Abstract
Variation in methods and measures, resulting in past dispute over the existence of population handedness in nonhuman great apes, has impeded progress into the origins of human right-handedness and how it relates to the human hallmark of language. Pooling evidence from behavioral studies, neuroimaging and neuroanatomy, we evaluate data on manual and cerebral laterality in humans and other apes engaged in a range of manipulative tasks and in gestural communication. A simplistic human/animal partition is no longer tenable, and we review four (nonexclusive) possible drivers for the origin of population-level right-handedness: skilled manipulative activity, as in tool use; communicative gestures; organizational complexity of action, in particular hierarchical structure; and the role of intentionality in goal-directed action. Fully testing these hypotheses will require developmental and evolutionary evidence as well as modern neuroimaging data.
Highlights
Lateralization was present early in vertebrate phylogeny (e.g., MacNeilage et al 2009; Rogers and Andrew 2002) and is even known in invertebrates (e.g., Frasnelli et al 2012), the manifestation of cerebral and functional asymmetries in the form of handedness has been argued to distinguish the human species, notably in connection with hemispheric dominance for language (e.g., Corballis 1991; Knecht et al 2000)
This study showed that the strength of right-handedness for manipulative activities was much greater in adults than that reported in young children, whereas the difference with age was rather slight for pointing gestures. This comparison suggests that the emergence of hand preference in the course of human ontogeny may be driven by communicative gestures, and the later strengthening of right-hand preference for object manipulations may relate to an increasing need to use complex tools (Cochet and Vauclair 2012)
The analysis of manual asymmetries in human and nonhuman primates has provided some answers to the question of whether or not there is a common substrate for language and handedness
Summary
Lateralization was present early in vertebrate phylogeny (e.g., MacNeilage et al 2009; Rogers and Andrew 2002) and is even known in invertebrates (e.g., Frasnelli et al 2012), the manifestation of cerebral and functional asymmetries in the form of handedness has been argued to distinguish the human species, notably in connection with hemispheric dominance for language (e.g., Corballis 1991; Knecht et al 2000). This study showed that the strength of right-handedness for manipulative activities was much greater in adults than that reported in young children, whereas the difference with age was rather slight for pointing gestures This comparison suggests that the emergence of hand preference in the course of human ontogeny may be driven by communicative gestures, and the later strengthening of right-hand preference for object manipulations may relate to an increasing need to use complex tools (Cochet and Vauclair 2012). The common neural responses elicited by tool use and language perception in humans (Higuchi et al 2009) have suggested that Broca’s area may be involved in the processing of structured sequences of elements This ‘hierarchical structure hypothesis’ can explain some discrepancies observed in studies with human adults: Significant correlations have been reported between hemispheric specialization for language and hand preference for manipulative activities, such as flipping a coin and striking a match, but not for other activities (Bryden et al 1994). Hopkins et al suggest that the motor skills associated with throwing have enabled a greater cortical connectivity between primary motor cortex and the Broca’s area homologue during hominid evolution
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