When is bigger better? The effects of group size on the evolution of helping behaviours.


Autoria(s): Powers, Simon T; Lehmann, Laurent
Data(s)

11/02/2016

Resumo

Understanding the evolution of sociality in humans and other species requires understanding how selection on social behaviour varies with group size. However, the effects of group size are frequently obscured in the theoretical literature, which often makes assumptions that are at odds with empirical findings. In particular, mechanisms are suggested as supporting large-scale cooperation when they would in fact rapidly become ineffective with increasing group size. Here we review the literature on the evolution of helping behaviours (cooperation and altruism), and frame it using a simple synthetic model that allows us to delineate how the three main components of the selection pressure on helping must vary with increasing group size. The first component is the marginal benefit of helping to group members, which determines both direct fitness benefits to the actor and indirect fitness benefits to recipients. While this is often assumed to be independent of group size, marginal benefits are in practice likely to be maximal at intermediate group sizes for many types of collective action problems, and will eventually become very small in large groups due to the law of decreasing returns. The second component is the response of social partners on the past play of an actor, which underlies conditional behaviour under repeated social interactions. We argue that under realistic conditions on the transmission of information in a population, this response on past play decreases rapidly with increasing group size so that reciprocity alone (whether direct, indirect, or generalised) cannot sustain cooperation in very large groups. The final component is the relatedness between actor and recipient, which, according to the rules of inheritance, again decreases rapidly with increasing group size. These results explain why helping behaviours in very large social groups are limited to cases where the number of reproducing individuals is small, as in social insects, or where there are social institutions that can promote (possibly through sanctioning) large-scale cooperation, as in human societies. Finally, we discuss how individually devised institutions can foster the transition from small-scale to large-scale cooperative groups in human evolution.

Formato

application/pdf

other

Identificador

http://researchrepository.napier.ac.uk/10341/1/PowersLehmann2016b.pdf

http://researchrepository.napier.ac.uk/10341/2/Powers2016b%20Acceptance%20letter%20and%20deposit%20for%20journal%20manuscript.msg

Powers, Simon T and Lehmann, Laurent (2016) When is bigger better? The effects of group size on the evolution of helping behaviours. Biological Reviews. n/a-n/a. ISSN 1464 7931 (In Press)

Idioma(s)

en

en

Publicador

Wiley

Relação

http://researchrepository.napier.ac.uk/10341/

http://dx.doi.org/10.1111/brv.12260

doi:10.1111/brv.12260

Palavras-Chave #HV Social pathology. Social and public welfare #QA75 Electronic computers. Computer science
Tipo

Article

PeerReviewed