“Is Beauty Really in the Eye of the Beholder?”

Animal attraction:

some similarities in human and non-human animal mate-choice

Anthony Little

Symmetry in Animals

Preferences for

Symmetry

Non-Human Species Preferences for Symmetry

• Scorpion fly females prefer males with symmetrical bodies

Thornhill, 1992

• “All animals prefer symmetry in their mates. The male Japanese scorpion flies with the most symmetrical wings gets the most mates."

Gil Grissom, CSI, Season 2

Non-Human Species Preferences for

Symmetry

• Female barn swallows prefer males with symmetrical tail feathers

Møller, 1994, Anim Behav

• Female zebra finches prefer symmetrical males

Swaddle & Cuthill, 1994, Nature

Symmetry

• Most features are supposed to be symmetrical

• Deviation from symmetry reflects imperfect development

• Symmetry = a measure of quality

Measuring

Symmetry

Attractiveness ratings of women correlate with measured symmetry

Grammer & Thornhill, 1994, JCP

Penton-Voak et al., 2001, PRSB

Symmetry Manipulation

The lower images are made using the left/right average of the 224 feature points

(only 4 are

Marked here)

Original

Symmetric

Symmetry is found attractive…

Perrett et al., 1999, EHB

Symmetry is More Associated with

Attractiveness in Opposite-Sex Faces

Little et al., 2008, Behavioural Ecology

The Hadza of Tanzania

• Live in small bands

• Hunt with bows and arrows

• Gather roots, tubers and wild fruits

• Conditions representative of human evolution?

Hadza Face Preferences Symmetry

5 pairs original symmetric

Hadza Face Preferences Symmetry

5 pairs original symmetric

Little, Apicella, & Marlowe (2007) Proc Royal Soc

Macaque Preferences Symmetry

Preferred by females asym

• Gaze longer at symmetrical face

Waitt & Little (2006) IJP sym

Relationships between

Sexual Dimorphism and

Symmetry

Measuring

Symmetry &

Sexual dimorphism

Penton-Voak, et al. 2001,

Proc Royal Soc

Hadza, Europeans, & Macaques

 Measured symmetry and masculinity in:

 70 Hadza, 177 European, 123 Macaques

 Males

Hadza, Europeans, & Macaques

 Correlation between S and M in all

 Suggests common origin to development

 Good-genes? Good environment?

Conclusions

• We can examine the importance of certain traits across species:

• Many animals ‘prefer’ symmetric mates

• Facial asymmetry appears linked to other important traits in primates

Conclusions

• There are some broad similarities between humans and other animals…

• Understanding how other animals choose their mates can help us understand behaviour in humans

• ...and vice versa