Human Commercial Models’ Eye Colour Shows Negative Frequency-Dependent Selection

Isabela Rodrigues Nogueira Forti,Robert John Young

doi:10.1371/journal.pone.0168458

Abstract

In this study we investigated the eye colour of human commercial models registered in the UK (400 female and 400 male) and Brazil (400 female and 400 male) to test the hypothesis that model eye colour frequency was the result of negative frequency-dependent selection. The eye colours of the models were classified as: blue, brown or intermediate. Chi-square analyses of data for countries separated by sex showed that in the United Kingdom brown eyes and intermediate colours were significantly more frequent than expected in comparison to the general United Kingdom population (P<0.001). In Brazil, the most frequent eye colour brown was significantly less frequent than expected in comparison to the general Brazilian population. These results support the hypothesis that model eye colour is the result of negative frequency-dependent selection. This could be the result of people using eye colour as a marker of genetic diversity and finding rarer eye colours more attractive because of the potential advantage more genetically diverse offspring that could result from such a choice. Eye colour may be important because in comparison to many other physical traits (e.g., hair colour) it is hard to modify, hide or disguise, and it is highly polymorphic.

Highlights

It has been proposed that the variation observed in human eye colour is the result of sexual selection [1]
The diversity of human eye is thought to be the result of selection for rarity or in genetic terms negative frequency dependent selection, this hypothesis has not been tested by quantitative methods
Data were collected on the eye colour of human commercial models from the, publically accessible, on-line sites of model agencies in the United Kingdom (Select Model Management, Elite Models, Models 1 and Storm Management) and in Brazil (Mega Models, L’equipe Agence, Ford Models, Ten Model Management and Joy Management)

Summary

Introduction

It has been proposed that the variation observed in human eye colour is the result of sexual selection [1]. Everyone had brown eyes, and this situation lasted at least until modern humans entered northern Europe some 30,000 years ago. Analysis of DNA from skeletal remains has revealed that blue eyes were already present in humans at Motala, Sweden some 8,000 years ago [2]. A wide range of human eye colours exist they are grouped together in three broad categories brown, blue and intermediate (e.g., green).

Methods

Results

Conclusion