Current theoretical and empirical findings suggest that mate preferences are mainly cued on visual, vocal and chemical cues that reveal health including developmental health. Beautiful and irresistible features have evolved numerous times in plants and animals due to sexual selection, and such preferences and beauty standards provide evidence for the claim that human beauty and obsession with bodily beauty are mirrored in analogous traits and tendencies throughout the plant and animal kingdoms. Human beauty standards reflect our evolutionary distant and recent past and emphasize the role of health assessment in mate choice as reflected by analyses of the attractiveness of visual characters of the face and the body, but also of vocal and olfactory signals. Although beauty standards may vary between cultures and between times, we show in this review that the underlying selection pressures, which shaped the standards, are the same. Moreover we show that it is not the content of the standards that show evidence of convergence--it is the rules or how we construct beauty ideals that have universalities across cultures. These findings have implications for medical, social and biological sciences.

Traits correlated with male mating success are likely to be subject to sexual selection. Sexually selected characters are thought to be costly to develop and maintain. If males do not vary their investment in sexual traits in relation to their ability to bear the costs, there should be a negative relationship between male longevity or survival and the expression of sexual traits. In particular, a negative relationship is predicted by pure Fisherian models for the evolution of sexual ornaments. The same should also be true for traits that evolve via pleiotropy (e.g., due to sensory exploitation or bias) with no subsequent evolution of condition dependent modification. We collected information on the relationship between traits correlated with male mating rate and estimates of adult male survivorship or life span. In total we obtained 122 samples from 69 studies of 40 species of bird, spider, insect, and fish. In a meta-analysis we calculated the average sample size weighted correlation between trait expression and adult survival. Analyses at the level of samples, studies, and species revealed significant positive relationships (r = 0.08, 0.10, and 0.13, respectively; all P < 0.001). The unweighted correlation at the species level was r = 0.24. In general, males with larger ornaments or weapons, greater body size, or higher rates of courtship showed greater survivorship or longevity. This finding is inconsistent with pure Fisherian models or other models that do not incorporate condition or quality dependent trait expression. It suggests that male investment in sexually selected traits is not fixed but varies in relation to the ability to pay the underlying costs of expressing these characters. Hence, many secondary sexual characters are likely to be condition dependent in their expression.

Both significant positive and negative relationships between the magnitude of research findings (their 'effect size') and their year of publication have been reported in a few areas of biology. These trends have been attributed to Kuhnian paradigm shifts, scientific fads and bias in the choice of study systems. Here we test whether or not these isolated cases reflect a more general trend. We examined the relationship using effect sizes extracted from 44 peer-reviewed meta-analyses covering a wide range of topics in ecological and evolutionary biology. On average, there was a small but significant decline in effect size with year of publication. For the original empirical studies there was also a significant decrease in effect size as sample size increased. However, the effect of year of publication remained even after we controlled for sampling effort. Although these results have several possible explanations, it is suggested that a publication bias against non-significant or weaker findings offers the most parsimonious explanation. As in the medical sciences, non-significant results may take longer to publish and studies with both small sample sizes and non-significant results may be less likely to be published.

Parasite-mediated sexual selection may arise as a consequence of 1) females avoiding mates with directly transmitted parasites, 2) females choosing less-parasitized males that provide parental care of superior quality, or 3) females choosing males with few parasites in order to obtain genes for parasite resistance in their offspring. Studies of specific host-parasite systems and comparative analyses have revealed both supportive and conflicting evidence for these hypotheses. A meta-analysis of the available evidence revealed a negative relationship between parasite load and the expression of male secondary sexual characters. Experimental studies yielded more strongly negative relationships than observations did, and the relationships were more strongly negative for ectoparasites than for endoparasites. There was no significant difference in the magnitude of the negative effect for species with and without male parental care, or between behavioral and morphological secondary sexual characters. There was a significant difference between studies based on host immune function and those based on parasite loads, with stronger effects for measures of immune function, suggesting that the many negative results from previous analyses of parasite-mediated sexual selection may be explained because relatively benign parasites were studied. The multivariate analyses demonstrating strong effect sizes of immune function in relation to the expression of secondary sexual characters, and for species with male parental care as compared to those without, suggest that parasite resistance may be a general determinant of parasite-mediated sexual selection.