large. The median 31-year-old male user searches for women aged 22-to-35, while the median 42-year-old male searches for women 27-to-45. The age skew is even greater with messages to other users; the median 30-year-old male messages teenage girls as often as women his own age, while mostly ignoring women a few years older than him. Excluding the 10% most and 10% least beautiful women, women's attractiveness does not change between 18 and 40. If extremes are included, however, "there's no doubt that younger [women] are more physically attractive – indeed in many ways beauty and youth are inextricable. That's why most of the models you see in magazines are teenagers". Pheromones (detected by female hormone markers) reflects female fertility and the reproductive value mean. As females age, the estrogen-to-androgen production ratio changes and results in female faces to appear more and more masculine (thus appearing less "attractive"). In a small (n=148) study performed in the United States, using male college students at one university, the mean age expressed as ideal for a wife was found to be 16.87 years old, while 17.76 was the mean ideal age for a brief sexual encounter. However, the study sets up a framework where "taboos against sex with young girls" are purposely diminished, and biased their sample by removing any participant over the age of 30, with a mean participant age of 19.83. In a study of penile tumescence, men were found most aroused by pictures of young adult females. Signals of fertility in women are often also seen as signals of youth. The evolutionary perspective proposes the idea that when it comes to sexual reproduction, the minimal parental investment required by men gives them the ability and want to simply reproduce 'as much as possible.' It therefore makes sense that men are attracted to the features in women which signal youthfulness, and thus fertility. Their chances of reproductive success are much higher than they would be should they pick someone older—and therefore less fertile. This may explain why combating age declines in attractiveness occurs from a younger age in women than in men. For example, the removal of one's body hair is considered a very feminine thing to do. This can be explained by the fact that aging results in raised levels of testosterone and thus, body hair growth. Shaving reverts one's appearance to a more youthful stage and although this may not