophic level of the Homo lineage that most probably led to modern humans evolved from a low base to a high, carnivorous position during the Pleistocene, beginning with Homo habilis and peaking in Homo erectus. A reversal of that trend appears in the Upper Paleolithic, strengthening in the Mesolithic/Epipaleolithic and Neolithic, and culminating with the advent of agriculture. We conclude that it is possible to reach a credible reconstruction of the HTL without relying on a simple analogy with recent hunter‐gatherers' diets. The memory of an adaptation to a trophic level that is embedded in modern humans' biology in the form of genetics, metabolism, and morphology is a fruitful line of investigation of past HTLs, whose potential we have only started to explore.
We hypothesize that megafauna extinctions throughout the Pleistocene, that led to a progressive decline in large prey availability, were a primary selecting agent in key evolutionary and cultural changes in human prehistory. The Pleistocene human past is characterized by a series of transformations that include the evolution of new physiological traits and the adoption, assimilation, and replacement of cultural and behavioral patterns. Some changes, such as brain expansion, use of fire, developments in stone-tool technologies, or the scale of resource intensification, were uncharacteristically progressive. We previously hypothesized that humans specialized in acquiring large prey because of their higher foraging efficiency, high biomass density, higher fat content, and the use of less complex tools for their acquisition. Here, we argue that the need to mitigate the additional energetic cost of acquiring progressively smaller prey may have been an ecological selecting agent in fundamental adaptive modes demonstrated in the Paleolithic archaeological record. We describe several potential associations between prey size decline and specific evolutionary and cultural changes that might have been driven by the need to adapt to increased energetic demands while hunting and processing smaller and smaller game.
Hunter-gatherers, especially Pleistocene examples, are not well-represented in archeological studies of niche construction. However, as the role of humans in shaping environments over long time scales becomes increasingly apparent, it is critical to develop archeological proxies and testable hypotheses about early hunter-gatherer impacts. Modern foragers engage in niche constructive behaviors aimed at maintaining or increasing the productivity of their environments, and these may have had significant ecological consequences over later human evolution. In some cases, they may also represent behaviors unique to modern Homo sapiens. Archeological and paleoenvironmental data show that African hunter-gatherers were niche con-structors in diverse environments, which have legacies in how ecosystems function today. These can be conceptualized as behaviorally mediated trophic cascades, and tested using archeological and paleoenvironmental proxies. Thus, large-scale niche construction behavior is possible to identify at deeper time scales, and may be key to understanding the emergence of modern humans. K E Y W O R D S burning, environmental impacts, foragers, middle stone age, modern human, Pleistocene
Although climate change is considered to have been a large-scale driver of African human evolution, landscape scale shifts in ecological resources that may have shaped novel hominin adaptations are rarely investigated. We use well-dated, high-resolution, drill-core datasets to understand ecological dynamics associated with a major adaptive transition in the archeological record ~24 km from the coring site. Outcrops preserve evidence of the replacement of Acheulean by Middle Stone Age (MSA) technological, cognitive, and social innovations between 500 and 300 thousand years (ka) ago, contemporaneous with large-scale taxonomic and adaptive turnover in mammal herbivores. Beginning ~400 ka ago, tectonic, hydrological, and ecological changes combined to disrupt a relatively stable resource base, prompting fluctuations of increasing magnitude in freshwater availability, grassland communities, and woody plant cover. Interaction of these factors offers a resource-oriented hypothesis for the evolutionary success of MSA adaptations, which likely contributed to the ecological flexibility typical of Homo sapiens foragers.
While the anthropogenic impact on ecosystems today is evident, it remains unclear if the detrimental effect of hominins on co‐occurring biodiversity is a recent phenomenon or has also been the pattern for earlier hominin species. We test this using the East African carnivore fossil record. We analyse the diversity of carnivores over the last four million years and investigate whether any decline is related to an increase in hominin cognitive capacity, vegetation changes or climatic changes. We find that extinction rates in large carnivores correlate with increased hominin brain size and with vegetation changes, but not with precipitation or temperature changes. While temporal analyses cannot distinguish between the effects of vegetation changes and hominins, we show through spatial analyses of contemporary carnivores in Africa that only hominin causation is plausible. Our results suggest that substantial anthropogenic influence on biodiversity started millions of years earlier than currently assumed. While the anthropogenic impact on ecosystems today is evident, it remains unclear if the detrimental effect of the human lineage on co‐occurring biodiversity is a recent phenomenon or has also been the pattern for earlier hominin species. Focusing on fossil data from East Africa, the cradle of mankind, we find support for a strong negative effect on co‐occurring biodiversity caused by our ancestors already in the Pliocene. Our results suggest that substantial anthropogenic influence on biodiversity started millions of years earlier than currently assumed.
