Defence of bipedalism

The long-unresolved and much publicized puzzle of how human ancestors could have ventured upon habitual bipedalism without making themselves highly vulnerable to predation derives from a misunderstanding of the principles upon which predator-prey relations work. Erect stature, regardless of locomotion proficiency, in fact enhances passive, and not simply active, defence against predators. This was the necessary condition, the security ‘cover’, for selection for the elaboration of bipedal behavior. As illustration, I analyse the defence systems ofPan troglodytes and the hunting techniques of their predators, known and potential, in order to hypothesize the defence impact of bipedal selection on the former; the relevance of human experience with felid predators, in particular, is also then explored. Despite known major differences in the late Miocene mammalian predator guild, the predator-prey framework is likely to have been much the same as to-day, making the findings applicable to the situation of proto-hominids. Once it is accepted selection pressure for bipedalism was originally focused on posture and not locomotion, the mystery of its emergence disappears.     

New views on primate origins

Most primates live in trees, and many of them have strikingly human-like hands and faces. Scientists who study primate evolution agree that these two facts must be connected in some way. The details, however, are a matter of debate. Early theories explained the human-like peculiarities of primates simply as arboreal adaptations. More recent accounts have traced the origins of these peculiarities to more specific ways of arboreal life, involving leaping locomotion, shrub-layer foraging, visually guided predation on insects, or fruit-eating.     

Arboreality,terrestriality and bipedalism

The full publication of Ardipithecus ramidus has particular importance for the origins of hominin bipedality, and strengthens the growing case for an arboreal origin. Palaeontological techniques however inevitably concentrate on details of fragmentary postcranial bones and can benefit from a whole-animal perspective. This can be provided by field studies of locomotor behaviour, which provide a real-world perspective of adaptive context, against which conclusions drawn from palaeontology and comparative osteology may be assessed and honed. Increasingly sophisticated dynamic modelling techniques, validated against experimental data for living animals, offer a different perspective where evolutionary and virtual ablation experiments, impossible for living mammals, may be run in silico, and these can analyse not only the interactions and behaviour of rigid segments but increasingly the effects of compliance, which are of crucial importance in guiding the evolution of an arboreally derived lineage.     

From action to language: comparative perspectives on primate tool use, gesture and the evolution of human language

The papers in this Special Issue examine tool use and manual gestures in primates as a window on the evolution of the human capacity for language. Neurophysiological research has supported the hypothesis of a close association between some aspects of human action organization and of language representation, in both phonology and semantics. Tool use provides an excellent experimental context to investigate analogies between action organization and linguistic syntax. Contributors report and contextualize experimental evidence from monkeys, great apes, humans and fossil hominins, and consider the nature and the extent of overlaps between the neural representations of tool use, manual gestures and linguistic processes.     

The Late Permian herbivore Suminia and the early evolution of arboreality in terrestrial vertebrate ecosystems

Vertebrates have repeatedly filled and partitioned the terrestrial ecosystem, and have been able to occupy new, previously unexplored habitats throughout their history on land. The arboreal ecospace is particularly important in vertebrate evolution because it provides new food resources and protection from large ground-dwelling predators. We investigated the skeletal anatomy of the Late Permian (approx. 260 Ma) herbivorous synapsid Suminia getmanovi and performed a morphometric analysis of the phalangeal proportions of a great variety of extant and extinct terrestrial and arboreal tetrapods to discern locomotor function and habitat preference in fossil taxa, with special reference to Suminia. The postcranial anatomy of Suminia provides the earliest skeletal evidence for prehensile abilities and arboreality in vertebrates, as indicated by its elongate limbs, intrinsic phalangeal proportions, a divergent first digit and potentially prehensile tail. The morphometric analysis further suggests a differentiation between grasping and clinging morphotypes among arboreal vertebrates, the former displaying elongated proximal phalanges and the latter showing an elongation of the penultimate phalanges. The fossil assemblage that includes Suminia demonstrates that arboreality and resource partitioning occurred shortly after the initial establishment of the modern type of terrestrial vertebrate ecosystems, with a large number of primary consumers and few top predators.     

Social learning of a communicative signal in captive chimpanzees

The acquisition of linguistic competency from more experienced social partners is a fundamental aspect of human language. However, there is little evidence that non-human primates learn to use their vocalizations from social partners. Captive chimpanzees (Pan troglodytes) produce idiosyncratic vocal signals that are used intentionally to capture the attention of a human experimenter. Interestingly, not all apes produce these sounds, and it is unclear what factors explain this difference. We tested the hypothesis that these attention-getting (AG) sounds are socially learned via transmission between mothers and their offspring. We assessed 158 chimpanzees to determine if they produced AG sounds. A significant association was found between mother and offspring sound production. This association was attributable to individuals who were raised by their biological mother-as opposed to those raised by humans in a nursery environment. These data support the hypothesis that social learning plays a role in the acquisition and use of communicative vocal signals in chimpanzees.     

Morphological distance between australopithecine,human and ape skulls

This paper attempts to quantify the morphological difference between fossil and living species of hominoids. The comparison is based upon a balanced list of craniodental characters corrected for size (Wood & Chamberlain, 1986). The conclusions are: craniodentally the australopithecine species are a unique and rather uniform group, much nearer to the great apes than to humans; overall, their skull and dentition do not resemble the human more than the chimpanzee’s do.