In his limited experience, women so rarely play the role of sexual aggressor that when a woman does, he would be unlikely to turn her down. If she asked for something in return, such as a demonstration of his vaunted hunting skills, he would be eager to comply even if her request entailed considerable hazard. The first libidinous peak in a woman’s monthly cycle, coincident with ovulation, is for the purpose of conception; the second libidinous peak, coincident with menses, is to restore her iron homeostasis.
Another aspect of the human female’s monthly sexual cycle stands out when compared with those of other female mammals. In order for her uterus to shed its lining, a very dramatic sea-change must occur within her hormonal system just prior to the onset of menses, and this ebb tide washes away in a relative instant.
Every major hormone has an effect on both body and the mind; sudden disruptions in the serum levels of any hormone produce profound physiological and psychic phenomena. Anyone who has taken steroidal drugs, such as cortisone, or who knows someone who has taken them, can attest to the profound changes in both appearance and personality that manifest. An examination of the physiological and emotional changes associated with a woman’s period will provide a clearer picture of why human menses was such an extraordinary adaptation.
At the beginning of a new cycle, the interior uterine landscape is sere and appears dead. The remains of a few unshed necrotic cells lie heaped here and there on what has become a vast raw plain following the expulsion of the last menstrual effluvia. Then, with each passing day as ovulation approaches, new cells, like sprouts of fresh grass, begin to appear, forming a resurgent healthy nap. These cells steadily grow taller, forming stalks, and at their extremities, tendrils called “villae” begin to wave gently. What at first resembled new-grown prairie grass quickly becomes a luxuriant rain forest. An exquisitely sequenced orchestration of hormones stimulates this lush uterine growth. The levels of estrogen, the sex hormone, and progesterone, the pregnancy hormone, both ascend a steep curve as the egg’s launch site on the ovary pumps them out in prodigious quantities.
These, in turn, stimulate the growth of the uterine lining. Blood vessels, resembling the root systems of trees, corkscrew and pulse with energy. They grow fat and full as they transport increasing amounts of structural material for the uterine mucosal buildup, which has but one purpose—to be ready if conception occurs. Should a fertilized ovum wander in from either of the two narrow fallopian tubes, it will find itself in a dark wonderland, enveloped by a sumptuous jungle of villae. This nutrient-rich tangle is waiting with inviting tentacles outstretched, eager to embrace a new life.
But Mother Nature is no sentimentalist. Should conception fail to occur, She will survey the now unnecessary field of waving villae with the keen eye of a farmer about to torch a field that had failed to yield its expected harvest. Estrogen and progesterone levels begin to retreat—at first gently, but as the paramenstrum approaches, with increasing acceleration. Hormonal support for the thickened uterine lining withdraws. The once tall, mighty columnar cells that line the surface wilt. And then, just before the onset of menses, a most dramatic event occurs. As if the rug were being pulled out from under the uterine lining, hormonal levels crucial to the whole enterprise plummet precipitously.
This causes the root-system arteries to constrict in a death spasm. What had been gradually decaying now becomes, within minutes, a holocaust for all the cells lining the uterine surface. The uterus becomes a living shell encasing a dead inner core and serves momentarily as its tomb. Then the arteries that were in constriction suddenly go limp, and blood floods into the space directly under the lining. A hematoma, a lake of blood, forms in the space neatly separating the now dead uterine lining from the dense undergrowth of blood vessels. Resembling a dam that can no longer hold back the swollen river behind it, the necrotic uterine lining ruptures; blood and the remains of formerly lush uterine tissue cascade down toward the cervical opening.
Whenever any tissue of any organ dies and remains within the body, toxic substances released by the dead tissue threaten the existence of the entire organism. In other female mammals that do not menstruate, the uterine lining dies gradually in the absence of conception. Toxic substances are released at a rate that the host’s defenses can easily handle. The uterus’s dead lining is reabsorbed into the mammal’s interior, to be broken down into its valuable constituents and recycled.
Too much of the human uterine lining dies too fast for this process to be a viable alternative for Gyna sapiens. The human female (and the handful of other mammals that menstruate) had to evolve an efficient way to rid her body of what will rapidly become a highly toxic mix of pathogenic bacteria and the poisonous byproducts of cellular death. The solution: The cervix, gatekeeper of the uterus, opens; the uterus contracts rhythmically in what are known as menstrual cramps; and the discarded lining, mixed with about four to eight tablespoons of blood, is expelled down toward the vagina. A woman’s period has begun.*
Besides menses’ physical manifestations, a potent psychological component accompanies it.† In her 1997 book, Molecules of Emotion, neuroscientist Candace Pert argued that what we experience as an “emotion” is, in fact, due to the rise or fall in serum concentrations of a particular polypeptide molecule or combination of molecules. Many of these complex molecules are neurotransmitters that carry or inhibit signals across synapses, the short gaps between neurons—serotonin, norepinephrine, and dopamine being among the more familiar neurotransmitters. Those that carry their messages over longer distances are called hormones.