Bone marrow and grease constitute an important source of nutrition and have attracted the attention of human groups since prehistoric times. Marrow consumption has been linked to immediate consumption following the procurement and removal of soft tissues. Here, we present the earliest evidence for storage and delayed consumption of bone marrow at Qesem Cave, Israel (~420 to 200 ka). By using experimental series controlling exposure time and environmental parameters, combined with chemical analyses, we evaluated bone marrow preservation. The combination of archaeological and experimental results allowed us to isolate specific marks linked to dry skin removal and determine a low rate of marrow fat degradation of up to 9 weeks of exposure. This is the earliest evidence of such previously unidentified behavior, and it offers insights into the socio-economy of the human groups who lived at Qesem and may mark a threshold to new modes of Palaeolithic human adaptation.
It has been argued that men's hunting in many forager groups is not, primarily, a means of family provisioning but is a costly way of signaling otherwise cryptic qualities related to hunting ability. Much literature concerning the signaling value of hunting draws links to Zahavi's handicap principle and the costly signaling literature in zoology. However, although nominally grounded in the same theoretical paradigm, these literatures have evolved separately. Here I review honest signaling theory in both hunter‐gatherer studies and zoology and highlight three issues with the costly signaling literature in hunger‐gather studies: (a) an overemphasis on the demonstration of realized costs, which are neither necessary nor sufficient to diagnose costly signaling; (b) a lack of clear predictions about what specific qualities hunting actually signals; and (c) an insufficient focus on the broadcast effectiveness of hunting and its value as a heuristics for signal recipients. Rather than signaling hunting prowess, hunting might instead facilitate reputation‐building.
Many of the world's vertebrates have experienced large population and geographic range declines due to anthropogenic threats that put them at risk of extinction. The largest vertebrates, defined as megafauna, are especially vulnerable. We analyzed how human activities are impacting the conservation status of megafauna within six classes: mammals, ray-finned fish, cartilaginous fish, amphibians, birds, and reptiles. We identified a total of 362 extant megafauna species. We found that 70% of megafauna species with sufficient information are decreasing and 59% are threatened with extinction. Surprisingly, direct harvesting of megafauna for human consumption of meat or body parts is the largest individual threat to each of the classes examined , and a threat for 98% (159/162) of threatened species with threat data available. Therefore, minimizing the direct killing of the world's largest vertebrates is a priority conservation strategy that might save many of these iconic species and the functions and services they provide.
Aim
Vertebrates are declining worldwide, yet a comprehensive examination of the sources of mortality is lacking. We conducted a global synthesis of terrestrial vertebrate cause‐specific mortality to compare the sources of mortality across taxa and determine predictors of susceptibility to these sources of mortality.
Location
Worldwide.
Time period
1970–2018.
Major taxa studied
Mammals, birds, reptiles and amphibians.
Methods
We searched for studies that used telemetry to determine the cause of death of terrestrial vertebrates. We determined whether each mortality was caused by anthropogenic or natural sources and further classified mortalities within these two categories (e.g. harvest, vehicle collision and predation). For each study, we determined the diet and average adult body mass of the species and whether the study site permitted hunting. Mortalities were separated into juvenile or adult age classes. We used linear mixed effects models to predict the percentage of mortality from each source and the overall magnitude of mortality based on these variables.
Results
We documented 42,755 mortalities of known cause from 120,657 individuals representing 305 vertebrate species in 1,114 studies. Overall, 28% of mortalities were directly caused by humans and 72% from natural sources. Predation (55%) and legal harvest (17%) were the leading sources of mortality.
Main conclusions
Humans were directly responsible for more than one‐quarter of global terrestrial vertebrate mortality. Larger birds and mammals were harvested more often and suffered increased anthropogenic mortality. Anthropogenic mortality of mammals and birds outside areas that prohibited hunting was higher than within areas where hunting was permitted. Mammals experienced shifts from predominately natural to anthropogenic mortality as they matured. Humans are a major contributor to terrestrial vertebrate mortality, potentially impacting evolutionary processes and ecosystem functioning.
