Some observations on enamel thickness and enamel prism packing in the miocene hominoid Otavipithecus namibiensis

Otavipithecus namibiensis is currently the sole representative of a Miocene hominoid radiation in subequatorial Africa. Several nondestructive techniques, such as computed tomography (CT) and confocal microscopy (CFM), can provide useful information about dental characteristics in this southern African Miocene hominoid. Our studies suggest that the molars of Otavipithecus are characterized by (1) thin enamel and (2) a predominance of pattern 1 enamel prism. Together, these findings provide little support for the recent suggestion of an Afropithecini clade consisting of Otavipithecus, Heliopithecus, and Afropithecus. Instead, they lend some (though not conclusive) support to the suggestion of an Otavipithecus/African ape clade distinct from Afropithecus. © 1995 Wiley-Liss, Inc.     

Brief communication: New primate remains from the Miocene of Namibia,Southern Africa

Miocene primates from southern Africa are extremely rare. For this reason we wish to place on record several interesting new fossil primate specimens recently recovered from the Miocene sites of Berg Aukas and Harasib in the Otavi Mountain region of northern Namibia. The new finds consist of a virtually complete atlas vertebra from Berg Aukas attributable to the hominoid Otavipithecus namibiensis and two teeth and four postcranial fragments from Harasib referrable to Cercopithecoidea. The atlas vertebra exhibits anatomical characteristics intermediate between those of modern cercopithecoids and hominoids which may be indicative of a transition from pronograde to orthograde postures. The cercopithecoid remains show that the earliest Old World monkeys known from southern Africa were small, approximately the size of vervet monkeys. These new specimens are important because they provide the first evidence relating to possible positional behaviors of Otavipithecus and the earliest fossil record of cercopithecoids from southern Africa. © 1996 Wiley-Liss, Inc.     

Our ancestors' ancestor: Ouranopithecus is a greek link in human ancestry

Recent discoveries of the late Miocene hominoid Ouranopithecus shed new light on the evolution of hominids. These discoveries result from the strategy of the Allied armies during the First World War. In the midst of “the war to end all wars,” the North African soldiers of Camille Arambourg excavated the first mammalian fossils found in northern Greece, in the region of Macedonia, the country of Alexander the Great. On the tracks of these strange paleontological pioneers, a modern French and Greek team has unearthed a large hominoid primate, a missing link between fossilapes and primitive Australopithecus, which lived in southeastern Europe 9 to 10 million years ago. A reconstruction of Ouranopithecus and its surroundings gives us a rare glimpse into the world of the earliest hominids.     

The evolution of intergroup tolerance in nonhuman primates and humans

Primate individuals use a variety of strategies in intergroup encounters, from aggression to tolerance; however, recent focus on the evolution of either warfare or peace has come at the cost of characterizing this variability. We identify evolutionary advantages that may incentivize tolerance toward extra‐group individuals in humans and nonhuman primates, including enhanced benefits in the domains of transfer, mating, and food acquisition. We highlight the role these factors play in the flexibility of gorilla, chimpanzee, bonobo, and human behavior. Given humans have an especially broad range of intergroup behavior, we explore how the human foraging ecology, especially large spatial and temporal fluctuations in resource availability, may have selected for a greater reliance on tolerant between‐community relationships—relationships reinforced by status acquisition and cultural institutions. We conclude by urging careful, theoretically motivated study of behavioral flexibility in intergroup encounters in humans and the nonhuman great apes.     

The morphology and evolutionary history of the glenohumeral joint of hominoids: A review

The glenohumeral joint, the most mobile joint in the body of hominoids, is involved in the locomotion of all extant primates apart from humans. Over the last few decades, our knowledge of how variation in its morphological characteristics relates to different locomotor behaviors within extant primates has greatly improved, including features of the proximal humerus and the glenoid cavity of the scapula, as well as the muscles that function to move the joint (the rotator cuff muscles). The glenohumeral joint is a region with a strong morphofunctional signal, and hence, its study can shed light on the locomotor behaviors of crucial ancestral nodes in the evolutionary history of hominoids (e.g., the last common ancestor between humans and chimpanzees). Hominoids, in particular, are distinct in showing round and relatively big proximal humeri with lowered tubercles and flattened and oval glenoid cavities, morphology suited to engage in a wide range of motions, which enables the use of locomotor behaviors such as suspension. The comparison with extant taxa has enabled more informed functional interpretations of morphology in extinct primates, including hominoids, from the Early Miocene through to the emergence of hominins. Here, I review our current understanding of glenohumeral joint functional morphology and its evolution throughout the Miocene and Pleistocene, as well as highlighting the areas where a deeper study of this joint is still needed.     

