The human female became the first female to override her instinctual sex drive and gain the power to refuse sex when she ovulated.
In Georges Lacombe’s wooden bas relief Isis, 1895, the artist depicted the fluid issuing from the woman’s breasts the color of blood. He uncannily portrayed one of the six major pathways a human female can lose the vital mineral iron.
Chapter 3
Red Blood/White Milk
Child raising is the first industry of every species, and if that industry fails, then the species becomes extinct.
—Sir Arthur Keith1
The social relations of all mammals are determined primarily by the physiology of reproduction.
—Sir Zolly Zuckerman2
In Genesis, the Serpent, a reptile, hisses into Eve’s ear how she might acquire self-awareness and escape from her reptilian brain. She, not Adam, takes the first bite of the forbidden fruit, and it is she who then teaches him what he must do to acquire the Great Gift. The heavy price Eve subsequently paid to possess this knowledge was the grave sentence God leveled against her and her daughters: “I will greatly multiple thy sorrow and thy conception; in sorrow thou shalt bring forth children” (Genesis 3:16).
The Genesis story contains all the elements that I suggest actually converged at the dawn of our species, though in a somewhat different sequence. Maternal mortality was the primary cause, not the punishment, for the emergence of the first woman’s ego-consciousness. Eve did not commit the Original Sin; rather, the initiating event of our species was her exercise of Original Choice. The first man was not prodded by a threat to his existence comparable to what a female had to experience nine months after she stopped bleeding. He evolved cognitively in the area of sexual relations because she presented him with a threat that he could not ignore.
Adam confronted a knotty problem no other male of any other species ever had to contend with—a female with a mind of her own. She could refuse to mate with anyone, anywhere, anytime. Just as legend has it, that before Eve there was Lilith.*
A quirk of genetic linkages called pleiotropism spurred the first man’s rapid evolution. A human has twenty-three pairs of chromosomes. Only one of the twenty-three is considered the sex pair. As long as the gene controlling a trait is not on the female’s X or the male’s Y chromosome, the mixing of maternal and paternal chromosomes at conception guarantees that an attribute evolving in one sex, such as a nipple or a larger frontal lobe, evolves simultaneously in the opposite sex. As the female was gaining the mental grit necessary to assert her independence, she forced the male to respond to her act of will, because his individual fitness and the survival of the entire hominid line was at stake.
Eve’s independence compelled Adam to hastily assemble enough mental wattage to formulate the Brobdingnagian† question “What does a woman want?” Stripped down to its essence, what a man really wants to know is: “What must I do to convince her to let me have sex with her?”
Like Oedipus’ encounter with the Sphinx, death awaited a man’s genes if he failed to solve the riddle an aloof woman posed. Furthermore, the riddle was a multiple-choice question with protean answers, some of which might be correct in one situation but inappropriate for another. The enigma was complicated enough to force a man to evolve a big brain with large frontal lobes capable of dealing with so complex a mystery.
Of course, if he could not persuade her to join him willingly, he could, as a last resort, overpower her with his superior size and strength. However, aggressive males forcing themselves on unwilling females was not a satisfactory solution to the psychosexual emergency Gyna sapiens precipitated with her first adamant No! Sheer aggression between males and females has never, ever been used as the standard sexual strategy for any other species. From an evolutionary point of view, intersex mayhem would be too costly and dangerous to maintain. Rape in the wild remains an oddity, rarely observed. To install it as a mainstream adaptation in the hominid line would run counter to the tendency toward increasing cooperation that had been building steadily among the highly gregarious and social primates.*
With rape relegated to a rare and hazardous option, the human male found himself at a significant disadvantage as long as the female retained veto power over sexual congress. Nevertheless, the use and threat of rape in historical cultures has introduced a bitterness between the sexes that has poisoned male-female relations.
Since it was literally a matter of life or death to her, the woman retained the upper hand. Fortuitously for the frustrated male, Natural Selection stepped in and gave him an unexpected assist. Sophocles warned, “Nothing vast enters the life of mortals without a curse.” Her power to refuse sex was undeniably vast. The curse: Human females began to leak the crucial element iron at persistently alarming rates from a variety of avenues throughout their entire reproductive life.