Background
Humans and other primates have evolved particular morphological and biological traits (e.g., larger brains, slower growth, longer-lived offspring) that distinguish them from most other mammals. The evolution of many distinctive human characteristics, such as our large brain sizes, reduced gut sizes, and high activity budgets, suggest major energetic and dietary shifts.
Main body
Over the course of the last three million years, hominin brain sizes tripled. It is often taken for granted that the benefit of a larger brain is an increase in “intelligence” that makes us stand out among other mammals, including our nearest relatives, the primates. In the case of humans, brain expansion was associated with changes in diet, foraging, and energy metabolism. The first marked expansion occurred with the appearance of the genus Homo . Improved diet quality, allomaternal subsidies, cognitive buffering [by earlier weaning and longer juvenile periods], reduced costs for locomotion and by cooperative behavior, and reduced allocation to production, all operated simultaneously, thus enabling the extraordinary brain enlargement in our lineage.
Conclusion
It appears that major expansion of brain size in the human lineage is the product of synergistically interacting dietary/nutritional and social forces. Although dietary change was not being the sole force responsible for the evolution of large brain size, the exploitation of high-quality foods likely fueled the energetic costs of larger brains and necessitated more complex behaviors that would have selected for greater brain size.
Marathousa 1 is a Lower Palaeolithic open-air site located in the Megalopolis basin, an area in Southern Greece known for its fossiliferous sediments. Mining activities in the basin uncovered a thick sequence of Middle Pleistocene lacustrine deposits representing the environment of a palaeolake. Marathousa 1 was discovered in 2013 during a targeted palaeoanthropological survey and excavated subsequently by an interdisciplinary team from the Ephoreia of Palaeoanthropology–Speleology of Greece and the University of Tübingen, Germany. This article presents results from the ongoing investigation and reviews the state of knowledge about the site. Systematic excavations during five field seasons have exposed a total of 72 m² and revealed a partial skeleton of the elephant Palaeoloxodon antiquus and remains of other large mammals in spatial and stratigraphic association with a “small tool” lithic assemblage. Faunal and taphonomic studies indicate the presence of cut-marks and percussion damage on elephant and other large mammal bones. The study of site formation processes, together with taphonomic and geostatistic spatial analyses confirm the association of fossil and hominin activity remains and the stratigraphic integrity of the site. Radiometric dating, geological and biostratigraphical evidence suggest that hominin activity at the site occurred between 0.5 and 0.4 Ma. Marathousa 1 is the oldest currently known archaeological site in Greece and the only Lower Palaeolithic butchering site in the Southern Balkans. It is also a key site for documenting high resolution palaeoclimatic, palaeoenvironmental and cultural records of a geographical area that potentially acted as a refugium during the successive waves of hominin colonization of Europe.
The human brain is unusually large. It has tripled in size from Australopithecines to modern humans¹ and has become almost six times larger than expected for a placental mammal of human size². Brains incur high metabolic costs³ and accordingly a long-standing question is why the large human brain has evolved⁴. The leading hypotheses propose benefits of improved cognition for overcoming ecological⁵⁻⁷, social⁸⁻¹⁰ or cultural¹¹⁻¹⁴ challenges. However, these hypotheses are typically assessed using correlative analyses, and establishing causes for brain-size evolution remains difficult15,16. Here we introduce a metabolic approach that enables causal assessment of social hypotheses for brain-size evolution. Our approach yields quantitative predictions for brain and body size from formalized social hypotheses given empirical estimates of the metabolic costs of the brain. Our model predicts the evolution of adult Homo sapiens-sized brains and bodies when individuals face a combination of 60% ecological, 30% cooperative and 10% between-group competitive challenges, and suggests that between-individual competition has been unimportant for driving human brain-size evolution. Moreover, our model indicates that brain expansion in Homo was driven by ecological rather than social challenges, and was perhaps strongly promoted by culture. Our metabolic approach thus enables causal assessments that refine, refute and unify hypotheses of brain-size evolution.
Megafaunal loss
Today, it is well known that human activities put larger animals at greater risk of extinction. Such targeting of the largest species is not new, however. Smith et al. show that biased loss of large-bodied mammal species from ecosystems is a signature of human impacts that has been following hominin migrations since the Pleistocene. If the current trend continues, terrestrial mammal body sizes will become smaller than they have been over the past 45 million years. Megafaunal mammals have a major impact on the structure of ecosystems, so their loss could be particularly damaging.
