The Complexity and Phylogenetic Continuity of Laughter and Smiles in Hominids.

Marina Davila-Ross,Guillaume Dezecache

doi:10.3389/fpsyg.2021.648497

Abstract

Laughter and smiles are often, but not always, associated with positive affect. These expressions of humans help to promote social relationships as well as the development of cognitive and socio-emotional skills and they may have a positive impact on health and well-being, hereby covering a selection of fitness-relevant benefits. Both laughter and smiles of positive affect also occur early in human development and across cultures, suggesting deep roots in human biology. The present work provides an evolutionary reconstruction of the evolution of human laughter and smiles of positive affect in form and function, based on the principle of maximum parsimony. According to the Complexity and Continuity Hypothesis, human laughter and smiles of positive affect must have evolved within the context of play from ancestral species. Furthermore, ancestral ape laughter and their open-mouth faces must already have been complex in form and function and changed over time via categorically different phylogenetic pathways to become characteristic, effective, and pervasive behaviors of everyday social interactions in humans.

Highlights

Laughter and smiles of humans have often been discussed in close association with each other
It is important to be generally cautious when identifying emotional states of individuals based on their behavioral actions (Fridlund and Russell, 2006; Fridlund, 2014; Waller et al, 2017), laughter and smiles are clearly strongly linked to positive emotions in many situations and their corresponding neurochemical changes (Wild et al, 2003; Dunbar et al, 2012; Manninen et al, 2017)
The way playing great apes produce their multimodal and unimodal expressions of play strongly resembles the way playing children produce laughter and open-mouth smiles of positive affect (Rothbart, 1973; Addyman et al, 2018), respectively. Whereas, such basic observations might naturally lead to the notion of phylogenetic continuity from primordial play expressions to human laughter and smiles of positive affect (Darwin, 1872; Redican, 1982), other possible explanations are that laughter and smiles are human-unique behaviors or that they evolved from different primordial expressions

Summary

INTRODUCTION

Laughter and smiles of humans have often been discussed in close association with each other. The way playing great apes produce their multimodal and unimodal expressions of play strongly resembles the way playing children produce laughter and open-mouth smiles of positive affect (Rothbart, 1973; Addyman et al, 2018), respectively Whereas, such basic observations might naturally lead to the notion of phylogenetic continuity from primordial play expressions to human laughter and smiles of positive affect (Darwin, 1872; Redican, 1982), other possible explanations are that laughter and smiles are human-unique behaviors or that they evolved from different primordial expressions (van Hooff, 1972; Preuschoft and van Hooff, 1995). It can be applied for any hard-wired multivariate traits (for primate expressions, see Geissmann, 2002; Davila-Ross and Geissmann, 2007; Davila-Ross et al, 2009)

DISCUSSION

ETHICS STATEMENT