Ethics and Altruism Journal of Anthropological Sciences
Vol. 85 (2007), pp. 235-236
Grooming, coalitions, and reciprocal altruism in primates
Istituto di Scienze e Tecnologie della Cognizione, Consiglio Nazionale delle Ricerche, Roma
The study of primate altruistic behaviours Preliminary meta-analytical data also show
can help to shed light on the evolution of that primates reciprocate amount of grooming
human altruism. In particular, as it provides received, that is they groom their group mates
information on patterns of altruism in species in relation to the grooming received, and that
that may lack advanced cognitive abilities such the degree of grooming reciprocation is inversely
as the capacity for empathy and score-keeping. related to the tendency to direct grooming up
Grooming and agonistic coalitions represent the hierarchy (Schino & Aureli, in preparation).
two traditional examples of primate reciprocal Knowledge of these general patterns
altruism (Trivers, 1971). Seyfarth (1977) of grooming distribution among primates
developed an inﬂuential theoretical model to is to be complemented with an improved
explain the distribution of grooming among understanding of the proximate mechanisms
female primates. This model assumed females underlying reciprocal exchanges. Recent data on
compete for accessing and grooming high-ranking the temporal relations between grooming and
group mates in order to exchange grooming for agonistic support in Japanese macaques (Schino
later support during aggressive confrontations. et al., 2007) suggest reciprocal exchanges are not
Despite its enormous inﬂuence on the based on a short-term temporal contingency,
ethological literature, data supporting Seyfarth's but much more detailed data are needed on this
model were until recently scantier than generally topic. As for the cognitive basis of reciprocation,
assumed. In the last few years, meta-analytical at the moment, both emotion-based and
techniques have been applied to published data cognition-based proximate mechanisms
on primate grooming and agonistic coalitions, have been proposed (Brosnan & de Waal,
and have shown that primate grooming does 2002), but their relative prevalence is unclear.
satisfy most of the assumptions and predictions The data reviewed above highlight that
of Seyfarth's model (Schino, 2001; 2007). nonhuman primates show a variety of altruistic
Primates direct their grooming preferentially to behaviours whose evolution is likely to be based,
higher-ranking animals and, as a results, high- beside kin selection, on the selective mechanism
ranking animals receive overall more grooming initially identiﬁed by Robert Trivers (1971), that
than their lower-ranking group mates. Primates is, reciprocal altruism. These altruistic behaviours
also compete for accessing high-ranking group are deployed strategically among group members
mates, as shown by the signiﬁcant relation in order to maximize received return beneﬁts.
between the groomer's rank and its ability to These observations are relevant to the evolution
distribute grooming in relation to the recipient's of our own species as they provide both
rank. This preference for grooming high- evidence that altruistic behaviour predates the
ranking group mates is explained, as originally evolution of human-like cognitive abilities, and
assumed by Seyfarth's model, by the exchange support to the notion that the need to navigate
that occur between grooming and rank-related a complex social environment favoured the
beneﬁts, for example agonistic coalitions. initial evolution of improved cognitive abilities.
the JASs is published by the Istituto Italiano di Antropologia www.isita-org.com
236 JASs forum: Ethics, Altruism and Evolution
References Schino G., Polizzi di Sorrentino E. & Tiddi B.
2007. Grooming and coalitions in Japanese
Brosnan, S.F., de Waal. F.B.M. 2002. A proximate macaques (Macaca fuscata): partner choice
perspective on reciprocal altruism. Human and the time frame of reciprocation. J. Comp.
Nature, 13: 129-152. Psychol., 121: 181-188.
Schino G. 2001. Grooming, competition and Seyfarth R.M. 1977. A model of social grooming
social rank among female primates: a meta- among adult female monkeys. J. Theor. Biol.,
analysis. Anim. Behav., 62: 265-271. 65: 671-698.
Schino G. 2007. Grooming and agonistic Trivers R.L. 1971. The evolution of reciprocal
support: a meta-analysis of primate reciprocal altruism. Q. Rev. Biol., 46: 35-57.
altruism. Behav. Ecol., 18: 115–120.