Hunter-Gatherer Children's Object Play and Tool Use: An Ethnohistorical Analysis

Far from the walking pace. Ecological and evolutionary consequences of the suboptimal locomotion speeds in non-adult humans

INTRODUCTION

Locomotion activities are part of most human daily tasks and are the basis for subsistence activities, particularly for hunter-gatherers. Therefore, differences in speed walking-related variables may have an effect, not only on the mobility of the group, but also on its composition. Some anthropometric parameters related to body length could affect walking speed-related variables and contribute to different human behaviors. However, there is currently little information on the influence of these parameters in nonadult individuals.

METHODS

Overall, 11 females and 17 male child/adolescents, 8-17 years of age, volunteered to participate in this cross-sectional study. Five different pace walking tests were performed on a treadmill to calculate the optimal locomotion speed (OLS) and U-shaped relationship between the walking energy expenditure and speed (χ2 cost of transport [CoT]) (i.e., energetic walking flexibility).

RESULTS

The mean OLS was 3.05 ± 0.13 miles per hour (mph), with no differences between sexes. Similarly, there were no sex differences in walking flexibility according to the χ2 CoT. Body height (p < .0001) and femur length (p < .001) were positively correlated with χ2 CoT; however, female child/adolescents mitigated the effect of height and femur length when walking at suboptimal speeds.

CONCLUSION

Consistent with prior observations in adults, our findings suggest that anthropometric parameters related to body stature are associated with reduced suboptimal walking flexibility in children and adolescents. Taken together, these results suggest that children and adolescents can adapt their pace to the one of taller individuals without a highly energetic penalty, but this flexibility decreases with increasing body size.

A tool to act blind? Object-assisted eye-covering as a self-handicapping behavior and social play signal in Balinese long-tailed macaques

Self-handicapping behaviors evolved as honest signals that reliably reflect the quality of their performers. In playful activities, self-handicapping is described as intentionally and unnecessarily putting oneself into disadvantageous positions and situations. Self-handicapping during play may allow individuals to learn to cope with unexpected events by improving sensori-motor coordination, as well as function as a play solicitation signal. One such self-handicapping behavior involves moving about while deliberately covering one's eyes. We conducted a quantitative study of object-assisted eye-covering (OAEC) in a population of free-ranging Balinese macaques. After evaluating the frequency, form, distribution, and context of OAEC, we measured the responses this behavior elicited (1) in the performers with a focus on sensori-motor self-handicapping, and (2) in their conspecifics, with an emphasis on whether, and if so how, OAEC may facilitate social play. Our data provided some support for several hypotheses: OAEC is a sensori-motor self-handicapping behavior, an attention-getting cue, a social play signal, and a socially self-handicapping tactic during social play. We discuss our results from the perspective of tool-assisted self-handicapping behavior, propose a scenario to account for the emergence of this behavioral innovation, and speculate on the cultural nature of OAEC.

Owl-like plaques of the Copper Age and the involvement of children

In the Copper Age, slate engraved plaques were produced massively in the southwestern corner of the Iberian Peninsula. Researchers have speculated about the function of these palm-sized stone objects for more than a century, although most have favored the idea that they represented goddesses, and served ritual purposes. The plaques are engraved with different designs of varying complexity. In some of them, the ones sporting two large frontal eyes, we clearly see owls modelled after two species present in the area: the little owl (Athene noctua), and the long-eared owl (Asio otus). These two species, living in semi-open habitats, were possibly the most abundant owls around the human settlements and surrounding cultivated fields of the Chalcolithic period. People must have been aware of the owl presence and possibly interacted with them. Why owls but no other animals have been the models may relate to the fact they are the most anthropomorphic of all animals, with large frontally-placed eyes in their enormous heads. In the iconography, owls are systematically represented, even today, with their two eyes staring at the observer, as opposed to the lateral view used for any other animal. Additionally, slate is one of the commonest surface rocks in southwestern Iberia, and it provides a blank canvas for engraving lines using pointed tools made of flint, quartz or copper. The way slates exfoliate makes easy to craft owl-looking plaques. To silhouette animals other than owls in a recognizable way would request extra carving abilities and specific tools. Plaque manufacture and design were simple and did not demand high skills nor intensive labor as demonstrated in replication experiments. Owl engravings could have been executed by youngsters, as they resemble owls painted today by elementary school students. This also suggests that schematic drawings are universal and timeless. We propose that the owl-like slate plaques are the remains of a set of objects used in both playful activities and in ritual ceremonies. The actual engraving of the plaques may have been part of the game. Owlish slate plaques were often perforated twice at the top. We interpret this as insertion points for actual bird feathers added to the plaques, right at the place where tufts emerge in live owls. The frontier among play and ritual is diffuse in liminal societies and there is no contradiction in playing with animal-like toys and, at some point, using them as offerings as part of community rituals related, for instance, to the colossal megalithic tombs so characteristic of the Copper Age.