Complex tasks force hand laterality and technological behaviour in naturalistically housed chimpanzees: inferences in hominin evolution.

M Mosquera,N Geribàs,M Llorente,D Riba,A Bargalló

doi:10.1100/2012/514809

Abstract

Clear hand laterality patterns in humans are widely accepted. However, humans only elicit a significant hand laterality pattern when performing complementary role differentiation (CRD) tasks. Meanwhile, hand laterality in chimpanzees is weaker and controversial. Here we have reevaluated our results on hand laterality in chimpanzees housed in naturalistic environments at Fundació Mona (Spain) and Chimfunshi Wild Orphanage (Zambia). Our results show that the difference between hand laterality in humans and chimpanzees is not as great as once thought. Furthermore, we found a link between hand laterality and task complexity and also an even more interesting connection: CRD tasks elicited not only the hand laterality but also the use of tools. This paper aims to turn attention to the importance of this threefold connection in human evolution: the link between CRD tasks, hand laterality, and tool use, which has important evolutionary implications that may explain the development of complex behaviour in early hominins.

Highlights

Hand laterality is a cognitive factor according to which a group of individuals differentially use one hand to perform a task [1] or a group of tasks [2]
We found a link between hand laterality and task complexity and an even more interesting connection: complementary role differentiation (CRD) tasks elicited the hand laterality and the use of tools
This paper aims to turn attention to the importance of this threefold connection in human evolution: the link between CRD tasks, hand laterality, and tool use, which has important evolutionary implications that may explain the development of complex behaviour in early hominins

Summary

Introduction

Hand laterality is a cognitive factor according to which a group of individuals (populations or species) differentially use one hand (left or right) to perform a task [1] or a group of tasks [2]. From a behavioural point of view, the importance of hand laterality lies in the fact that in humans it is the most developed functional asymmetry. Hand laterality seems to be an indicator of brain hemispheric specialisation, which is not exclusive to humans. It is present in species such as rats (Rattus norvegicus) [3], elephants (Elephas maximus) [4], humpback whales (Megaptera novaeangliae) [5], and crows (Corvus macrorhynchos) [6]. Rogers [7] suggests that all vertebrates share brain hemispheric specialisation. Brain hemispheric specialisation seems to be related in humans to linguistic functions. Its pattern of emergence and development throughout human evolution can provide insight into the evolution of human cognitive capacities

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