The depletion of woman’s iron stores balanced her veto. Together, these two new adaptations—the ability to say No! and chronic iron loss—shaped the course of the many diverse human cultures that flowed from these two remarkable evolutionary developments. In combination, they also provide the answer to the timeless question “What do women want?” At its most fundamental level, the level present at the dawn of our species, what every woman wanted then was the substance that bestowed health and vigor on her and ensured that she birth smart babies. Ancestral women wanted iron. To understand better why iron is so critical and how it undergirds the structural I-beams of a human’s pre-eminent attribute—intelligence—we must make a brief digression.
We owe our superior mental agility to our big brain. Brains run on a mixture of two fuels: oxygen and glucose. The latter can be extracted efficiently from either fats, proteins, or carbohydrates courtesy of an enzyme system employed by the liver called the Krebs cycle. Every morsel you eat can be converted to a molecule of glucose.
During a crisis, such as illness or starvation, after your liver has exhausted its readily available reserves, it grimly sets to work cannibalizing the structural components of your body. Fat, skin, sinews, organs, and muscles all become grist for the mill as the liver grinds them down into simple grains of glucose. Implacable in its single-mindedness, the liver has a mandate to sacrifice everything to keep the brain operational, regardless of the debilitating consequences for any particular organ or structure. The liver “knows” what the community of other organs “know”—“If our brain dies, we are as dead as a doornail.”
In contrast to glucose, which is a foodstuff, oxygen is an element wafting in the air. Inspired through the lungs, it is transported through arteries, capillaries, and veins to a range of distant tissues by red blood cells. These dinner-plate-shaped discs are unique packets crammed with the spherical protein hemoglobin. A single hemoglobin molecule is huge compared with the average molecule. Yet the mighty engine of hemoglobin cannot function without its tiny spark plugs of iron atoms.
Blood loss from any source leads to diminution of the body’s iron stores. Unless replenished, this drop in the level of available iron leads inexorably to an iron-deficiency anemia. An anemic person suffers from lethargy and has a lowered resistance to many diseases. Iron-deficient pregnant women commonly deliver low-birth-weight infants, who more often fail to thrive, are at greater risk for mental retardation, and die earlier and more frequently than those birthed by mothers with adequate iron stores.
Human menses is an evolutionary mystery. Similar to the riddle that confronted the tongue-tied Parsifal standing in the Grail Castle hall, the question suspended in midair awaiting an answer is: This blood the woman sheds, what purpose does it serve? Why would a species evolve that profligately discarded so much of the indispensable liquid, especially when it does not seem to be a particularly important design feature of the vast majority of other females occupying the same mammalian phylum? Millions of females in the other phyla do not lose so much as a drop of menstrual blood during the process of reproduction. A contemporary human female will lose, on average, forty quarts of blood during her
lifetime of menses.3
As puzzling an adaptation as human menses is, it is only the first of six major sources of iron loss that shadow a healthy woman.
The second is the transfer of a mother’s iron stores to her fetus during gestation. The brain grows the fastest in utero. Demand for oxygen is exceedingly high in this crucial formative stage. Iron, therefore, plays a critical role during the normal development of the mammalian fetal brain. Among mammals, the human fetus attains the largest brain-to-body size. The only source for fetal iron is the mother’s iron stores. The implications for a pregnant woman are portentous. Not only must she keep up with the oxygen requirements of her own brain, but she must also supply the iron necessary to satisfy the demands of her unborn child’s mushrooming brain. In the last month of pregnancy, the fetal brain appropriates three-quarters of all the energy streaming in from the umbilical cord in the form of oxygen and glucose.4
The average daily dietary intake of iron is approximately one milligram per day in an adult man, slightly higher for a woman of reproductive age. A pregnancy causes the transfer of approximately 350 milligrams of iron from mother to fetus, or the amount equivalent to a year’s worth of the iron she would need to absorb if she was not pregnant.*
The third cause of iron loss occurs during delivery. Among mammals, there is no more difficult or dangerous labor than that experienced by a human female. The passage of a human life through a life, to enter life, is attendant with more blood, sweat, and tears than is the birth of any other mammal. Not for nothing is this travail called “labor” for the mother and “birth trauma” for her infant.