The word “hormone” means “messenger” in Greek. Released into the bloodstream at one site, a hormone carries information to a distant tissue, causing the target tissue to change its state. For example, the hormone thyroxin, produced by the thyroid gland in the neck, circulates throughout the body and regulates the rate of metabolism for nearly every tissue. Too little thyroxin, and cellular functions gradually slow. Fatigue, weight gain, slow speech, and inability to burn glucose properly with insulin produce the clinical symptoms of hypothyroidism. Too much thyroxin, and eyes bug out, body temperature heats up, and the affected person is so agitated he or she can’t sit still.
In the seventeenth century, René Descartes posed a conundrum that was to intrigue generations of philosophers. How, he asked, does matter affect mind, and how does mind affect matter? Where is the interface between ephemeral mind and solid matter that allows thinking ultimately to change matter? Conversely, by what mechanism does matter, impinging on consciousness, change thinking? Dr. Pert, building on the earlier work of Walter Cannon and Hans Selye, answers these questions by bridging the gap between hormones (matter) and emotions (mind), claiming that the one is indistinguishable from the other. A caveat: Any particular individual may manifest a variable response to different hormone levels.
Estrogen, testosterone, and progesterone profoundly affect mood, especially sexual mood. Men and women treated for medical conditions that require the administration of one or the other of these three potent hormones routinely report psychic fluctuations, increased libidinous thoughts, and vivid sexual dreams. If we accept Pert’s premise that, in one sense, emotions are hormones, what, then, is the effect on a woman’s mental disposition of the sudden withdrawal of estrogen and progesterone that occurs premenstrually? When estrogen and progesterone levels perform their monthly sky dive, a woman’s testosterone level rises dramatically, relatively speaking, even though its serum concentration barely changes.*
Relative testosterone rise is the proximate reason some women experience dramatic mood swings, a sharp rise in libido, and increased aggression during their periods. The ultimate evolutionary reason for this protean display is to entice (or coerce) the male to restock Gyna sapiens’ soon-to-be-tapped iron reserves.†
A few women become combative, argumentative, and, in some extreme cases, dangerous at this time in their cycle. Studies reveal that women who have committed violent crimes are statistically more likely to hav
e done the deed during the paramenstrum. In some legal codes, a crime committed by a paramenstrual female is considered to have an extenuating circumstance.12 Examining at autopsy the ovaries of women who had died by their own hand, pathologists ascertained that slightly over half of these suicides occurred during the paramenstrum.13
A man paired with a woman who experiences paramenstrual mood changes soon learns that for a few days of every month he would be prudent to hunker down and batten the hatches. As her testosterone surges (relatively speaking), his levels will drop. A man learns (and if he is young and doesn’t know, he will learn soon enough) that this is the monthly moment when it would be best for him to adopt a conciliatory posture known among men as the “Jell-O Defense.”
Even if he were not motivated to leave his cozy rock shelter, the behavioral manifestations of the paramenstrum would, in some cases, give him an excellent reason to disappear for a few days. “Uh, you know, hon, I think I’ll just gather up my spears, and me and the boys will go see if we can get us some deer, dear.” If he were to calculate it precisely, he would return just before her ovulation, when his mate was in a more loving and receptive mood. If he returned lugging a huge haunch of venison, his mate’s homeostatic mechanism, which urged her to replenish her iron depots by any means available, would have been well served.
Although the male of the human species doesn’t teeter-totter through monthly cycles, his persistently high levels of circulating testosterone constantly roil the waters of his internal milieu, particularly in adolescence. Since there is little opportunity, especially in his early years of manhood, for the sexual release he craves, Natural Selection provided him with a surrogate safety valve—masturbation. Human males masturbate to ejaculation more often, and more intensely, than any other animal.* I shall propose that the male’s masturbatory proclivity is complementary to the female’s anovulatory cycles. Both appear at first glance to be counterevolutionary, sham sexual activities because they never result in offspring.
Besides the futile loss of considerable quantities of perfectly usable proteinrich fluid and sperm, masturbation during ancestral times would likely have been very dangerous. Most animals eat privately and engage in sex publicly. Humans, in contrast, eat publicly and engage in sex privately. It would be fair to assume that young ancestral adolescents whose urges demanded a lowering of their unbearable sexual tension would have sought privacy, too. This meant leaving the safety of an encampment and wandering off to be alone. Lost in the focused attention of the act, the onanist’s normally alert defenses would be markedly diminished, making him a tasty target for any number of predators. There could have been no more humiliating way for a hunter to die than to be devoured by a beast while caught in the act of masturbating. What would have been the evolutionary advantage of having the male engage in this prodigious sexual charade?
Many researchers posit that masturbation is necessary because a male must constantly refresh his supply of sperm in case he gets lucky and finds a receptive female. His sperm, upon entering the Great Hall, might encounter another male’s sperm that had reached the much-desired anteroom first. Since to the fastest and feistiest go the spoils in the race to the ovum, this theory suggests that masturbation serves to maintain a fresh supply of vigorous sperm capable of outswimming the competition—a theory recently bolstered by the discovery that many sperm (called “kamikaze sperm”) function to deter a competitor’s swimmers from reaching the prize.14 By sacrificing themselves so others can outpace the competition, they selflessly forfeit the chance to be the One.
