Division of labour: A democratic approach towards understanding manual asymmetries in non-human primates

A consequence of the ‘gold rush’-like hunch for human-like handedness in non-human primates has been that researchers have been continually analysing observa-tions at the level of the population, ignoring the analy-sis at the level of an individual and, consequently, have potentially missed revelations on the forms and functions of manual asymmetries. Recently, consecu-tive studies on manual asymmetries in bonnet ma-caques, Macaca radiata revealed both the functional and adaptive significance of manual asymmetries res-pectively, and pointed towards the division of labour as being the general principle underlying the observed hand-usage patterns. We review the studies on manual asymmetries in capuchin monkeys, Cebus spp.and argue that the observed hand-usage patterns might re-flect specialization of the two hands for accomplishing tasks that require different dexterity types (i.e. manoeuvring in three-dimensional space or physical strength). To this end, we do a step-by-step analysis of the various tasks used in the studies on manual asymmetries in capuchin monkeys. We then describe the division of labour as a general principle underlyingmanual asymmetries in non-human primates and pro-pose experimental designs that would elaborate the forms and functions of manual asymmetries in non-human primates and the associated adaptive value