Tuesday, March 8, 2011 | By Callie J. Paar
This question, one of many that all parents hope never to hear from their children regardless of age, is one that author Jared Diamond exposes rather quickly as being not what it seems in his book of the same title. At first thought, one might think that sex is fun because otherwise, who would want to have children? That is the point at which the anthropologist realizes the true depth of this deceptively easy question: after all, passing on genes and producing offspring is the name of the evolutionary game. The more reasonable question to ask is why are all of the players of this game – humans in particular – playing by different rules?
Anthropology teaches us that one cannot be ethnocentric in studying other cultures, and Diamond suggests that we also not be “human-centric,” when it comes to studying our species’ reproductive patterns in comparison with those of other species. This suggestion is for the better, considering how very unusual humans are reproductively.
Why are we so unusual? Human beings tend to live in pair-bonded couples that occupy a larger territory shared by many other pair-bonded couples, co-parenting their offspring – which have the longest period of parental dependence in the natural world. We share our pair-bonded couple behavior with songbirds, who, like humans, often participate in extramarital copulations in order to produce more offspring (males), or produce offspring with better genes (females). No other primates participate in this behavior, either existing in harem or promiscuous mating systems or as mated pairs that have their own territory (as in Gibbons). Songbirds also co-parent their offspring, as neither parent can provide enough for the chicks alone, much the same as in humans. However, songbirds develop faster than human babies, and are out of the nest before most toddlers can even walk. Even chimpanzees, our closest genetic relatives, begin learning to become as self-sufficient as members of a troupe can be once their mothers begin to wean them.
This means that humans are expending a lot of biosynthetic energy when it comes to reproduction. A nine-month pregnancy is nothing compared to the twenty-two month gestation period of elephants, but human offspring must be cared for constantly until at least their teens, when they begin learning to become independent of their parents. This is longer than any other species, and can put biological strain on both parents in addition to the potential of strained resources. And that doesn’t even take into consideration that the child may not biologically be the father’s offspring, in which case the father loses out, having spent his efforts on the genes of a rival male while sacrificing his ability to go produce offspring with other mates.
Humans have a concealed ovulation, meaning that females are not aware of when they are ovulating, which results in sex at any time during our ovarian cycles and fewer offspring. This could be the fundamental reason why we view sex as being fun – we can have it at any time, unlike the vast majority of the rest of the world’s species of animals. There are many theories as to why we evolved in this manner, two of which are complete polar opposites: the daddy-at-home theory of Richard Alexander and Katharine Noonan, and the many-fathers theory of Sarah Hrdy.
The daddy-at-home theory suggests that concealed ovulation evolved as a means of keeping males in the home and creating a co-parent situation; increasing the chances of survival of offspring with little doubt as to paternity, while sacrificing the ability to father more offspring with other females. On the other hand, the many-fathers theory suggests that concealed ovulation would allow a female to mate with all of the males in a group, creating the possibility that any of them could be the father of the resulting child. This would lower aggression in the group among males, and would prevent the possibility of infanticide, since all of the males could be led to believe that they had sired the offspring.
Diamond suggests a mixture of these theories as being evolutionarily correct. He states that humans began in harem reproductive systems, originally with slight ovulatory signs – it would be visible that the woman was ovulating – to make reproduction more efficient. Their ovulation evolved to become concealed to confuse paternity, as in the many-fathers theory, and later their mating systems evolved into monogamy, allowing the concealed ovulation to keep daddy-at-home. After reading this book, I agree with Diamond’s take on concealed ovulation, as his suggestion of the two both being true is presented in a very logical argument that follows what we understand of evolutionary patterns and natural selection.
Additionally, humans are the only species in which females undergo the shutdown of fertility known as menopause, a phenomenon that has been observed in large numbers only in baleen whales, but not universally as in humans. The benefits of menopause far outweigh the costs, including the ability of the postmenopausal woman to provide more for her existing children and grandchildren than for a new baby. Since every new birth creates a higher risk to the survival of the mother and subsequently the infant, menopause is a biological way of helping women to pass on their genes more effectively. It also provides a means of passing on information, knowledge, wisdom, etc;, as in the example of the Rennellese woman who was the only remaining survivor of the hungi kengi cyclone of 1910. Her tribe had a higher chance of surviving another cyclone because of her knowledge than would a tribe without a survivor to pass on the memories.
Finally, human beings advertise their reproductive potential just as much as any other animals on the planet. This is largely in the form of our bodies, with the most honest qualities being muscles and fat in men and women respectively. Men who are muscular in healthy amounts, and women who have fat in healthy amounts, are viewed as being more attractive. A muscular male can defend his mate and children, and is likely to be more physically fit than a less muscular male, while a woman with a healthy amount of fat in her breasts, hips, and buttocks advertises that she will be more capable of birthing, feeding, and probably raising offspring. Since Diamond points out the delicacy of the human face – it is susceptible to most diseases, disorders, etc; – it warrants mentioning that the face tells us not only a little bit about the physical condition of the person, but also – as mentioned in class – how much testosterone or estrogen a person has. Estrogen creates feminine features, such as bigger eyes, lips, and a smaller chin and jaw, while testosterone creates masculine features, such as a broader jaw and larger chin.
So, why is sex fun? Millions of years of evolution have given humans the ability to copulate whenever they want with less risk of offspring, though behaviorally humans tend towards co-parenting so that when offspring do occur, there is less effort on the part of any one parent raising the child that will be with them for over a decade before it begins to fend for itself. There may be some extramarital thrills along the way, or perhaps they will meet someone who advertises qualities that they are attracted to and settle down with them, but I believe that sex is made fun in part because of the evolution it has required to get to this point. After all, if sex weren’t fun, who would want to have children?
Bibliography:
Diamond, Jared. Why is Sex Fun? The Evolution of Human Sexuality. 1st ed. New York: Basic Books, 1997. Print.