Parvimico materdei gen. et sp. nov.: A new platyrrhine from the Early Miocene of the Amazon Basin, Peru1 Publication date: September 2019 Source: Journal of Human Evolution, Volume 134 Author(s): Richard F. Kay, Lauren A. Gonzales, Wout Salenbien, Jean-Noël Martinez, Siobhán B. Cooke, Luis Angel Valdivia, Catherine Rigsby, Paul A. Baker Abstract Three field seasons of exploration along the Río Alto Madre de Dios in Peruvian Amazonia have yielded a fauna of micromammals from a new locality AMD-45, at ∼12.8°S. So far we have identified the new primate described here as well as small caviomorph rodents, cenolestoid marsupials, interatheriid notoungulates, xenarthrans, fish, lizards and invertebrates. The site is in the Bala Formation as exposed where the river transects a syncline. U-Pb dates on detrital zircons constrain the locality's age at between 17.1 ± 0.7 Ma and 18.9 ± 0.7 Ma, making the fauna age-equivalent to that from the Pinturas Formation and the older parts of the Santa Cruz Formation of Patagonian Argentina (Santacrucian). The primate specimen is an unworn M1 of exceptionally small size (equivalent in size to the extant callitrichine, Callithrix jacchus, among the smallest living platyrrhines and the smallest Eocene-Early Miocene platyrrhine yet recorded). Despite its small size it is unlike extant callitrichines in having a prominent cingulum hypocone. Based on the moderate development of the buccal crests, this animal likely had a diet similar to that of frugivorous callitrichines, and distinctly different from the more similarly-sized gummivores, Cebuella and C. jacchus. The phyletic position of the new taxon is uncertain, especially given the autapomorphic character of the tooth as a whole. Nevertheless, its unusual morphology hints at a wholly original and hitherto unknown Amazonian fauna, and reinforces the impression of the geographic separation of the Amazonian tropics from the more geographically isolated southerly parts of the continent in Early Miocene times.

Comparative morphology and ontogeny of the thoracolumbar transition in great apes, humans, and fossil hominins Publication date: September 2019 Source: Journal of Human Evolution, Volume 134 Author(s): Thierra K. Nalley, Jeremiah E. Scott, Carol V. Ward, Zeresenay Alemseged Abstract Variation among extant hominoid taxa in the anatomy of the thoracolumbar vertebral transition is well-established and constitutes an important framework for making inferences about posture and locomotion in fossil hominins. However, little is known about the developmental bases of these differences, posing a challenge when interpreting the morphology of juvenile hominins. In this study, we investigated ontogenetic variation in the thoracolumbar transition of juvenile and adult great apes, humans, and fossils attributed to Australopithecus and early Pleistocene Homo erectus. For each vertebra involved in the transition, we quantified functionally relevant aspects of zygapophyseal form: facet curvature in the transverse plane, facet orientation relative to midline, and the shift in these variables across the thoracolumbar transition, from the antepenultimate rib-bearing thoracic to the first lumbar vertebra (L1). Among extant hominids, adult individuals of Pan and Homo exhibit a greater shift in facet morphology across the thoracolumbar transition in comparison to Gorilla and Pongo. This pattern is driven by interspecific differences in the L1 facets, with those of chimpanzees and humans being more curved and more sagittally oriented. Chimpanzees and humans also experience more change in facet morphology during development relative to gorillas and orangutans. Humans differ from chimpanzees in achieving their adultlike configuration much earlier in development. The fossil specimens indicate that early hominins had adult morphologies that were similar to those of extant Homo and Pan, and that they achieved their adult morphologies early in development, like extant humans. Although it is unclear why adult chimpanzees and hominins share an adult morphology, we speculate that the early acquisition of adultlike L1 zygapophyseal morphology in hominins is an evolutionary novelty related to conferring stability to a relatively long lumbar spine as young individuals are learning to walk bipedally.

