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

• “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

Thornhill, 1992

Non-Human Species Preferences for Symmetry

• Female barn swallows prefer males with symmetrical tail feathers

• Female zebra finches prefer symmetrical males

Møller, 1994, Anim Behav

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)

Symmetry is found attractive…

Original

Symmetric

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?

original symmetric

Hadza Face Preferences Symmetry

5 pairs

original symmetric

Hadza Face Preferences Symmetry

5 pairs

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

Macaque Preferences

Preferred by females

• Gaze longer at symmetrical face

Symmetry

asym sym

Waitt & Little (2006) IJP

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 allSuggests common origin to developmentGood-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