Environmental determinants of object manipulation by chacma baboons (Papio ursinus) in two southern African environments

Well-digging in a community of forest-living wild East African chimpanzees (Pan troglodytes schweinfurthii)

Access to resources shapes species' physiology and behaviour. Water is not typically considered a limiting resource for rainforest-living chimpanzees; however, several savannah and savannah-woodland communities show behavioural adaptations to limited water. Here, we provide a first report of habitual well-digging in a rainforest-living group of East African chimpanzees (Pan troglodytes schweinfurthii) and suggest that it may have been imported into the community's behavioural repertoire by an immigrant female. We describe the presence and frequency of well-digging and related behaviour, and suggest that its subsequent spread in the group may have involved some degree of social learning. We highlight that subsurface water is a concealed resource, and that the limited spread of well-digging in the group may highlight the cognitive, rather than physical, challenges it presents in a rainforest environment.

A developmental model for the evolution of language and intelligence in early hominids

This paper presents a model for the nature and adaptive significance of intelligence and language in early hominids based on comparative developmental, ecological, and neurological data. We propose that the common ancestor of the great apes and man displayed rudimentary forms of late sensorimotor and early preoperational intelligence similar to that of one- to four-year-old children. These abilities arose as adaptations for extractive foraging with tools, which requires a long postweaning apprenticeship. They were elaborated in the first hominids with the shift to primary dependence on this feeding strategy. These first hominids evolved a protolanguage, similar to that of two-year-old human children, with which they could describe the nature and location of food and request help in obtaining it. The descendents of the first hominids displayed intuitive intelligence, similar to that of four- to seven-year-old children, which arose as an adaptation for complex hunting involving aimed-missile throwing, stone-tool manufacture, animal butchery, food division, and shelter construction. The comparative developmental and paleontological data are consistent with the hypothesis that the stages of development of intelligence and language and their neural substrates in our species recapitulate the stages of their evolution.

Does play matter? Functional and evolutionary aspects of animal and human play

In this paper I suggest that play is a distinctive behavioural category whose adaptive significance calls for explanation. Play primarily affords juveniles practice toward the exercise of later skills. Its benefits exceed its costs when sufficient practice would otherwise be unlikely or unsafe, as is particularly true with physical skills and socially competitive ones. Manipulative play with objects is a byproduct of increased intelligence, specifically selected for only in a few advanced primates, notably the chimpanzee.

The adaptiveness of play in pongid evolution is traced through the probable changes in selective pressures that occurred in hominid evolution. It is argued that fantasy was an emergent property in hominids, made possible by symbolic intelligence and language, and serving to make play complex enough to continue to provide useful practice for increasingly complex later skills.

The advent of organised instruction and education has meant that play's unplanned, intrinisic goal-setting could be replaced by extrinsic goal-setting in the systematic development of particular skills. However, the need to ensure adequate motivation has continued to give play educational value. In addition, its capacity to enhance innovative behaviour seems to be a residual function of play which has acquired a new cultural importance.

Spontaneous tool use and sensorimotor intelligence in Cebus compared with other monkeys and apes

Spontaneous tool use and sensorimotor intelligence in Cebus were observed to determine whether tool use is discovered fortuitously and learned by trial-and-error or, rather, whether advanced sensorimotor abilities (experimentation and insight) are critical in its ontogeny and evolution.

Etho-archaeology of manual laterality: well digging by wild chimpanzees

We present the first indirect test of manually lateralized behaviour in non-human primates, based on wells dug for drinking water by wild chimpanzees (Pan troglodytes schweinfurthii). Apes at Toro-Semliki Wildlife Reserve, in Uganda, dig bimanually in sandy riverbeds, leaving behind paired piles of excavated sand. The volumes of left- versus right-side piles do not differ, suggesting a lack of behavioural laterality, but this needs to be verified by further, direct observational data.