First maxilla of a late Miocene hominid from Thailand and the evolution of pongine derived characters Publication date: September 2019 Source: Journal of Human Evolution, Volume 134 Author(s): Yaowalak Chaimanee, Vincent Lazzari, Kamol Chaivanich, Jean-Jacques Jaeger Abstract The evolutionary history of Asian Miocene hominids (great apes and humans) remains poorly documented, obscuring the ancestry of orangutan (Pongo). Khoratpithecus from the middle and late Miocene of Thailand and Myanmar was previously documented only by mandibles and isolated teeth. It has been interpreted as the closest relative of Pongo based on shared derived mandible characters such as symphyseal morphology and the lack of anterior digastric muscle scars. Here we describe a new maxilla, MFT-K176, which originates from the same sedimentary unit as the holotype mandible of Khoratpithecus piriyai from the late Miocene in Nakhon Ratchasima province, Northeastern Thailand. The new maxilla displays a unique subnasal morphology with several derived characters being shared only with Sivapithecus and Pongo, confirming its attribution to the pongine clade. However, it differs from other known Asian hominids by it subnasal and dental morphology, showing more similar to Khoratpithecus chiangmuanensis teeth. Metric similarities with the mandible of K. piriyai corroborate the referral of MFT-K176 to Khoratpithecus. However, as associated upper and lower teeth would be required to evaluate the latter assertion more conclusively, we attribute it provisionally to cf. Khoratpithecus sp. Other anatomical characters from the clivus, the palate and the molars are peculiar for this hominid but do not exclude it from a sister group relationship with Pongo. This new maxilla plays a pivotal role in understanding that Ankarapithecus occupies a more basal position within the pongine clade and supports the exclusion of Lufengpithecus from this clade.

Poggetti Vecchi (Tuscany, Italy): A late Middle Pleistocene case of human–elephant interaction Publication date: August 2019 Source: Journal of Human Evolution, Volume 133 Author(s): Biancamaria Aranguren, Stefano Grimaldi, Marco Benvenuti, Chiara Capalbo, Floriano Cavanna, Fabio Cavulli, Francesco Ciani, Giacomo Comencini, Claudia Giuliani, Giuditta Grandinetti, Marta Mariotti Lippi, Federico Masini, Paul Peter Anthony Mazza, Pasquino Pallecchi, Fabio Santaniello, Andrea Savorelli, Anna Revedin Abstract A paleosurface with a concentration of wooden-, bone-, and stone-tools interspersed among an accumulation of fossil bones, largely belonging to the straight-tusked elephant Palaeoloxodon antiquus, was found at the bottom of a pool, fed by hot springs, that was excavated at Poggetti Vecchi, near Grosseto (Tuscany, Italy). The site is radiometrically dated to the late Middle Pleistocene, around 171,000 years BP. Notable is the association of the artifacts with the elephant bones, and in particular the presence of digging sticks made from boxwood (Buxus sp.). Although stone tools show evidence of use mainly on animal tissues, indicating some form of interaction between hominins and animals, the precise use of the sticks is unclear. Here we discuss about the role played by the hominins at the site: paleobiological and taphonomic evidence indicates that the elephants died by a natural cause and were butchered soon after their death. The associated paleontological and archeological evidence from this site provides fresh insights into the behavior of early Neanderthals in Central Italy. The discovery of Poggetti Vecchi shows how opportunistically flexible Neanderthals were in response to environmental contingencies.

Endostructural morphology in hominoid mandibular third premolars: Geometric morphometric analysis of dentine crown shape Publication date: August 2019 Source: Journal of Human Evolution, Volume 133 Author(s): Thomas W. Davies, Lucas K. Delezene, Philipp Gunz, Jean-Jacques Hublin, Matthew M. Skinner Abstract In apes, the mandibular third premolar (P3) is adapted for a role in honing the large upper canine. The role of honing was lost early in hominin evolution, releasing the tooth from this functional constraint and allowing it to respond to subsequent changes in masticatory demands. This led to substantial morphological changes, and as such the P3 has featured prominently in systematic analyses of the hominin clade. The application of microtomography has also demonstrated that examination of the enamel-dentine junction (EDJ) increases the taxonomic value of variations in crown morphology. Here we use geometric morphometric techniques to analyze the shape of the P3 EDJ in a broad sample of fossil hominins, modern humans, and extant apes (n = 111). We test the utility of P3 EDJ shape for distinguishing among hominoids, address the affinities of a number of hominin specimens of uncertain taxonomic attribution, and characterize the changes in P3 EDJ morphology across our sample, with particular reference to features relating to canine honing and premolar ‘molarization’. We find that the morphology of the P3 EDJ is useful in taxonomic identification of individual specimens, with a classification accuracy of up to 88%. The P3 EDJ of canine-honing apes displays a tall protoconid, little metaconid development, and an asymmetrical crown shape. Plio-Pleistocene hominin taxa display derived masticatory adaptations at the EDJ, such as the molarized premolars of Australopithecus africanus and Paranthropus, which have well-developed marginal ridges, an enlarged talonid, and a large metaconid. Modern humans and Neanderthals display a tall dentine body and reduced metaconid development, a morphology shared with premolars from Mauer and the Cave of Hearths. Homo naledi displays a P3 EDJ morphology that is unique among our sample; it is quite unlike Middle Pleistocene and recent Homo samples and most closely resembles Australopithecus, Paranthropus and early Homo specimens.