Science , this issue p. 310
Comparative studies have identified a wide range of behavioural and ecological correlates of relative brain size, with results differing between taxonomic groups, and even within them. In primates for example, recent studies contradict one another over whether social or ecological factors are critical. A basic assumption of such studies is that with sufficiently large samples and appropriate analysis, robust correlations indicative of selection pressures on cognition will emerge. We carried out a comprehensive re-examination of correlates of primate brain size using two large comparative datasets and phylogenetic comparative methods. We found evidence in both datasets for associations between brain size and ecological variables (home range size, diet and activity period), but little evidence for an effect of social group size, a correlation which has previously formed the empirical basis of the Social Brain Hypothesis. However, reflecting divergent results in the literature, our results exhibited instability across datasets, even when they were matched for species composition and predictor variables. We identify several potential empirical and theoretical difficulties underlying this instability and suggest that these issues raise doubts about inferring cognitive selection pressures from behavioural correlates of brain size. © 2017 The Author(s) Published by the Royal Society. All rights reserved.
The social brain hypothesis posits that social complexity is the primary driver of primate cognitive complexity, and that social pressures ultimately led to the evolution of the large human brain. Although this idea has been supported by studies indicating positive relationships between relative brain and/or neocortex size and group size, reported effects of different social and mating systems are highly conflicting. Here, we use a much larger sample of primates, more recent phylogenies, and updated statistical techniques, to show that brain size is predicted by diet, rather than multiple measures of sociality, after controlling for body size and phylogeny. Specifically, frugivores exhibit larger brains than folivores. Our results call into question the current emphasis on social rather than ecological explanations for the evolution of large brains in primates and evoke a range of ecological and developmental hypotheses centred on frugivory, including spatial information storage, extractive foraging and overcoming metabolic constraints.
The exhibition of increasingly intensive and complex niche construction behaviors through time is a key
feature of human evolution, culminating in the advanced capacity for ecosystem engineering exhibited by
Homo sapiens. A crucial outcome of such behaviors has been the dramatic reshaping of the global biosphere,
a transformation whose early origins are increasingly apparent from cumulative archaeological and
paleoecological datasets. Such data suggest that, by the Late Pleistocene, humans had begun to engage in
activities that have led to alterations in the distributions of a vast array of species across most, if not all,
taxonomic groups. Changes to biodiversity have included extinctions, extirpations, and shifts in species
composition, diversity, and community structure. We outline key examples of these changes, highlighting
findings from the study of new datasets, like ancient DNA (aDNA), stable isotopes, and microfossils, as
well as the application of new statistical and computational methods to datasets that have accumulated
significantly in recent decades. We focus on four major phases that witnessed broad anthropogenic
alterations to biodiversity—the Late Pleistocene global human expansion, the Neolithic spread of agriculture,
the era of island colonization, and the emergence of early urbanized societies and commercial networks.
Archaeological evidence documents millennia of anthropogenic transformations that have created
novel ecosystems around the world. This record has implications for ecological and evolutionary research,
conservation strategies, and the maintenance of ecosystem services, pointing to a significant need for
broader cross-disciplinary engagement between archaeology and the biological and environmental sciences.
This chapter examines the evidence for diet amongst Middle Palaeolithic foragers in Europe and southwest Asia from c. 300,000 to 40,000 years ago, concentrating on faunal and isotopic approaches. Published faunal evidence shows that Middle Palaeolithic hominins in both regions hunted a relatively narrow range of medium-to large-sized ungulates, with occasional exploitation of megaherbivores more evident in open sites than in caves and rockshelters. Broader diets have been documented in southern Europe, although regular consumption of fast, small-sized taxa emerged only later during the Upper Palaeolithic. Stable light isotope data, often interpreted as indicating that European Neanderthals were top-level predators preferring either megaherbivores, or bovids and horses, only partly accords with the faunal evidence. Taphonomic considerations suggest that energy procurement, especially as fat, and the effects of transport constraints have so far not been sufficiently considered when assessing the dietary composition of Middle Palaeolithic hominins.
