immune system components. Females find the body odor of those males attractive, whose immuno-histo-compatibility complex is highly variable to their own. In this case attractiveness of body odor leads to highly variable heterozygotic offspring. Moreover, as suggested by Karl Grammer, an important possible function of a pheromone would be the induction of affects, because emotions may change information processing in the receiver. Via a pathway to the limbic areas of the brain, the chemical signals carried by odors have a direct influence on emotions. Odors induce negative or positive moods and feelings. Indeed, odors modify the social perception of other persons. Female pheromones. In their vaginal secretions female produce a sample of fatty acids, which are called copulins. Richard Michael and colleagues in Rhesus monkeys have discovered them. Rhesus males show no interest in ovariectomised rhesus females, presumably because ovariectomised rhesus females lose the odor characteristic of ovulation. Rhesus males regain interest in copulation when the vaginal secretions from non-ovariectomised females are applied to ovariectomise females. Studies on menstrual cycle fluctuations in the fatty-acid composition of women's vaginal fluids indicated that a similar type of signaling system might also exist in humans. Human vaginal secretions have a composition that is similar to the vaginal secretions of female rhesus monkeys. Copulins and male perception of females. Astrid Juette and colleagues tested the effect of copulins on male perception of female attractiveness. Interestingly copulins caused over all more positive ratings of females than control. But the effect is graduated: a woman that is rated without smell as very attractive gains less through smell than an unattractive-rated woman does. The less attractive a woman the more she gains through the additional information of her natural smell that a man receiv...