Each month, a woman releases one egg. During that period, a Homo sapiens will produce approximately 3.6 billion sperm. This number is enough to impregnate every single woman of reproductive age alive at present. Recent research has revealed that the ovum does not just sit passively by while all this commotion is going on around her but rather plays an important role in determining which one among her busy crowd of suitors she will permit to merge into her interior.
The Ever-Ready Sperm Theory of masturbation arose from observations of chimpanzee mating. Female chimps in estrus actively solicit males, who patiently queue up, waiting their turn to copulate. Often, the female will mate with a wide assortment of males in a very short time. Lower-ranking males have a chance on both sides of her ovulation, but it is the alpha male who most often occupies her time at the optimal moment.15 Many males copulate, but it is primarily the dominant who propagate.
Field observers clocked one female chimp having sex with eight different males within the space of an hour. Another female holds the record of fifty copulations in one day.16 A female chimp mates on average 138 times with thirteen different males for every infant she births.17 Male chimpanzees have considerably larger testicles relative to their size than do humans. Making great batches of fresh sperm hurriedly is a critical factor in the intense competition.
This commonly accepted account for Homo sapiens’ prodigious propensity to masturbate, however, cannot be the entire story. The fresh-sperm-at-the-ready hypothesis would predict that male chimps would spend a large part of their day masturbating, but they do not. Human males masturbate the most when their prospects of securing sexual intercourse are the slimmest. Even if they convince an adolescent girl to have sex, it’s unlikely that any of their sperm would need to fend off another male’s sperm. Further, if an adolescent’s sperm were to swim upstream all the way to the fallopian tubes, the odds are against its encountering a viable ovum, given the frequency of young females’ anovulatory cycles.
If the selective pressure for frequent masturbation was for the purpose of enhancing sperm competition with other males, then the practice could be expected to be more prevalent in the years when men are really competing for women. Instead, masturbation peaks in the years when access to females is the least likely, and the practice is in decline during the years when male competition for females is at its maximum.
The extraordinary masturbatory frequency of young human males has little to do with sperm competition but much to do with extremely high testosterone levels. It serves the species well to have its young males in a constant state of homeostatic disequilibrium, doggedly trying to deduce what they must do to obtain “the real deal.” The male experiences chronic stress because he cannot satisfy his sexual urges. Masturbation alleviates some, but not all, of that stress.
In the vulgar wordplay of the locker room, young men refer to their penises as their “meat.” A common remark made between high-school boys on a Friday afternoon, usually delivered with a punch to the shoulder and a knowing smirk, is, “Have a good weekend, and remember, don’t let your ‘meat’ loaf.” There are many other slang expressions that link a male’s penis, a woman, and meat. “The meat rack,” the “meat market,” and other terms referring to human mating frequently appear in the vernacular. One might wonder why many a male has conflated in his mind the object of a hunt, his member, a woman, and what he will offer her to entice her to sayYes!
Women acquired an important bargaining chip when they gained partial control over their sexual urges and began to demand that sexual intercourse take place on their terms. Unfortunately, their advantage came with a catch. Women can refuse sex, but they must have iron. Men do not need iron, but they do crave sex. Herein lies the evolutionary secret behind the sudden, dramatic appearance of the bold Homo sapiens hunter.
One major impediment, however, remained to bar the road to success for this redoubtable primate adventurer. The basic primate design is an awkward starting point for building an efficient killing machine. Compared with predators like hawks, lions, jaguars, and crocodiles, Homo sapiens was not a very sleek, swift, or imposing beast. Moreover, he lacked the most basic killer accouterments. Mother Nature had to jury-rig the body plan of a vegetarian, converting it in a jiffy into a carnivore.
This, then, was the problem. Gyna sapiens had dispatched her man to “bring home the bacon,” but Homo sapiens was woefully ill-equipped for the task. To ensure that he would triump
h, she would have to come to his rescue. It is at this important juncture that Gyna sapiens became the heroine in our evolutionary story. She accepted a series of interlocking adaptations that, taken as a whole, represented a nettlesome burden. She had to run this evolutionary gauntlet in order to acquire an incredible gift. And no sooner did she acquire it than she bestowed it on her sons and lovers. Homo sapiens would transform the astounding bounty that Gyna sapiens gave him into the deadliest weapon ever hefted. Her boon allowed him to become the most fearsome, efficient predator the planet had ever known.
Sex and
Time
Part III
The similarity between the periodicity of the moon and the length of human menstrual cycles, in combination with the correlation of the length of human pregnancy as a precise multiple of lunar cycles, seems to be too rich to be mere coincidence.
Chapter 13
Moon/Menses
A good model of human origins should provide a number of hypotheses about our ancestors’ behavior and anatomy that interweave in a sensible way. That is, the model must be both internally and externally consistent. It must explain the origins of those traits that are uniquely human above all else, since other traits that we share with the great apes are likely primitive ones that we possess simply due to a common ancestry.
—Craig Stanford1
Egyptian priests venerate the moon as the Mother of the Universe, having the light that makes plants and animals moist and pregnant.
—Plutarch
Sex, Time, and Power Page 20