Understanding stone tool-making skill acquisition: Experimental methods and evolutionary implications Publication date: August 2019 Source: Journal of Human Evolution, Volume 133 Author(s): Justin Pargeter, Nada Khreisheh, Dietrich Stout Abstract Despite its theoretical importance, the process of stone tool-making skill acquisition remains understudied and poorly understood. The challenges and costs of skill learning constitute an oft-neglected factor in the evaluation of alternative adaptive strategies and a potential source of bias in cultural transmission. Similarly, theory and data indicate that the most salient neural and cognitive demands of stone tool-making should occur during learning rather than expert performance. Unfortunately, the behavioral complexity and extensive learning requirements that make stone knapping skill acquisition an interesting object of study are the very features that make it so challenging to investigate experimentally. Here we present results from a multidisciplinary study of Late Acheulean handaxe-making skill acquisition involving twenty-six naïve participants and up to 90 hours training over several months, accompanied by a battery of psychometric, behavioral, and neuroimaging assessments. In this initial report, we derive a robust quantitative skill metric for the experimental handaxes using machine learning algorithms, reconstruct a group-level learning curve, and explore sources of individual variation in learning outcomes. Results identify particular cognitive targets of selection on the efficiency or reliability of tool-making skill acquisition, quantify learning costs, highlight the likely importance of social support, motivation, persistence, and self-control in knapping skill acquisition, and illustrate methods for reliably reconstructing ancient learning processes from archaeological evidence.

New electron spin resonance (ESR) ages from Geißenklösterle Cave: A chronological study of the Middle and early Upper Paleolithic layers Publication date: August 2019 Source: Journal of Human Evolution, Volume 133 Author(s): Maïlys Richard, Christophe Falguères, Hélène Valladas, Bassam Ghaleb, Edwige Pons-Branchu, Norbert Mercier, Daniel Richter, Nicholas J. Conard Abstract Geißenklösterle Cave (Germany) is one of the most important Paleolithic sites in Europe, as it is characterized by human occupation during the Middle and early Upper Paleolithic. Aurignacian layers prior to 37–38 ka cal BP feature both musical and figurative art objects that are linked to the early arrival in Europe of Homo sapiens. Middle Paleolithic layers yielded lithic artifacts attributed to Homo neanderthalensis. Since human occupation at the site is attributed to both Neanderthals and modern humans, chronology is essential to clarify the issues of Neanderthal disappearance, modern human expansion in Europe, and the origin of the Aurignacian in Western Europe. Electron spin resonance (ESR) dating was performed on fossil tooth enamel collected from the Middle Paleolithic layers, which are beyond the radiocarbon dating range, and from the nearly sterile ‘transitional’ geological horizon (GH) 17 and the lower Aurignacian deposits, to cross-check ESR ages with previous radiocarbon, thermoluminescence and ESR age results. The Middle Paleolithic layers were dated between 94 ± 10 ka (GH 21) and 55 ± 6 ka (GH 18) by ESR on tooth enamel. Mean ages for GH 17, at 46 ± 3 ka, and for the lower Aurignacian layers, at 37 ± 3 ka, are in agreement with previous dating results, thus supporting the reliability of ESR chronology for the base of the sequence where dating comparisons are not possible. These results suggest that Neanderthals occupied the site from Marine Isotope Stage (MIS) 5 to the second half of MIS 3 and confirm the antiquity of early Aurignacian deposits. The presence of an almost sterile layer that separates Middle and Upper Paleolithic occupations could be related to the abandonment of the site by Neanderthals, possibly during Heinrich Stadial 5 (ca. 49–47 ka), thus before the arrival of H. sapiens in the area around 42 ka cal BP. These dates for the Middle Paleolithic of the Swabian Jura represent an important contribution to the prehistory of the region, where nearly all of the excavations were conducted decades ago and prior to the development of reliable radiometric dating beyond the range of radiocarbon.