Humans are limited in their capacity to convert protein into energy. We present a hypothesis that a “bell” shaped thorax and a wide pelvis evolved in Neandertals, at least in part, as an adaptation to a high protein diet. A high protein diet created a need to house an enlarged liver and urinary system in a wider lower trunk. To test the hypothesis, we applied a model developed to identify points of nutritional stress. A ratio of obligatory dietary fat to total animal fat and protein sourced calories is calculated based on various known and estimated parameters. Stress is identified when the obligatory dietary fat ratio is higher than fat content ratios in available prey. The model predicts that during glacial winters, when carbohydrates weren't available, 74%−85% of Neandertals' caloric intake would have had to come from animal fat. Large animals contain around 50% fat calories, and their fat content is diminished during winter, so a significant stressful dietary fat deficit was identified by the model. This deficit could potentially be ameliorated by an increased capability to convert protein into energy. Given that high protein consumption is associated with larger liver and kidneys in animal models, it appears likely that the enlarged inferior section of the Neandertals thorax and possibly, in part, also his wide pelvis, represented an adaptation to provide encasement for those enlarged organs. Behavioral and evolutionary implications of the hypothesis are also discussed. Am J Phys Anthropol, 2016.
Abstract
Background and objectives: Recommendations to limit the dietary consumption of saturated fat have been
adopted by public health organizations in most countries. However, recent scientific studies and reviews have
questioned the alleged negative health claims regarding saturated fat.
This research aims to provide a historical, evolutionary point of view to the debate through a short review of
evidence for animal fat consumption by Paleolithic and recent traditional societies, and the discernment of
how recent traditional societies perceived animal fat in terms of health and other lifestyle aspects.
Methodology: Literature review of the importance of animal fat's dietary consumption in prehistoric and
recent traditional societies and scanning of ethnographic records for symbolic use of animal fat in rituals,
linguistics and mythology. The contexts of such cultural expressions provide us with the peoples' perception
of the analogues quality that animal fat imparts in its use as a symbol.
Results: Collection of 200 cases from culturally and geographically diverse traditional societies, reveals that in
all three expression forms, there appears to be a clear tendency to associate animal fat with extremely positive
meanings like "fertility", "sacredness", "wealth", "health", and even " a source of creation" and life itself.
Conclusion: In line with evidence for the importance of dietary animal fat in prehistoric and traditional
societies, the studied traditional societies perceived animal fat as a vital component of their diet and a
profound source of health rather than an impediment to health as it is presented in many dietary
recommendations today.
Neanderthals hunted and butchered straight-tusked elephants, the largest terrestrial mammals of the Pleistocene, in a lake landscape on the North European plain, 125,000 years ago, as recently shown by a study of the Last Interglacial elephant assemblage from Neumark-Nord (Germany). With evidence for a remarkable focus on adult males and on their extended utilization, the data from this location are thus far without parallel in the archaeological record. Given their relevance for our knowledge of the Neanderthal niche, we investigated whether the Neumark-Nord subsistence practices were more than a local phenomenon, possibly determined by local characteristics. Analyzing elephant remains from two other Last Interglacial archaeological sites on the North European plain, Gröbern and Taubach, we identified in both assemblages similar butchering patterns as at Neumark-Nord, demonstrating that extended elephant exploitation was a widespread Neanderthal practice during the (early part of the) Last Interglacial. The substantial efforts needed to process these animals, weighing up to 13 metric tons, and the large amounts of food generated suggest that Neanderthals either had ways of storing vast amounts of meat and fat and/or temporarily aggregated in larger groups than commonly acknowledged. The data do not allow us to rule out one of the two explanations, and furthermore both factors, short-term larger group sizes as well as some form of food preservation, may have played a role. What the data do show is that exploitation of large straight-tusked elephants was a widespread and recurring phenomenon amongst Last Interglacial Neanderthals on the North European plain.
The Earth has lost approximately half of its large mammal species (≥45 kg, one-third of species ≥9 kg) over the past 120,000 years, resulting in depauperate megafauna communities worldwide. Despite substantial interest and debate for over a century, the reasons for these exceptionally high extinction rates and major transformation of the biosphere remain contested. The predominant explanations are climate change, hunting by modern humans (Homo sapiens), or a combination of both. To evaluate the evidence for each hypothesis, statistical models were constructed to test the predictive power of prehistoric human and hominin presence and migration on megafauna extinction severity and on extinction bias toward larger species. Models with anthropic predictors were compared to models that considered late-Quaternary (120–0 kya) climate change and it was found that models including human factors outperformed all purely climatic models. These results thus support an overriding impact of Homo sapiens on megafauna extinctions. Given the disproportionate impact of large-bodied animals on vegetation structure, plant dispersal, nutrient cycling and co-dependent biota, this simplification and downsizing of mammal faunas worldwide represents the first planetary-scale, human-driven transformation of the environment.
