Is genetic diversity associated with mating success in humans? Hanne C. Lie a, b, * , Gillian Rhodes a, 1 , Leigh W. Simmons b,1 a School of Psychology, University of Western Australia b Centre for Evolutionary Biology, School of Animal Biology, University of Western Australia article info Article history: Received 2 April 2009 Initial acceptance 26 June 2009 Final acceptance 29 December 2009 Available online 6 February 2010 MS. number: 09-00205R Keywords: genetic diversity heterozygosity human mating success mean d 2 sexual selection Human mating success has been associated with phenotypic characteristics proposed to signal genetic quality. However, whether genetic quality is directly associated with mating success in humans is unknown. Genetic diversity in general, and particularly at genes important for immune functioning within the major histocompatibility complex (MHC), has been associated with individual fitness and opposite-sex preferences for facial appearance, and may therefore be subject to sexual selection in humans. We investigated whether general and/or MHC genetic diversity, measured as microsatellite heterozygosity and standardized mean d 2 , was associated with mating success, defined as number of sexual partners and age of first sex. Both measures of MHC diversity predicted number of sexual partners in females. Females with greater MHC diversity were more successful at obtaining mates than less diverse females. Mating success in males, however, was not significantly associated with any of the genetic diversity measures. These results provide partial support for a role of genetic diversity in human mating success. Ó 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Recent evidence indicates that sexual selection may be acting on a range of phenotypic characteristics in contemporary human populations (Nettle & Clegg 2006; Jokela 2009). Because contra- ceptive use and family planning constrain numbers of offspring in modern societies, number of sexual partners and age of first sex are commonly used as proxy measures of mating success (e.g. see Thornhill & Gangestad 1994; Faurie et al. 2004; Rhodes et al. 2005; Nettle & Clegg 2006; Peters et al. 2008). These measures of mating success have been positively associated with body symmetry (Thornhill & Gangestad 1994), personality and creative ability (Nettle & Clegg 2006), sports performance (Faurie et al. 2004) and facial attractiveness (Rhodes et al. 2005; Peters et al. 2008). It has been argued that phenotypic characteristics are under sexual selection in humans because they signal mate quality, including genetic quality (Thornhill & Gangestad 1993; Rhodes 2006). However, no studies have directly tested whether genetic quality is associated with mating success in humans. Genetic quality may include heterozygosity (or individual genetic diversity) at many loci, or at key loci such as those associated with immune functioning within the major histocompatibility complex (MHC; Thornhill & Gangestad 1993; Brown 1997, 1999). If heterozygosity is under sexual selection, then we predict that heterozygosity should be associated with individual variation in mating success. Provided heterozygosity is associated with fitness, then heterozygous mates should be preferred because such mates could potentially enhance the chooser’s reproductive success directly, through enhanced fertility, reduced risk of contagion, provisioning of quality resources and parental care (Thornhill & Gangestad 1993; Sauermann et al. 2001) and/or indirectly, by producing offspring that are on average more heterozygous (Mitton et al. 1993; Hoffman et al. 2007). There is some evidence that heterozygosity, both in general and at the MHC, is associated with fitness as well as mate preferences in some nonhuman animals. Genome-wide heterozy- gosity has been associated with fitness-related traits, including fertility and reproductive success, in many species (reviewed in Charlesworth & Charlesworth 1987; Keller & Waller 2002; Coltman & Slate 2003; Kempenaers 2007). For example, reduced heterozy- gosity associated with inbreeding predicted reduced sperm quality and smaller testis size in male wild rabbits, Oryctolagus cuniculus (Gage et al. 2006), while increased heterozygosity was associated with increased reproductive success in both male and female mandrills, Mandrillus sphinx (Charpentier et al. 2005). Heterozy- gosity within the MHC (or human leukocyte antigen, HLA in humans) should be especially advantageous for an individual’s fitness. Because each MHC allele can only detect a restricted range of pathogens, MHC heterozygotes should be able to detect, and thereby initiate an immune response towards, a broader range of * Correspondence: H. C. Lie, Department of Behavioral Sciences, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Norway, P. O. Box 1111 Blindern, 0317 Oslo, Norway. E-mail address: h.c.lie@medisin.uio.no (H.C. Lie). 1 G. Rhodes and L. W. Simmons are at the School of Psychology (M304), Univer- sity of Western Australia, 35 Stirling HWY, Crawley, WA 6009, Australia. Contents lists available at ScienceDirect Animal Behaviour journal homepage: www.elsevier.com/locate/anbehav 0003-3472/$38.00 Ó 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.anbehav.2009.12.040 Animal Behaviour 79 (2010) 903–909