Divergence-time estimates for hominins provide insight into encephalization and body mass trends in human evolution

Quantifying speciation times during human evolution is fundamental as it provides a timescale to test for the correlation between key evolutionary transitions and extrinsic factors such as climatic or environmental change. Here, we applied a total evidence dating approach to a hominin phylogeny to estimate divergence times under different topological hypotheses. The time-scaled phylogenies were subsequently used to perform ancestral state reconstructions of body mass and phylogenetic encephalization quotient (PEQ). Our divergence-time estimates are consistent with other recent studies that analysed extant species. We show that the origin of the genus Homo probably occurred between 4.30 and 2.56 million years ago. The ancestral state reconstructions show a general trend towards a smaller body mass before the emergence of Homo, followed by a trend towards a greater body mass. PEQ estimations display a general trend of gradual but accelerating encephalization evolution. The obtained results provide a rigorous temporal framework for human evolution

Quantifying traces of tool use: a novel morphometric analysis of damage patterns on percussive tools

Percussive technology continues to play an increasingly important role in understanding the evolution of tool use. Comparing the archaeological record with extractive foraging behaviors in nonhuman primates has focused on percussive implements as a key to investigating the origins of lithic technology. Despite this, archaeological approaches towards percussive tools have been obscured by a lack of standardized methodologies. Central to this issue have been the use of qualitative, non-diagnostic techniques to identify percussive tools from archaeological contexts. Here we describe a new morphometric method for distinguishing anthropogenically-generated damage patterns on percussive tools from naturally damaged river cobbles. We employ a geomatic approach through the use of three-dimensional scanning and geographical information systems software to statistically quantify the identification process in percussive technology research. This will strengthen current technological analyses of percussive tools in archaeological frameworks and open new avenues for translating behavioral inferences of early hominins from percussive damage patterns.Palaeontological Scientific Trust; National Research Foundation; National Science Foundation [BCS-1128170, BCS-0924476]; Integrative Graduate Education and Research Traineeship Program [DGE-0801634]; George Washington University's Selective Excellence Fund; George Washington University Columbian College Facilitating Fund; Clare Hall College [JRF]; Newnham College [Gibbs Travelling Fellowship] Cambridge; European Research Council [283959]info:eu-repo/semantics/publishedVersio

Reorganization of surviving mammal communities after the end-Pleistocene megafaunal extinction

Large mammals are at high risk of extinction globally. To understand the consequences of their demise for community assembly, we tracked community structure through the end- Pleistocene megafaunal extinction in North America.We decomposed the effects of biotic and abiotic factors by analyzing co-occurrence within the mutual ranges of species pairs. Although shifting climate drove an increase in niche overlap, co-occurrence decreased, signaling shifts in biotic interactions. Furthermore, the effect of abiotic factors on cooccurrence remained constant over time while the effect of biotic factors decreased. Biotic factors apparently played a key role in continental-scale community assembly before the extinctions. Specifically, large mammals likely promoted co-occurrence in the Pleistocene, and their loss contributed to the modern assembly pattern in which co-occurrence frequently falls below random expectations. Includes supplementary materials

Kantis: A new Australopithecus site on the shoulders of the Rift Valley near Nairobi, Kenya

ケニア・ナイロビ郊外で初めて発見されたアウストラロピテクス. 京都大学プレスりリス. 2016-03-24.Most Plio-Pleistocene sites in the Gregory Rift Valley that have yielded abundant fossil hominins lie on the Rift Valley floor. Here we report a new Pliocene site, Kantis, on the shoulder of the Gregory Rift Valley, which extends the geographical range of Australopithecus afarensis to the highlands of Kenya. This species, known from sites in Ethiopia, Tanzania, and possibly Kenya, is believed to be adapted to a wide spectrum of habitats, from open grassland to woodland. The Kantis fauna is generally similar to that reported from other contemporaneous A. afarensis sites on the Rift Valley floor. However, its faunal composition and stable carbon isotopic data from dental enamel suggest a stronger C4 environment than that present at those sites. Although the Gregory Rift Valley has been the focus of paleontologists' attention for many years, surveys of the Rift shoulder may provide new perspective on African Pliocene mammal and hominin evolutio

Early Pleistocene large mammals from Maka’amitalu, Hadar, lower Awash Valley, Ethiopia

The Early Pleistocene was a critical time period in the evolution of eastern African mammal faunas, but fossil assemblages sampling this interval are poorly known from Ethiopia ’ s Afar Depression. Field work by the Hadar Research Project in the Busidima Formation exposures (~2.7 – 0.8 Ma) of Hadar in the lower Awash Valley, resulted in the recovery of an early Homo maxilla (A.L. 666-1) with associated stone tools and fauna from the Maka ’ amitalu basin in the 1990s. These assemblages are dated to ~2.35 Ma by the Bouroukie Tuff 3 (BKT-3). Continued work by the Hadar Research Project over the last two decades has greatly expanded the faunal collection. Here, we provide a comprehensive account of the Maka ’ amitalu large mammals (Artiodactyla, Carnivora, Perissodactyla, Primates, and Proboscidea) and discuss their paleoecological and biochronological signi fi cance. The size of the Maka ’ amitalu assemblage is small compared to those from the Hadar Formation (3.45 – 2.95 Ma) and Ledi-Geraru (2.8 – 2.6 Ma) but includes at least 20 taxa. Bovids, suids, and Theropithecus are common in terms of both species richness and abundance, whereas carnivorans, equids, and megaherbivores are rare. While the taxonomic composition of the Maka ’ amitalu fauna indicates signi fi cant species turnover from the Hadar Formation and Ledi-Geraru deposits, turnover seems to have occurred at a constant rate through time as taxonomic dissimilarity between adjacent fossil assemblages is strongly predicted by their age difference. A similar pattern characterizes functional ecological turnover, with only subtle changes in dietary proportions, body size proportions, and bovid abundances across the composite lower Awash sequence. Biochronological comparisons with other sites in eastern Africa suggest that the taxa recovered from the Maka ’ amitalu are broadly consistent with the reported age of the BKT-3 tuff. Considering the age of BKT-3 and biochronology, a range of 2.4 – 1.9 Ma is most likely for the faunal assemblag