Significance
We have developed an Africa-wide synthesis of paleoenvironmental variability over the Plio-Pleistocene. We show that there is strong evidence for orbital forcing of variability during this time that is superimposed on a longer trend of increasing environmental variability, supporting a combination of both low- and high-latitude drivers of variability. We combine these results with robust estimates of mammalian speciation and extinction rates and find that variability is not significantly correlated with these rates. These findings do not currently support a link between environmental variability and turnover and thus fail to corroborate predictions derived from the variability selection hypothesis.
Over the last half century, anthropologists have vigorously debated the adaptive motivations underlying food acquisition choices and food-sharing among hunter-gatherer groups. Numerous explanations have been proposed to account for high-levels of generosity in food-sharing, including self- and family-provisioning, reciprocity, tolerated theft and pro-social- or skill-signaling. However, few studies have asked foragers directly and systematically about the motivations underlying their foraging and sharing decisions. We recruited 110 Hadza participants and employed a combination of free-response, yes/no, ranking and forced-choice questions to do just this. In free-response answers, respondents typically gave outcome-oriented accounts of foraging motive (e.g., to get food) and moralistic accounts of sharing motive (e.g., I have a good heart). In ranking tasks, participants gave precedence to reciprocity as a motive for sharing food beyond the household. We found small but clear gender differences in foraging motive, in line with previous predictions: women were more likely than men to rank family-provisioning highly whereas men were more likely than women to rank skill-signaling highly. However, despite these gender differences, the relative importance of different motivations was similar across genders and skill-signaling, sharing and family-provisioning were the most important motivators of foraging activity for both men and women. Contrary to the expectations of tolerated theft, peer complaints and requests for food ranked very low. There are several compelling reasons that evolutionary thinkers, typically interested in ultimate-level adaptive processes, have traditionally eschewed direct and explicit investigations of motive. However, these data may yet provide important insights.
Multiple large-bodied species went extinct during the Pleistocene. Changing climates and/or human hunting are the main hypotheses used to explain these extinctions. We studied the causes of Pleistocene extinctions in the Southern Levant, and their subsequent effect on local hominin food spectra, by examining faunal remains in archaeological sites across the last 1.5 million years. We examined whether climate and climate changes, and/or human cultures, are associated with these declines. We recorded animal abundances published in the literature from 133 stratigraphic layers, across 58 Pleistocene and Early Holocene archaeological sites, in the Southern Levant. We used linear regressions and mixed models to assess the weighted mean mass of faunal assemblages through time and whether it was associated with temperature, paleorainfall, or paleoenvironment (C3 vs. C4 vegetation). We found that weighted mean body mass declined log-linearly through time. Mean hunted animal masses 10,500 years ago, were only 1.7% of those 1.5 million years ago. Neither body size at any period, nor size change from one layer to the next, were related to global temperature or to temperature changes. Throughout the Pleistocene, new human lineages hunted significantly smaller prey than the preceding ones. This suggests that humans extirpated megafauna throughout the Pleistocene, and when the largest species were depleted the next-largest were targeted. Technological advancements likely enabled subsequent human lineages to effectively hunt smaller prey replacing larger species that were hunted to extinction or until they became exceedingly rare.
Estimates of the human trophic level and dietary quality during the Paleolithic are the basis for many hypotheses and interpretations regarding human evolution and behavior. We describe an additional factor that could have significantly influenced human evolution and behavior, the availability of large prey animals.
Given the importance of large prey and the mounting evidence of the decline in its abundance throughout the Pleistocene, we question the reliability of past reconstructions of the human trophic level that were heavily based on analogies with the recent ethnographic record.
We review the ecological and technological records of the Hadza and the Ju/’hoansi (!Kung), two recent hunter-gatherers' groups that dominate the literature as acceptable ethnographic analogs for Paleolithic Africa. We find that their dietary record reflects, as expected by our model, an adaptation to an ecological reality of increased vegetal biomass and reduced large prey biomass that differ substantially from the ecology of most of the Pleistocene but do share analogical trends with the late Upper Paleolithic when the Late Quaternary Megafauna Extinction took place.