Age at first molar emergence in early Miocene Afropithecus turkanensis and life-history evolution in the Hominoidea

Among primates, age at first molar emergence is correlated with a variety of life history traits. Age at first molar emergence can therefore be used to broadly infer the life histories of fossil primate species. One method of determining age at first molar emergence is to determine the age at death of fossil individuals that were in the process of erupting their first molars. This was done for an infant partial mandible of Afropithecus turkanensis (KNM-MO 26) from the approximately 17.5 Ma site of Moruorot in Kenya. A range of estimates of age at death was calculated for this individual using the permanent lateral incisor germ preserved in its crypt, by combining the number and periodicity of lateral enamel perikymata with estimates of the duration of cuspal enamel formation and the duration of the postnatal delay in the inception of crown mineralization. Perikymata periodicity was determined using daily cross striations between adjacent Retzius lines in thin sections of two A. turkanensis molars from the nearby site of Kalodirr. Based on the position of the KNM-MO 26 M(1)in relation to the mandibular alveolar margin, it had not yet undergone gingival emergence. The projected time to gingival emergence was estimated based on radiographic studies of M(1)eruption in extant baboons and chimpanzees.The estimates of age at M(1)emergence in KNM-MO 26 range from 28.2 to 43.5 months, using minimum and average values from extant great apes and humans for the estimated growth parameters. Even the absolute minimum value is well outside the ranges of extant large Old World monkeys for which there are data (12.5 to <25 months), but is within the range of chimpanzees (25.7 to 48.0 months). It is inferred, therefore, that A. turkanensis had a life history profile broadly like that of Pan. This is additional evidence to that provided by Sivapithecus parvada (Function, Phylogeny, and Fossils: Miocene Hominoid Evolution and Adaptations, 1997, 173) that the prolonged life histories characteristic of extant apes were achieved early in the evolutionary history of the group. However, it is unclear at present whether life-history prolongation in apes represents the primitive catarrhine pace of life history extended through phyletic increase in body mass, or whether it is derived with respect to a primitive, size-adjusted life history that was broadly intermediate between those of extant hominoids and cercopithecoids. Life history evolution in primates as a whole may have occurred largely through a series of grade-shifts, with the establishment of fundamental life-history profiles early in the histories of major higher taxa. These may have included shifts that were largely body mass dependent, as well as those that occurred in the absence of significant changes in body mass.     

The Fayum primate forest: Did it exist?

The primates have the reputation of being essentially arboreal, forest-adapted animals. Yet there are many genera and species that inhabit an extremely wide array of non-forest habitats. Nevertheless, palaeoprimatologists often tend to depict fossil primate habitats as being more arboreal and more forest-like than is justified by the facts. It is worthwhile, therefore, to reconsider some current interpretations. In this paper, evidence of the Fayum Oligocene primate deposits are reviewed and discussed. The following conclusions emerge:(1) The large number of primate species indicates that the Fayum ecosystem was an optimum or near-optimum habitat for primates. (2) The lithological characteristics point to a sahélien type of climate. (3) The calcified and silicified root systems, having diameters up to 4 cm, suggest a sahélien type of shrub, bushland and/or small-tree vegetation. (4) The large fossilized logs cannot have grown on the spot and apparently represent driftwood from a more humid climatic belt in the south, as is indicated by damage resulting from fluvial transportation and by palaeobotanical data. (5) There may have been some minor patches or strips of medium-height forests and/or wood-lands in the Fayum delta, but there is no evidence of these.Thus the tall forest in which the earliest known African primates are currently supposed to have lived probably never existed. Grounds for this conclusion were presented by Unger 121 years ago, by Beadnell 75 years ago and by Kräusel 41 years ago, but sank into oblivion. The classic image of the primates as arboreal specialists seems to have interfered with seeing the facts. However, more extensive verification of the evidence by means of palaeobotanical research is still required. The fossil material to do so is readily available.     

A cercopithecid primate from the late miocene of Molayan,Afghanistan, with remarks onMesopithecus

The first fossil primate discovered in Afghanistan comes from the Late Miocene of Molayan, Khurdkabul Basin. The materials consist of an almost-complete juvenile mandible and an isolated P₃. These two specimens do not significantly differ from thePikermi Mesopithecus pentelicus and are assigned to this species. The primate mandible from the Late Miocene of Maragheh, Iran, which has always been referred by all authors toM. pentelicus, differs from the Pikermi and Molayan materials. It must be assigned to another taxon, probably a new one. The geographic range ofM. pentelicus turns out to be considerably wider in view of the discovery of the species in Molayan, eastern Afghanistan.     

