Facial morphology predicts male fitness and rank but not survival in Second World War Finnish soldiers

John Loehr,Robert B O'Hara

doi:10.1098/rsbl.2013.0049

Abstract

We investigated fitness, military rank and survival of facial phenotypes in large-scale warfare using 795 Finnish soldiers who fought in the Winter War (1939–1940). We measured facial width-to-height ratio—a trait known to predict aggressive behaviour in males—and assessed whether facial morphology could predict survival, lifetime reproductive success (LRS) and social status. We found no difference in survival along the phenotypic gradient, however, wider-faced individuals had greater LRS, but achieved a lower military rank.

Highlights

A constant feature throughout human evolution has been intraspecific conflict [1,2,3], and simulations have identified warfare as a possible major component of human social evolution [2]
Research has demonstrated that male facial morphology can predict social dominance [6], sexual attractiveness [7,8], reproductive success [9,10], testosterone levels [11] as well as strength and fighting ability [12]
As fWHR appears to reflect aggressiveness [14,15,16,20], our finding that lifetime reproductive success (LRS) increases with facial width is in agreement with evidence that aggression is a sexually selected trait [28]

Summary

Introduction

A constant feature throughout human evolution has been intraspecific conflict [1,2,3], and simulations have identified warfare as a possible major component of human social evolution [2]. Aggressive individuals who have participated in small-scale warfare and revenge killings may receive fitness costs [4] or benefits [5]. While these two previous studies allow some inferences to be made about small-scale tribal warfare, little is known of the survival and fitness benefits for individuals in large-scale conflicts. Research has demonstrated that male facial morphology can predict social dominance [6], sexual attractiveness [7,8], reproductive success [9,10], testosterone levels [11] as well as strength and fighting ability [12]. Wider-faced males exploit trust more often, and others tend to trust thinner-faced males more readily [18,19], in the presence of competition, wider-faced males have been shown to demonstrate greater cooperation with peers [17]

Methods

Results

Conclusion