A growing body of literature proposes that our ancestors contributed to large mammal extinctions in Africa long before the appearance of Homo sapiens, with some arguing that premodern hominins (e.g., Homo erectus) triggered the demise of Afri-ca's largest herbivores and the loss of carnivoran diversity. Though such arguments have been around for decades, they are now increasingly accepted by those concerned with biodiversity decline in the present-day, despite the near complete absence of critical discussion or debate. To facilitate that process, here we review ancient anthropogenic extinction hypotheses and critically examine the data underpinning them. Broadly speaking, we show that arguments made in favor of ancient anthro-pogenic extinctions are based on problematic data analysis and interpretation, and are substantially weakened when extinctions are considered in the context of long-term evolutionary, ecological, and environmental changes. Thus, at present, there is no compelling empirical evidence supporting a deep history of hominin impacts on Africa's faunal diversity.
The transition of hominins to a largely meat-based diet ∼1.8 million years ago led to the exploitation of other mammals for food and resources. As hominins, particularly archaic and modern humans, became increasingly abundant and dispersed across the globe, a temporally and spatially transgressive extinction of large-bodied mammals followed; the degree of selectivity was unprecedented in the Cenozoic fossil record. Today, most remaining large-bodied mammal species are confined to Africa, where they co-evolved with hominins. Here, using a comprehensive global dataset of mammal distribution, life history and ecology, we examine the consequences of ‘body size downgrading’ of mammals over the late Quaternary on fundamental macroecological patterns. Specifically, we examine changes in species diversity, global and continental body size distributions, allometric scaling of geographic range size with body mass, and the scaling of maximum body size with area. Moreover, we project these patterns toward a potential future scenario in which all mammals currently listed as vulnerable on the IUCN's Red List are extirpated. Our analysis demonstrates that anthropogenic impact on earth systems predates the terminal Pleistocene and has grown as populations increased and humans have become more widespread. Moreover, owing to the disproportionate influence on ecosystem structure and function of megafauna, past and present body size downgrading has reshaped Earth's biosphere. Thus, macroecological studies based only on modern species yield distorted results, which are not representative of the patterns present for most of mammal evolution. Our review supports the concept of benchmarking the ‘Anthropocene’ with the earliest activities of Homo sapiens.
The habitual consumption of large-animal resources (e.g., similar sized or larger than the consumer) separates human
and nonhuman primate behavior. Flaked stone tool use, another important hominin behavior, is often portrayed as
being functionally related to this by the necessity of a sharp edge for cutting animal tissue. However, most research on
both issues emphasizes sites that postdate ca. 2.0 million years ago. This paper critically examines the theoretical significance of the earlier origins of these two behaviors, their proposed interrelationship, and the nature of the empirical record. We argue that concepts of meat-eating and tool use are too loosely defined: outside-bone nutrients (e.g., meat) and inside-bone nutrients (e.g., marrow and brains) have different macronutrient characteristics (protein vs. fat), mechanical requirements for access (cutting vs. percussion), search, handling and competitive costs, encounter rates, and net returns. Thus, they would have demanded distinct technological and behavioral solutions. We propose that the
regular exploitation of large-animal resources—the “human predatory pattern”—began with an emphasis on percussion based scavenging of inside-bone nutrients, independent of the emergence of flaked stone tool use. This leads to a series of empirical test implications that differ from previous “meat-eating” origins scenarios.
Analysis of the Agate Basin component faunal remains from the Hell Gap Site (48G0305) Locality II suggests that the assemblage results from a multi-dimensional formational history. Comparisons of skeletal element frequencies with models of density-mediated attrition, bison settling velocities, and several nutritional utility indices indicate that both fluvial action and the transport of high marrow value elements from kill sites to the residential base in the Hell Gap Valley may have contributed to assemblage composition. Observations of impact related conchoidal flake scars document the intensive secondary processing of long bone elements. Although skeletal part frequencies likely document several taphonomic processes, when viewed together with bone modifications they suggest that the Agate Basin Paleoindians responsible for the Locality II deposits may have practiced a fat-seeking feeding strategy stressing the transport of high bulk protein/skeletal fat utility bison parts from kill sites to the residential base at Locality II.