The relationships among jaw‐muscle fiber architecture,jaw morphology,and feeding behavior in extant apes and modern humans

The jaw‐closing muscles are responsible for generating many of the forces and movements associated with feeding. Muscle physiologic cross‐sectional area (PCSA) and fiber length are two architectural parameters that heavily influence muscle function. While there have been numerous comparative studies of hominoid and hominin craniodental and mandibular morphology, little is known about hominoid jaw‐muscle fiber architecture. We present novel data on masseter and temporalis internal muscle architecture for small‐ and large‐bodied hominoids. Hominoid scaling patterns are evaluated and compared with representative New‐ (Cebus) and Old‐World (Macaca) monkeys. Variation in hominoid jaw‐muscle fiber architecture is related to both absolute size and allometry. PCSAs scale close to isometry relative to jaw length in anthropoids, but likely with positive allometry in hominoids. Thus, large‐bodied apes may be capable of generating both absolutely and relatively greater muscle forces compared with smaller‐bodied apes and monkeys. Compared with extant apes, modern humans exhibit a reduction in masseter PCSA relative to condyle‐M₁ length but retain relatively long fibers, suggesting humans may have sacrificed relative masseter muscle force during chewing without appreciably altering muscle excursion/contraction velocity. Lastly, craniometric estimates of PCSAs underestimate hominoid masseter and temporalis PCSAs by more than 50% in gorillas, and overestimate masseter PCSA by as much as 30% in humans. These findings underscore the difficulty of accurately estimating jaw‐muscle fiber architecture from craniometric measures and suggest models of fossil hominin and hominoid bite forces will be improved by incorporating architectural data in estimating jaw‐muscle forces. Am J Phys Anthropol 151:120–134, 2013. © 2013 Wiley Periodicals, Inc.     

Major features in the evolution of early hominoid locomotion

Evolution of hominoid locomotion is a traditional topic in primate evolution. Views have changed during the last decade because a number of crucial differences between early and advanced hominoid morphologies have been demonstrated. Increasing evidence on primate behaviour and ecology show that any direct analogies between living and fossil hominoids must be made extremely carefully. The necessity of synthesizing data on primate behaviour, locomotion, morphology and ecology and simultaneously defining the framework in which the data should be interpreted are explained. Results of our studies of ontogeny of locomotor and behavioural patterns (LBP) are presented that could help identify the main features of early hominoid locomotor patterns (LP) and the mechanisms of their changes. The early hominoid LP was different from those of pronograde monkeys and specialized antipronograde living apes. Some similar features could be expected between early hominoid LP and the LP of ceboid monkeys. Analogous mechanisms of change of LBP exist in all groups of living higher primates. Crucial early mechanisms of change are the ontogenetic shifts in LBP connected with ethoecological changes. Analysis of fossil evidence has shown that Miocene hominoids differ morphologically from any group of living primates. Certain features present in Miocene hominoids could be found in Atelinae and living Asian apes but they are limited to some functional regions of the postcrania only. Consequently the early hominoid general LP can not be strictly analogous either to that of any monkey group or to the LP of apes. We suppose that certain pronograde adaptations, such as climbing, bipedality, limited suspensory activity and sitting constituted the main part of their LP.     

The nature of the transition in the dental mechanism from pongids to hominids

Many recent discoveries of Ramapithecus, and of probably ground-living dryopithecines, Dryopithecus (subgenus Sivapithecus), clarify the nature of the transition of the dental mechanism from that of pongids to the hominid stage with reduced canines and flattened cheek teeth with thick enamel.Faunal correlation with potassium/argon dated sites indicates that Sivapithecus and Ramapithecus appeared in the Old World about the same time, approximately 13 million years ago. The thickened molar enamel of these hominoids suggests a terrestrial adaptation in both groups, probably resulting from climatic changes. This adaptation was not necessarily a unique event in the ancestry of the two genera, for species of the two seem to have been different sizes when the change was made.New Ramapithecus finds come from Pyrgos, near Athens, from Çandir in Anatolia, and from Rudabánya, Hungary. At the latter site various specimens preserve all upper and lower teeth in place, while the Çandir and Pyrgos mandibles give important new information about symphyseal structure and orientation, as well as about arcade arrangement. The Rudabánya finds confirm, as do the others, marked facial foreshortening, relatively orthal incisors, anteriorly abbreviated mandible and canine reduction in Ramapithecus. The dental mechanics of Ramapithecus suggested from earlier described finds recovered in the Siwalik deposits of India and Pakistan, as well as at Fort Ternan, Kenya are clarified by the finds from Athens, Anatolia, and Hungary. Like Australopithecus, Ramapithecus mandibles have well-developed double transverse, shallow but transversely thick horizontal rami and anteriorly shifted, vertically oriented, deep ascending branches. These addes resemblances increase the probability that Ramapithecus is in or near the ancestry of Australopithecus and other hominids.     

