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The appearance of Homo erectus shortly after 2.0 Ma is widely considered a turning point in human dietary evolution, with increased consumption of animal tissues driving the evolution of larger brain and body size and a reorganization of the gut. An increase in the size and number of zooarchaeological assemblages after the appearance of H. erectus is often offered as a central piece of archaeological evidence for increased carnivory in this species, but this characterization has yet to be subject to detailed scrutiny. Any widespread dietary shift leading to the acquisition of key traits in H. erectus should be persistent in the zooarchaeological record through time and can only be convincingly demonstrated by a broad-scale analysis that transcends individual sites or localities. Here, we present a quantitative synthesis of the zooarchaeological record of eastern Africa from 2.6 to 1.2 Ma. We show that several proxies for the prevalence of hominin carnivory are all strongly related to how well the fossil record has been sampled, which constrains the zooarchaeological visibility of hominin carnivory. When correcting for sampling effort, there is no sustained increase in the amount of evidence for hominin carnivory between 2.6 and 1.2 Ma. Our observations undercut evolutionary narratives linking anatomical and behavioral traits to increased meat consumption in H. erectus, suggesting that other factors are likely responsible for the appearance of its human-like traits.

Several hypotheses posit a link between the origin of Homo and climatic and environmental shifts between 3 and 2.5 Ma. Here we report on new results that shed light on the interplay between tectonics, basin migration and faunal change on the one hand and the fate of Australopithecus afarensis and the evolution of Homo on the other. Fieldwork at the new Mille-Logya site in the Afar, Ethiopia, dated to between 2.914 and 2.443 Ma, provides geological evidence for the northeast migration of the Hadar Basin, extending the record of this lacustrine basin to Mille-Logya. We have identified three new fossiliferous units, suggesting in situ faunal change within this interval. While the fauna in the older unit is comparable to that at Hadar and Dikika, the younger units contain species that indicate more open conditions along with remains of Homo . This suggests that Homo either emerged from Australopithecus during this interval or dispersed into the region as part of a fauna adapted to more open habitats. Key events in human evolution are thought to have occurred between 3 and 2.5 Ma, but the fossil record of this period is sparse. Here, Alemseged et al. report a new fossil site from this period, Mille-Logya, Ethiopia, and characterize the geology, basin evolution and fauna, including specimens of Homo .

Despite its clear functional role in hock (ankle) plantarflexion, the bovid calcaneus has been understudied with respect to the functional constraints imposed by locomotion in differing habitats, the allometric influence of inter-specific body size differences, and phylogenetic signal. This study uses a comparative sample of extant bovid species to shed light on the evolution of bovid calcaneal morphology. I measured eight linear measurements on 204 calcaneus specimens representing 41 extant bovid species. Using a morphological body size proxy validated against published species-mean body mass estimates, I performed Ordinary Least Squares regression to examine the allometric relationships of each measurement with body size. I classified each bovid species to a preferred habitat type based on published literature, and performed Phylogenetic Generalized Least Squares (PGLS) to test for differences in morphology between bovid taxa with different preferred habitats while considering evolutionary relatedness. I visualized morphological differences between taxa using Principal Components Analysis plotted in a phylomorphospace. Results demonstrate that several measurements of the bovid calcaneus have an allometric relationship to body size. The functional length of the calcaneus scales with negative allometry, which likely maintains a comparable safety factor within the calcaneal tuber at larger body sizes. While open-habitat bovids have relatively shorter calcaneal tubers, this difference is not significant when controlling for the influence of body size and phylogenetic signal using PGLS. Among bovid tribes that have a deep evolutionary history of adaptation to open habitats, Antilopini have relatively longer calcaneal tubers than Alcelaphini or Hippotragini, which may reflect the unique importance of stotting behavior in predator avoidance among antelopins. Overall, the morphology of the bovid calcaneus has been shaped by a complex interaction of phylogenetic and body-size constraints as well as adaptation to modes of predator avoidance mediated by preferred habitat.

