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

originalsymmetric Hadza Face Preferences Symmetry 5 pairs

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

Macaque Preferences Preferred by females Gaze longer at symmetrical face Symmetry asymsym 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 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