Is human conversation more efficient than chimpanzee grooming? Comparison of clique sizes

Clique sizes for chimpanzee (Pan troglodytes) grooming and for human conver sation are compared in order to test Robin Dunbar's hypothesis that human l anguage is almost three times as efficient a bonding mechanism as primate g rooming. Recalculation of the data provided by Dunbar et al. (1995) reveals that the average clique size for human conversation is 2.72 whereas that o f chimpanzee grooming is shown to be 2.18. The efficiency of human conversa tion and actual chimpanzee grooming over Dunbar's primate grooming model (a lways one-to-one and a one-way interaction) is 1.27 and 1.25, respectively, when we take role alternation into account. Chimpanzees can obtain about t he same efficiency as humans in terms of quantity of social interactions be cause their grooming is often mutual and polyadic.