What are the origins of intelligent behavior? The demands associated with living in complex social groups have been the favored explanation for the evolution of primate cognition in general and human cognition in particular. However, recent comparative research indicates that ecological variation can also shape cognitive abilities. I synthesize the emerging evidence that ‘foraging cognition’ – skills used to exploit food resources, including spatial memory, decision-making, and inhibitory control – varies adaptively across primates. These findings provide a new framework for the evolution of human cognition, given our species’ dependence on costly, high-value food resources. Understanding the origins of the human mind will require an integrative theory accounting for how humans are unique in both our sociality and our ecology.
Many factors have been causally linked to the diversification of hunting during the European Palaeolithic: declining supplies of high-ranked prey, considerable human demographic growth, reduced residential mobility, larger populations of ubiquitous small mammals and significant technological developments. However, small prey exploitation was not uniform: the European rabbit (Oryctolagus cuniculus) is the most frequent species in the Upper Palaeolithic archaeological record of the Iberian Peninsula - south and Mediterranean area - and Southern France. This is demonstrated at Molí del Salt, an Upper Palaeolithic site located at Vimbodí (Catalonia, Spain), whose mammal fauna stands out for the predominance of rabbits [91% of minimum number of individuals (n=136)]. We analysed the faunal remains from one level [Asup (c. 12700-13000cal BP)] in order to identify the agent responsible for the faunal accumulation, and to reconstruct aspects of procurement and consumption that shed light on Palaeolithic subsistence strategies in the Northeast Iberian Peninsula. Our results indicate that human agency rather than carnivore activity was responsible for the bone accumulation at Molí del Salt. We identified all the stages in the consumption sequence from skinning to ingestion. We argue that the rabbits were mostly harvested during summer or winter or both seasons. Clearly, the European rabbit was a target species for the human groups which lived at Molí del Salt providing meat, and skin.
Recognising elements of a ‘modern’ mind or complex cognition in Stone Age archaeology is difficult and often disputed. A key question is whether, and in what way, the thinking of Homo sapiens differs from that of other species/sub-species of hominins. We argue that if the question of whether the modern mind is different from that of our ancestors or other members of the hominin family is to be fully explored, some focus should fall on technologies and behaviours unique to H. sapiens. Here we hypothesise about one such techno-behaviour: bow hunting. Other technologies and their associated behavioural repertoires, such as the heat treatment of rocks to improve knapping properties, and hunting with snares, represent similar opportunities to explore the cognition of early H. sapiens.
In a recent paper, Stiner reviewed certain trends in the Middle Palaeolithic (MP) economy and social behaviour, including most notably galvanization of the prime-age ungulate hunting niche, and the intensification of occupations in the form of domestic-residential camps. However, the emergence of these trends is blurred when we observe the European archaeological record before Marine Oxygen Isotope Stage 7. Our aim in this paper is to test the validity of some key arguments related to subsistence and occupation to assess the Lower Palaeolithic roots of these MP trends, using the faunal record of the TD10.1 bone bed level (ca. 300ka) at Gran Dolina (Atapuerca). The taphonomic results from this level indicate an assemblage composed almost exclusively of prime-age ungulates. Anthropogenic marks are very abundant, reflecting a wide variety of domestic activities. Early primary access to the carcasses by hominins, indicated by the taxonomic and mortality patterns, suggests the procurement of animal carcasses by regular hunting. Red deer, accompanied in lower proportions by other prey species, reinforce the selective character of the hominin subsistence strategies at the Gran Dolina TD10.1 bone bed, expanding temporally and geographically our documentation of the MP hominin predatory niche. Taphonomy, together with other results from technology and archaeo-stratigraphy, suggest that the bone bed accumulation reflects long-term hominin use of the site as a residential base camp, suggesting deep roots for the observed MP subsistence and occupational patterns.
Recent patterns of global change have highlighted the importance of understanding the dynamics and mechanisms of species range shifts and expansions. Unique demographic features, spatial processes, and selective pressures can result in the accumulation and evolution of distinctive phenotypic traits at the leading edges of expansions. We review the characteristics of expanding range margins and highlight possible mechanisms for the appearance of phenotypic differences between individuals at the leading edge and core of the range. The development of life history traits that increase dispersal or reproductive ability are predicted by theory and supported with extensive empirical evidence. Many examples of rapid phenotypic change are associated with trade-offs that may influence the persistence of the trait once expansion ends. Accounting for the effects of edge phenotypes and related trade-offs could be critical for predicting the spread of invasive species and population responses to climate change. This article is protected by copyright. All rights reserved.