Carbon, nitrogen, and oxygen stable isotopes in modern tooth enamel: A case study from Gorongosa National Park, central Mozambique

The analyses of the stable isotope ratios of carbon (δ13C), nitrogen (δ15N), and oxygen (δ18O) in animal tissues are powerful tools for reconstructing the feeding behavior of individual animals and characterizing trophic interactions in food webs. Of these biomaterials, tooth enamel is the hardest, most mineralized vertebrate tissue and therefore least likely to be affected by chemical alteration (i.e., its isotopic composition can be preserved over millions of years), making it an important and widely available archive for biologists and paleontologists. Here, we present the first combined measurements of δ13C, δ15N, and δ18O in enamel from the teeth of modern fauna (herbivores, carnivores, and omnivores) from the well-studied ecosystem of Gorongosa National Park (GNP) in central Mozambique. We use two novel methods to produce high-precision stable isotope enamel data: (i) the “oxidation-denitrification method,” which permits the measurement of mineral-bound organic nitrogen in tooth enamel (δ15Nenamel), which until now, has not been possible due to enamel’s low organic content, and (ii) the “cold trap method,” which greatly reduces the sample size required for traditional measurements of inorganic δ13Cenamel and δ18Oenamel (from ≥0.5 to ≤0.1 mg), permitting analysis of small or valuable teeth and high-resolution serial sampling of enamel. The stable isotope results for GNP fauna reveal important ecological information about the trophic level, dietary niche, and resource consumption. δ15Nenamel values clearly differentiate trophic level (i.e., carnivore δ15Nenamel values are 4.0‰ higher, on average, than herbivores), δ13Cenamel values distinguish C3 and/or C4 biomass consumption, and δ18Oenamel values reflect local meteoric water (δ18Owater) in the park. Analysis of combined carbon, nitrogen, and oxygen stable isotope data permits geochemical separation of grazers, browsers, omnivores, and carnivores according to their isotopic niche, while mixed-feeding herbivores cannot be clearly distinguished from other dietary groups. These results confirm that combined C, N, and O isotope analyses of a single aliquot of tooth enamel can be used to reconstruct diet and trophic niches. Given its resistance to chemical alteration, the analysis of these three isotopes in tooth enamel has a high potential to open new avenues of research in (paleo)ecology and paleontology

Genomic variation in baboons from central Mozambique unveils complex evolutionary relationships with other Papio species

Background Gorongosa National Park in Mozambique hosts a large population of baboons, numbering over 200 troops. Gorongosa baboons have been tentatively identified as part of Papio ursinus on the basis of previous limited morphological analysis and a handful of mitochondrial DNA sequences. However, a recent morphological and morphometric analysis of Gorongosa baboons pinpointed the occurrence of several traits intermediate between P. ursinus and P. cynocephalus, leaving open the possibility of past and/or ongoing gene flow in the baboon population of Gorongosa National Park. In order to investigate the evolutionary history of baboons in Gorongosa, we generated high and low coverage whole genome sequence data of Gorongosa baboons and compared it to available Papio genomes. Results We confirmed that P. ursinus is the species closest to Gorongosa baboons. However, the Gorongosa baboon genomes share more derived alleles with P. cynocephalus than P. ursinus does, but no recent gene flow between P. ursinus and P. cynocephalus was detected when available Papio genomes were analyzed. Our results, based on the analysis of autosomal, mitochondrial and Y chromosome data, suggest complex, possibly male-biased, gene flow between Gorongosa baboons and P. cynocephalus, hinting to direct or indirect contributions from baboons belonging to the “northern” Papio clade, and signal the presence of population structure within P. ursinus. Conclusions The analysis of genome data generated from baboon samples collected in central Mozambique highlighted a complex set of evolutionary relationships with other baboons. Our results provided new insights in the population dynamics that have shaped baboon diversity.info:eu-repo/semantics/publishedVersio

The first Miocene fossils from coastal woodlands in the southern East African Rift

The Miocene was a key time in the evolution of African ecosystems witnessing the origin of the African apes and the isolation of eastern coastal forests through an expanding arid corridor. Until recently, however, Miocene sites from the southeastern regions of the continent were unknown. Here, we report the first Miocene fossil teeth from the shoulders of the Urema Rift in Gorongosa National Park, Mozambique. We provide the first 1) radiometric ages of the Mazamba Formation, 2) reconstructions of paleovegetation in the region based on pedogenic carbonates and fossil wood, and 3) descriptions of fossil teeth. Gorongosa is unique in the East African Rift in combining marine invertebrates, marine vertebrates, reptiles, terrestrial mammals, and fossil woods in coastal paleoenvironments. The Gorongosa fossil sites offer the first evidence of woodlands and forests on the coastal margins of southeastern Africa during the Miocene, and an exceptional assemblage of fossils including new species

Paleoecological reconstructions of c.4 Ma hominin sites from the Omo-Turkana basin using fossil bovidae

Leakey Foundation Sigma Xi Explorers Club Washington Group inc Evolving Earth Foundation Cosmos Club Foundation Lewis N. Cotlow Fun