Evolution of Human-Like Social Grooming Strategies Regarding Richness and Group Size

Masanori Takano,Genki Ichinose

doi:10.3389/fevo.2018.00008

Masanori Takano, Genki Ichinose

Open Access

https://doi.org/10.3389/fevo.2018.00008

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Abstract

Human beings tend to cooperate with close friends, therefore they have to construct strong social relationships to recieve cooperation from others. Therefore they should have acquired their strategies of social relationship construction through an evolutionary process. The behavior of social relationship construction is know as "social grooming." In this paper, we show that there are four classes including a human-like strategy in evolutionary dynamics of social grooming strategies based on an evolutionary game simulation. Social relationship strengths (as measured by frequency of social grooming) often show a much skewed distribution (a power law distribution). It may be due to time costs constraints on social grooming, because the costs are too large to ignore for having many strong social relationships. Evolution of humans' strategies of construction of social relationships may explain the origin of human intelligence based on a social brain hypothesis. We constructed an individual-based model to explore the evolutionary dynamics of social grooming strategies. The model is based on behavior to win over others by strengthening social relationships with cooperators. The results of evolutionary simulations show the four classes of evolutionary dynamics. The results depend on total resources and the ratio of each cooperator's resource to the number of cooperators. One of the four classes is similar to a human strategy, i.e. the strategies based on the Yule--Simon process of power law.

Highlights

Cooperation is common among humans and it is fundamental to our society (Smith and Szathmáry, 2000; Fehr and Fischbacher, 2003)
We aim to show the adaptivity of the social grooming strategies in order to explore the evolution of human social intelligence predicted by the social brain hypothesis
We only focus on the evolution of social grooming strategies while cooperation from gromees’ is static

Summary

Introduction

Cooperation is common among humans and it is fundamental to our society (Smith and Szathmáry, 2000; Fehr and Fischbacher, 2003). The amount of cooperation by other people is limited because they have to pay costs (e.g., money, time, opportunities, food, etc.) (Santos et al, 2006; Xu and Wang, 2015). People carefully choose their friends in order to receive intensive cooperation (Rand et al, 2011; Grujicet al., 2012; Wang et al, 2012). People tend to cooperate with close friends. An experimental study using the Donation Game shows that participants tend to cooperate more with closer friends (Harrison et al, 2011). Another study using the Public Goods Game shows that friend groups are more cooperative with each other than with other groups (Haan et al, 2006). In a data analysis study dealing with the data set of a social network game, people’s frequent communication increases their cooperative behavior (Takano et al, 2016a,b)

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