The radiation of macaques out of Africa: Evidence from mitogenome divergence times and the fossil record Publication date: August 2019 Source: Journal of Human Evolution, Volume 133 Author(s): Christian Roos, Maximilian Kothe, David M. Alba, Eric Delson, Dietmar Zinner Abstract Fossil evidence indicates that numerous catarrhine clades of African origin expanded or shifted their ranges into Eurasia, among them macaques Macaca Lacépède, 1799. Macaques represent the sister taxon of African papionins and can thus be used as a model comparing an ‘out-of-Africa’ with an intra-African, e.g., baboons—Papio Erxleben, 1777 evolutionary history. The first step for such a comparison is to establish a well-resolved phylogeny of macaques with reliably estimated divergence times and to compare it with that of baboons and the fossil record. Therefore, we used mitochondrial (mtDNA) genome data deposited in GenBank of 16 out of 23 extant macaque species and of all six baboon taxa. We reconstructed phylogenetic trees using maximum-likelihood and Bayesian inferences and dated differentiation events using three fossil-based calibration sets. The obtained tree topology is in agreement with findings from earlier mtDNA studies, but yielded stronger nodal supports. We observed some para- and polyphylies in macaques and baboons, suggesting that ancient gene flow among divergent lineages has been common in both genera. Our divergence time estimates are in broad agreement with earlier findings and with the fossil record. Macaques started to diversify 7.0–6.7 Ma, followed by a stepwise radiation into several species groups in Asia, whereas baboons commenced diversification around 2.2 Ma. Accordingly, divergence of species groups and species in macaques clearly predates divergences in baboons. Based on our phylogenetic results with estimated divergence times and the recorded chronostratigraphic ranges of extinct macaque and baboon taxa, we compare the evolutionary radiations of both genera from paleobiogeographic and adaptive viewpoints.

Temporal bone pneumatization: The case of Australopithecus sediba and its implications for the definition of the genus Homo Publication date: August 2019 Source: Journal of Human Evolution, Volume 133 Author(s): Antoine Balzeau

Seasonal and habitat effects on the nutritional properties of savanna vegetation: Potential implications for early hominin dietary ecology Publication date: August 2019 Source: Journal of Human Evolution, Volume 133 Author(s): Oliver C.C. Paine, Abigale Koppa, Amanda G. Henry, Jennifer N. Leichliter, Daryl Codron, Jacqueline Codron, Joanna E. Lambert, Matt Sponheimer Abstract The African savannas that many early hominins occupied likely experienced stark seasonality and contained mosaic habitats (i.e., combinations of woodlands, wetlands, grasslands, etc.). Most would agree that the bulk of dietary calories obtained by taxa such as Australopithecus and Paranthropus came from the consumption of vegetation growing across these landscapes. It is also likely that many early hominins were selective feeders that consumed particular plants/plant parts (e.g., leaves, fruit, storage organs) depending on the habitat and season within which they were foraging. Thus, improving our understanding of how the nutritional properties of potential hominin plant foods growing in modern African savanna ecosystems respond to season and vary by habitat will improve our ability to model early hominin dietary behavior. Here, we present nutritional analyses (crude protein and acid detergent fiber) of plants growing in eastern and southern African savanna habitats across both wet and dry seasons. We find that many assumptions about savanna vegetation are warranted. For instance, plants growing in our woodland habitats have higher average protein/fiber ratios than those growing in our wetland and grassland transects. However, we find that the effects of season and habitat are complex, an example being the unexpectedly higher protein levels we observe in the grasses and sedges growing in our Amboseli wetlands during the dry season. Also, we find significant differences between the vegetation growing in our eastern and southern African field sites, particularly among plants using the C4 photosynthetic pathway. This may have implications for the differences we see between the stable carbon isotope compositions and dental microwear patterns of eastern and southern African Paranthropus species, despite their shared, highly derived craniodental anatomy.