The influence of multi‐scale environmental variables on the distribution of terricolous lichens in a fog desert

Question: How do environmental variables in a hyper‐arid fog desert influence the distribution patterns of terricolous lichens on both macro‐ and micro‐scales? Location: Namib Desert, Namibia. Methods: Sites with varying lichen species cover were sampled for environmental variables on a macro‐scale (elevation, slope degree, aspect, proximity to river channels, and fog deposition) and on a micro‐scale (soil structure and chemistry). Macro‐scale and micro‐scale variables were analysed separately for associations with lichen species cover using constrained ordination (DCCA) and unconstrained ordination (DCA). Explanatory variables that dominated the first two axes of the constrained ordinations were tested against a lichen cover gradient. Results: Elevation and proximity to river channels were the most significant drivers of lichen species cover in the macro‐scale DCCA, but results of the DCA suggest that a considerable percentage of variation in lichen species cover is unexplained by these variables. On a micro‐scale, sediment particle size explained a majority of lichen community variations, followed by soil pH. When both macro and micro‐scale variables were tested along a lichen cover gradient, soil pH was the only variable to show a significant relationship to lichen cover. Conclusion: The findings suggest that landscape variables contribute to variations in lichen species cover, but that stronger links occur between lichen growth and small‐scale variations in soil characteristics, supporting the need for multi‐scale approaches in the management of threatened biological soil crust communities and related ecosystem functions.     

Additional postcranial elements of Teilhardina belgica: The oldest European primate

Teilhardina belgica is one of the earliest fossil primates ever recovered and the oldest fossil primate from Europe. As such, this taxon has often been hypothesized as a basal tarsiiform on the basis of its primitive dental formula with four premolars and a simplified molar cusp pattern. Until recently [see Rose et al.: Am J Phys Anthropol 146 (2011) 281–305; Gebo et al.: J Hum Evol 63 (2012) 205–218], little was known concerning its postcranial anatomy with the exception of its well‐known tarsals. In this article, we describe additional postcranial elements for T. belgica and compare these with other tarsiiforms and with primitive adapiforms. The forelimb of T. belgica indicates an arboreal primate with prominent forearm musculature, good elbow rotational mobility, and a horizontal, rather than a vertical body posture. The lateral hand positions imply grasps adaptive for relatively large diameter supports given its small body size. The hand is long with very long fingers, especially the middle phalanges. The hindlimb indicates foot inversion capabilities, frequent leaping, arboreal quadrupedalism, climbing, and grasping. The long and well‐muscled hallux can be coupled with long lateral phalanges to reconstruct a foot with long grasping digits. Our phyletic analysis indicates that we can identify several postcranial characteristics shared in common for stem primates as well as note several derived postcranial characters for Tarsiiformes. Am J Phys Anthropol 156:388–406, 2015. © 2014 Wiley Periodicals, Inc.     

Percussive technology in human evolution: an introduction to a comparative approach in fossil and living primates

Percussive technology is part of the behavioural suite of several fossil and living primates. Stone Age ancestors used lithic artefacts in pounding activities, which could have been most important in the earliest stages of stone working. This has relevant evolutionary implications, as other primates such as chimpanzees and some monkeys use stone hammer-and-anvil combinations to crack hard-shelled foodstuffs. Parallels between primate percussive technologies and early archaeological sites need to be further explored in order to assess the emergence of technological behaviour in our evolutionary line, and firmly establish bridges between Primatology and Archaeology. What are the anatomical, cognitive and ecological constraints of percussive technology? How common are percussive activities in the Stone Age and among living primates? What is their functional significance? How similar are archaeological percussive tools and those made by non-human primates? This issue of Phil. Trans. addresses some of these questions by presenting case studies with a wide chronological, geographical and disciplinary coverage. The studies presented here cover studies of Brazilian capuchins, captive chimpanzees and chimpanzees in the wild, research on the use of percussive technology among modern humans and recent hunter–gatherers in Australia, the Near East and Europe, and archaeological examples of this behaviour from a million years ago to the Holocene. In summary, the breadth and depth of research compiled here should make this issue of Philosophical Transactions of the Royal Society B, a landmark step forward towards a better understanding of percussive technology, a unique behaviour shared by some modern and fossil primates.