What makes female sexuality even more complex is that it is influenced by hormonal fluctuations in a much stronger fashion than it is for men. As elucidated in other chapters, the menstrual cycle is regulated by the intricate interaction of hormones. This merry- (actually, not-so-merry-) go-round of physiological changes occurring in fertile women sends them onto an emotional roller-coaster affecting several aspects of their well-being, including their body temperature, stress levels, mood, but also their lust. While men have a rather constant level of testosterone in their blood, women sexual hormones ebb and flow throughout the cycle, modulating their sexual interest accordingly. Desire will steadily increase during the second week, culminating right before ovulation occurs, usually on the 14th day of the cycle. At the same time, the simultaneous rise of testosterone (the “sex hormone”) and oestrogen (which also has the property to make females more receptive to lovemaking and is essential for vaginal lubrication) will also contribute to the acceleration of her sex drive. In this regard, studies have shown that the phase of the menstrual cycle affected outfit decisions: For example, the closer a woman is to ovulation, the shorter the skirts and the tighter the blouse she (unconsciously) chooses to wear As this time also corresponds to her peak of fecundity, it demonstrates that Mother Nature did a fine optimisation job when programming the connection between these two factors (fertility and libido) with the objective of multiplication and species-survival.
In the second half of the menstrual cycle, however, a woman’s hunger for sex then fades away as she approaches the infertile period of menstruation. This is mainly due to her ovaries’ production of progesterone during and after ovulation, which partially reverses the effect of testosterone in her system, thus curbing her desire. As the name reveals, this hormone’s role is to precede and to favour gestation by preparing the lining of the womb that will receive and sustain the egg if it becomes fertilised by a sperm (which would result in pregnancy). It is only after the body has detected that the egg is not fertilised that progesterone levels drop again and menstrual bleeding sets in. The emergence of progesterone, therefore, indicates to the female body that the fun is over and that it is now possibly time to take care of the embryo (or imbroglio – depending on how it happened).
As pointed out above, the primary purpose of sex since the origins of times has been to trade genes with someone else in order to create stronger chromosomes in the next generation of babies. Some readers will think that this has not so much to do with emotions either. Why, then, all the fuss about affection, caring, devotion, commitment, many men will ask. Given that men and women now have access to a variety of contraceptive methods, why can’t we stick to the cock and ass and tits and butthole pleasures? Shouldn’t sex be about this rusty trombone, dirty Sanchez, Cincinnati bowtie, and pussy-juice cocktail, and shit-stained balls after all? Do love and connection really have to be part of the sex equation in the 21st century? The answer here could not be clearer: As a general rule, women are still unable to separate emotion from conjugation. For them, love and sex are the two sides of the same coin, one is the consequence of the other, one actually equals the other – at least this is what a vast majority of females claim.
Seldom will a woman admit that an affair “was only about sex” or view intercourse “just as sex”. Instead, what one usually hears are classical formulas like “as an individual I feel I could not have sex except with someone I loved”, or “I have to be feeling very intensely, or in love, or overwhelmed by sexual feelings in order to enter a deep sexual encounter.” These two declarations highlight one very important point: For women, a sexual relationship is not merely a physical activity (as it may be the case for many men), but rather a physical or emotional exchange with a person with whom they have a connection. Therefore, they will always prefer to have a personally close relationship to a casual one. But even girls with a comparatively promiscuous lifestyle tend to insist on a minimum of feelings when fooling around. In a survey among students specifically picked out for their vivid sexual activity, no more than 32 percent of the female respondents disagreed to the statement, “I feel I should be emotionally involved with a woman/man before having sex with him/her”, compared to 72 percent of the men asked.
 See chapters 8 “A woman’s heart is as deep as the ocean” and 28 “Pluck flowers as they bloom; wait and you’ll have only the twigs”.
 Buss (2003), p. 247
 Cited in: Hite (1981), p. 479
 Cited in: Buss (2000), p. 55