A quick look in this "how to" section will reveal a veritable cornucopia of guides about why men and women do various things, or the precise mechanics of foreplay, or even how to "get laid" if you're a geeky guy.
A quick look in this "how to" section will reveal a veritable cornucopia of guides about why men and women do various things, or the precise mechanics of foreplay, or even how to "get laid" if you're a geeky guy. These can all be useful, but there's a tremendous amount of subjectivity involved in these discourses. The purpose of this rather brief essay is to disseminate a more scientific understanding of both male and female sexuality in terms of evolutionary biology.
Before we delve into men and women, we must first understand the rather simple mechanism of natural selection. The genetic imperative is a simple one: replication. In a world of limited size/resources, which is commonly referred to as a "Malthusian world," those able to produce the best/most/best equipped progeny, survive and are "selected" by overwhelming the less advantaged. As Richard Dawkins eloquently demonstrated in The Selfish Gene , complex organisms are akin to highly developed vehicles for Genes, and specifically serve their single imperative. Humans are unique in their capacity to cooperate with non-kin members of the same species, however we are still essentially the same sorts of vehicles as other organisms.
The only other prerequisite for approaching human sexual behavior in terms of biology, is understanding the separation of proximal and ultimate causation. Proximal causes can be understood as emotional drives or feelings. Ultimate causation is the logic underlying these urges. The latter is what we will examine here.
Now, onto the topic at hand: human sexuality.
Males are simple creatures (in terms of sexuality). Facial hair appears to be one of the most prominent sexually selected physical attributes particular to men. The human penis and testes are both relatively large (in relation to our body mass) compared to other primates.
The size of the human penis is directly correlated to the size of the human vagina, which is necessarily large to accommodate birthing a child who has gestated for 9 months and has a fucking big skull. The shape of the human penis creates a squeegee-like effect with repeated thrusting (this, in conjunction with examples to follow, has been understood to function as a means of removing competing sperm from other males that may reside in a woman's vagina and within the cervical cavity, which indicates early humans were likely adapted to promiscuous mating).
The large testes of the human male (relative to the rather small testes of our close relative the gorilla) are capable of producing hundreds of millions of sperm. Empirical studies (see Sperm Wars ) have demonstrated that men unconsciously control the amount of sperm they ejaculate based on the probability of the presence of other competing sperm in the female, as well as based on the amount of time that has past since they last copulated with the given female, maxing out on average at about 600 million sperm.
Another point of interest supporting the promiscuous mating hypothesis, is known as the "Coolidge effect." It turns out that the human male (along with a myriad of other mammals adapted to promiscuous mating) is capable of performing sexually multiple times in a row, without the assistance of Viagra, under certain circumstances. The first circumstance occurs when a male is presented with the opportunity to fertilize multiple different women. The second occurs when another male is present, and the second male releases sperm into the female in question after the first. In this case, as long as the first male is conscious of this activity, he will be able to once again perform sexually, and inject additional sperm into the female.
Females are a tad more complex than males, in a sexual sense. The most prominent sexually selected attribute women exhibit appears to be breasts (while other primates have breasts, most of them tend to physically morph into features indistinguishable from their male counterparts when not in the stage of nursing children). As a result of the long gestation and weaning period of human offspring, females are far more selective when it comes to sex.
They also exhibit an interesting attribute that is seen in some (but not all) of the other great apes. This attribute is called occult ovulation. It basically means that the human female is highly skilled at hiding (not only from males, but her own conscious mind) the exact times at which her body will be capable of fertilization. This attribute helps the female obscure paternity from males, and in conjunction with other factors, allows her to more actively select paternity for her offspring from sexual partners.
Another fascinating, though not entirely explainable phenomenon is called cervical tenting. Cervical tenting occurs when a woman achieves orgasm. At that point, the cervical opening assumes a shape that looks a bit like an elephant trunk, and functions as a straw, and with each contraction it angles down into the vagina and sucks up either vaginal fluid (which is acidic and, once incorporated into the cervical mucus, will reduce the likelihood of fertilization) or, if it present, sperm (increasing the chances of fertilization).
Men, who in promiscuous situations have only nominal assurance of paternity, and have little invested in child bearing, have a tendency to mate with as many females as possible (in order to assure maximum replication of their genes). Monogamous situations, which seem to occur as humans achieve longer lifespans, change this formula a bit, as paternity is more clearly assured, and the male has more to gain by investing resources into his progeny. In such situations the male becomes more heavily invested in child rearing, and less inclined to engage in promiscuous behavior (though one would expect vestigial urges to remain).
Females are assured of genetic relatedness to their offspring, regardless of the sexual conventions of her culture. As previously mentioned, long periods of gestation combined with protracted periods of nursing make the female highly invested in selecting the proper male to father her offspring. Highly promiscuous societies like the Canela appear to obscure paternity in an effort to build social cohesion and discourage infanticidal urges and the like. In monogamous societies, the female still has motivation to "cheat." This urge is demonstrated in many other animals including certain birds previously assumed to be monagmous, that frequently "cheat," when possible, to procure superior sperm for fertilization. The logic behind this motivation is rooted in the female's guaranteed genetic relatedness. In either monogamous or promiscuous situations, the female's optimal strategy is to attempt to find the best possible sperm donor, in conjunction with the best possible provider (not necessarily the same individuals) to support her family.
Putting moral judgments aside, it is important to realize the causation of our various urges. Ultimate "happiness", inasmuch as happiness is defined as satiating all of one's desires, is rarely achieved. In both promiscuous and monogamous societies various natural urges are suppressed. In the former type of society, jealousy is "evil" and is punished as such. In the latter type, promiscuity is "evil" and likewise punished. Obviously there are individuals able to transcend cultural limitations in either case, but these are exceptions to the rule. What is important to understand here is that these proximal urges are rooted in a single, logical genetic imperative. This seems rather simple, but it has dramatic implications when it comes to morality.