Biotic homogenization—increasing similarity of species composition among ecological communities—has been linked to anthropogenic processes operating over the last century. Fossil evidence, however, suggests that humans have had impacts on ecosystems for millennia. We quantify biotic homogenization of North American mammalian assemblages during the late Pleistocene through Holocene (~30,000 ybp to recent), a timespan encompassing increased evidence of humans on the landscape (~20,000–14,000 ybp). From ~10,000 ybp to recent, assemblages became significantly more homogenous (>100% increase in Jaccard similarity), a pattern that cannot be explained by changes in fossil record sampling. Homogenization was most pronounced among mammals larger than 1 kg and occurred in two phases. The first followed the megafaunal extinction at ~10,000 ybp. The second, more rapid phase began during human population growth and early agricultural intensification (~2,000–1,000 ybp). We show that North American ecosystems were homogenizing for millennia, extending human impacts back ~10,000 years. Biotic homogenization, which is increased similarity in the composition of species among communities, is rising due to human activities. Using North American mammal fossil records from the past 30,000 years, this study shows that this phenomenon is ancient, beginning between 12,000 and 10,000 years ago with the extinction of the mammal megafauna.

Analysis of enamel stable carbon isotopes (δ 13 C enamel ) of fossil herbivores is an important tool for making inferences about Plio-Pleistocene vegetation structure in Africa and the environmental context of hominin evolution. Many palaeoecological studies implicitly or explicitly assume that individual variation in C 3 –C 4 plant consumption among fossil herbivores directly reflects the abundance of C 3 (trees, shrubs) or C 4 (low-altitude tropical grasses) vegetation. However, a strong link between δ 13 C enamel of herbivores and ecosystem vegetation structure has not been rigorously established. Here we combine δ 13 C enamel data from a large dataset ( n  = 1,643) with multidecadal Landsat estimates of C 3 woody cover across 30 African ecosystems to show that there is little relationship between intrataxonomic variation in δ 13 C enamel and vegetation structure. This is especially true when removing forested ecosystems (>80% woody cover)—which numerous lines of evidence suggest are rare in the Plio-Pleistocene fossil record of eastern Africa—from our analyses. Our findings stand in contrast with the common assumption that variation in herbivore δ 13 C enamel values reflects changes in the relative abundance of C 3 –C 4 vegetation. We conclude that analyses using herbivore δ 13 C enamel data to shed light on the environmental context of hominin evolution should look to explicitly community-level approaches for making vegetation inferences. Combining a published dataset of stable carbon isotopes from herbivore tooth enamel with multidecadal Landsat estimates of C 3 woody cover across 30 African ecosystems, the authors show that there is little relationship between intrataxonomic variation in δ 13 C enamel and vegetation structure, leading them to recommend a community-level approach for making vegetation inferences.

In response to DeSantis et al., we describe that the presence of phylogenetic signal in tooth wear dietary niche proxies is likely a result of the evolutionary process. We also address their concerns regarding enforcement of the use of phylogenetic comparative methods by editors of ecology and evolution journals.

In the absence of independent observational data, ecologists and paleoecologists use proxies for the Eltonian niches of species (i.e., the resource or dietary axes of the niche). Some dietary proxies exploit the fact that mammalian teeth experience wear during mastication, due to both tooth‐on‐tooth and food‐on‐tooth interactions. The distribution and types of wear detectible at micro‐ and macroscales are highly correlated with the resource preferences of individuals and, in turn, species. Because methods that quantify the distribution of tooth wear (i.e., analytical tooth wear methods) do so by direct observation of facets and marks on the teeth of individual animals, dietary inferences derived from them are thought to be independent of the clade to which individuals belong. However, an assumption of clade or phylogenetic independence when making species‐level dietary inferences may be misleading if phylogenetic niche conservatism is widespread among mammals. Herein, we test for phylogenetic signal in data from numerous analytical tooth wear studies, incorporating macrowear (i.e., mesowear) and microwear (i.e., low‐magnification microwear and dental microwear texture analysis). Using two measures of phylogenetic signal, heritability (H2) and Pagel's λ, we find that analytical tooth wear data are not independent of phylogeny and failing to account for such nonindependence leads to overestimation of discriminability among species with different dietary preferences. We suggest that morphological traits inherited from ancestral clades (e.g., tooth shape) influence the ways in which the teeth wear during mastication and constrain the foods individuals of a species can effectively exploit. We do not suggest that tooth wear is simply phylogeny in disguise; the tooth wear of individuals and species likely varies within some range that is set by morphological constraints. We therefore recommend the use of phylogenetic comparative methods in studies of mammalian tooth wear, whenever possible. In the absence of independent observational data, ecologists and paleoecologists use proxies for the Eltonian niches of species (i.e., the resource or dietary axes of the niche), some of which exploit the fact that mammalian teeth experience wear during mastication. Because methods that quantify the distribution of tooth wear involve direct observation of facets and marks on the teeth of individual animals, dietary niche inferences derived from them are thought independent of the clade to which individuals belong. However, we show that analytical tooth wear data are not independent of phylogeny and suggest that the mammalian feeding apparatus is an evolutionary module in which correlated changes in the teeth and jaws accompanying an evolutionary shift in diet change the ways in which the teeth wear.

