Blue-eyed een erefer blue-eyed women: the role of life history strategies and sociosexuality

Previous research (Laeng et al., 2007) conducted on Norwegian samples showed that blue-eyed men rate blue-eyed women as more attractive, while brown-eyed men and all the women show no differences in attractiveness assessments with respect to eye colour. Correspondingly, positive assortative mating was found for blue, but not brown eyes, and it most often occurred in blue-eyed men. We aimed to replicate this blue-like-blue effect in the Croatian population, which differs in the ratio of eye colour phenotypes (blue eye colour is the most prevalent in Norway while brown is the most prevalent in Croatia). Additionally, we examined whether this effect is moderated by life history strategies and sociosexuality. Our hypothesis was that the effect would be larger in those blue-eyed men who exert a slower life history strategy and who are sociosexually restrictive. One hundred and twenty-eight participants assessed the attractiveness of blue-eyed and brown-eyed models, whose eye colours were experimentally manipulated in such a way that participants were shown models with natural or artificially changed eye colours. The blue-like-blue effect was replicated in the context of preferences, although it was smaller than in the original study. However, unlike the original study, in a sample of 138 participants no assortative pairing by eye colour was found between participants and their romantic partners. Finally, the hypothesis about the moderation was supported for life history strategies, but not for sociosexuality. In addition to the rationale for the blue-like-blue effect based on the paternity uncertainty account, which was offered by the authors of the original study, we discussed other accounts of this phenomenon.

Variation, Consistency, and Reputation

There is typically considerable between-individual variation in trait values in natural populations. Game theory has often ignored this, treating individuals as the same. However, the existence and amount of variation is central to many predictions in biological game theory, as this chapter illustrates. Variation is central to signalling systems and stabilizes these systems as well as extensive-form games. Variation leads to individuals taking a chance that a partner is better than average; for example, promoting cooperation in a finitely repeated Prisoner’s Dilemma game. When there is both variation and within-individual consistency, so that past behaviour is predictive of current behaviour, reputation is important. As is demonstrated, once population members respond to reputation, this then selects for all to modify their behaviour so as to change their reputation and so change how others interact with them in the future, with consequences for the level of cooperation in the population. Furthermore, as a game of trust shows, the extent to which reputation matters can depend on whether individuals are prepared to pay the cost of being socially sensitive, which depends on the amount of variation. Variation selects for individuals to be choosy about their partner, and choosiness can lead to assortative pairing in a population, again promoting cooperation. The importance of choosiness in a market situation is demonstrated by a model in which partners have to decide how much to commit to one another, with factors that enhance choosiness leading to higher levels of commitment.

Assortative pairing by telomere length in King Penguins (Aptenodytes patagonicus) and relationships with breeding success

Telomeres are noncoding genetic repeats protecting the ends of linear chromosomes. Long telomeres are often associated with high individual survival, and interindividual variation in telomere length has recently been proposed as a proxy for individual quality. Therefore, one might expect individuals of either sex with long telomeres to be of higher intrinsic quality and to be preferred in the context of mate choice. Thus, in sexually monomorphic species where individuals discriminate mates on the basis of signals of intrinsic quality, mate choice should lead to assortative pairing by telomere length, and it should be associated with breeding performance. We tested these two predictions in the King Penguin (Aptenodytes patagonicus J.F. Miller, 1778), a sexually monomorphic seabird. Over 3 years of study and 73 penguin pairs under contrasting environmental conditions, we found strong assortative pairing by telomere length. Interestingly, only female telomere length was positively associated to chick survival up to fledging, and this relationship was only apparent when foraging conditions at sea were average. The positive link between telomere length and breeding success confirmed that telomere length is somehow related to individual biological state at a given time. The proximate mechanisms by which birds assess individual state related to telomere length remain to be discovered.