The late Quaternary of North America was marked by prominent ecological changes, including the end‐Pleistocene megafaunal extinction, the spread of human settlements and the rise of agriculture. Here we examine the mechanistic reasons for temporal changes in mammal species association and body size during this time period. Building upon the co‐occurrence results from Lyons et al. (2016) – wherein each species pair was classified as spatially aggregated, segregated or random – we examined body mass differences (BMD) between each species pair for each association type and time period (Late Pleistocene: 40 000 14C–11 700 14C ybp, Holocene: 11 700 14C–50 ybp and Modern: 50–0 yr). In the Late Pleistocene and Holocene, the BMD of both aggregated and segregated species pairs was significantly smaller than the BMD of random pairs. These results are consistent with environmental filtering and competition as important drivers of community structure in both time periods. Modern assemblages showed a breakdown between BMD and co‐occurrence patterns: the average BMD of aggregated, segregated and random species pairs did not differ from each other. Collectively, these results indicate that the late Quaternary mammalian extinctions not only eliminated many large‐bodied species but were followed by a re‐organization of communities that altered patterns of species coexistence and associated differences in body size.

It has been suggested that a shift in diet is one of the key adaptations that distinguishes the genus Homo from earlier hominins, but recent stable isotopic analyses of fossils attributed to Homo in the Turkana Basin show an increase in the consumption of C 4 resources circa 1.65 million years ago, significantly after the earliest evidence for Homo in the eastern African fossil record. These data are consistent with ingesting more C 4 plants, more animal tissues of C 4 herbivores, or both, but it is also possible that this change reflects factors unrelated to changes in the palaeobiology of the genus Homo . Here we use new and published carbon and oxygen isotopic data ( n  = 999) taken from large-bodied fossil mammals, and pedogenic carbonates in fossil soils, from East Turkana in northern Kenya to investigate the context of this change in the isotope signal within Homo . By targeting taxa and temporal intervals unrepresented or undersampled in previous analyses, we were able to conduct the first comprehensive analysis of the ecological context of hominin diet at East Turkana during a period crucial for detecting any dietary and related behavioural differences between early Homo ( H. habilis and/or H. rudolfensis ) and Homo erectus . Our analyses suggest that the genus Homo underwent a dietary shift (as indicated by δ 13 C ena and δ 18 O ena values) that is (1) unrelated to changes in the East Turkana vegetation community and (2) unlike patterns found in other East Turkana large mammals, including Paranthropus and Theropithecus . These data suggest that within the Turkana Basin a dietary shift occurred well after we see the first evidence of early Homo in the region. Carbon and oxygen isotope analysis of sediments and soils from hominin locales in Kenya coupled with results from hominin taxa suggest that a dietary shift from C 3 to C 4 resources occurred in the genus Homo circa 1.65 million years ago despite palaeoenvironmental continuity.

The eastern branch of the Eastern African Rift System (EARS) is the source of a large proportion of the early hominin fossil record, but it covers a tiny fraction (ca. 1%) of the continent. Here we investigate how this mismatch between where fossils are preserved and where hominins probably lived may influence our ability to understand early hominin evolution, using extant mammals as analogues. We show that the eastern branch of the EARS is not an environmentally representative sample of the full species range for nearly all extant rift-dwelling mammals. Likewise, when we investigate published morphometric datasets for extant cercopithecine primates, evidence from the eastern branch alone fails to capture major portions of continental-scale cercopithecine cranial morphospace. We suggest that extant rift-dwelling species should be used as analogues to place confidence intervals on hominin habitat reconstructions. Furthermore, given the north–south orientation of the eastern branch of the EARS, morphoclines that are not aligned along this major north–south axis are likely to be poorly sampled by sites in the eastern branch. There is a pressing need for research on the geography of early hominin morphoclines to estimate how morphologically representative the hominin fossil sample from the eastern branch may be. The Eastern African Rift System (EARS) is a key location for the hominin fossil record, but the fact that it samples a narrow section of the continent has long been known. The authors tackle this known (but largely unaddressed) bias by sampling the distribution and morphospace of extant mammals in the rift, showing that the eastern branch of the EARS fails to capture the full range of diversity and morphology. This approach could be helpful to place confidence intervals on extinct habitat reconstructions, controlling for spatial bias.