At birth, the exceedingly large mass of the human fetus’s head takes on the function of a battering ram. It stretches the mother’s woefully outmatched vaginal outlet beyond its limits. Not uncommonly, significant tears in the channel’s lining occur, especially during a woman’s first delivery. To prevent delivery lacerations of any degree, obstetricians can perform an episiotomy—a surgically controlled tear in an area away from the all-important anal-sphincter muscles that control fecal continence. This incision’s purpose is twofold. First, it enlarges the vaginal outlet, allowing the baby’s head to exit more quickly and with less resistance, thereby reducing the stress time on its vulnerable brain. Second, an episiotomy reduces the chances that the baby’s head will breach the integrity of the vaginal sheath.† This latter event, though rare, can lead to health-debilitating long-term complications.
The increased blood supply present in the pelvic tissues of a full-term female will result in brisk bleeding from a break in the lining due to any cause. No other mammal except a hyena has such a difficult time extruding its fetus through its vaginal channel.‡ And no other mammal experiences the severity and high probability of tears and lacerations of any kind in the process of birthing its young as a human.
The fourth major cause of iron loss also occurs during childbirth. Mammals bring forth living young that have been nurtured within the mother’s womb, unlike the eggs that birds and reptiles lay. Unique among the phyla, a mammalian mother succors her fetus by transferring nutrients in her bloodstream to the bloodstream of her developing fetus. The organ at the interface of this vital transmission is the placenta.
Several different types of mammalian placentas exist. Most have fairly definitive barriers of layered cells protecting the maternal bloodstream from the fetal one. The most efficient placenta, from a fetus’s point of view, exists in higher primates. Here, only the most gossamer of tissue divides the placental interface from the uterine one. Tiny blood vessels from each side create mini-lakes of blood separated only by a single porous membrane. As at an open border between two countries, goods and wastes move back and forth with ease.*
Among placentas, a human mother’s is the gold-medal winner. It can transfer to her fetus more nutrients more quickly than that of any other primate. If laid end to end, the absorptive surface of the blood vessels of the human placenta would cover thirty miles!6
The piper, however, must be paid. The critical fourth major source of iron loss occurs when the placenta separates from the uterine wall. Closely entwined blood vessels on both sides of the maternal-placental divide disengage, and a significant number of them are torn in the process. After separation and before the placental delivery, there are critical moments when the divot in the uterus resembles a large raw wound. Between half a pint and over a full pint of blood typically escapes from the mother during this interval. The uterus’s charge is to clamp down immediately and compress the open blood vessels to stanch the bleeding.†
Although this is nature’s effective method to minimize blood loss, it is not instantaneous. And with each successive pregnancy, the force of these post-delivery contractions weakens. In spite of the womb’s best efforts, the gush of blood from the placental separation can be alarming. Anyone witnessing a live human birth comes away deeply impressed with how bloody mother, baby, sheets, floor, and the hands and gown of the deliverer become.
“Lochia” is the name of the slight bloody discharge that continues for several days after a human delivery. Although minimal, it is not inconsequential. Its amount and duration in a human mother exceed that of any other mammalian mother. The combination of tears, lacerations, episiotomies, placental separation, and lochia constitutes a loss of blood, and therefore iron, far in excess of any other mammalian species—five hundred to a thousand milligrams of iron, or the equivalent of one or two pints of blood. One-eighth to one-tenth of a mother’s entire iron supply exits at delivery, having been absorbed into the fetus and the placenta or squandered profligately during delivery.
The fifth major cause of iron depletion in Gyna sapiens is not so obvious as the previous four but nonetheless significantly increases her risk of developing an iron-deficiency anemia. The transfer and loss of iron associated with gestation and birth exist to a lesser degree in other mammalian mothers but still pose a problem. To counter it, Mother Nature equipped females of the other mammalian species with a vital instinct—an urgent hunger driving them to consume their offspring’s placenta. A plump soufflé of meaty iron, amino acids, and essential fats, the placenta is the consummate first meal a mother should partake of immediately after the ordeal of delivery. It is the perfect replacement for the very nutrients she lost just minutes earlier, because a freshly expelled placenta contains the iron equivalent of one or two blood transfusions.
Gyna sapiens has lost her craving for this delicacy. Our closest relatives, chimpanzees, dine with gusto on their afterbirth immediately after delivering their infants. In contrast, nurses whisk away the placenta before a mother can even catch a glimpse of it, so that it can be discarded in the trash. Present-day hospitals label the placenta “toxic waste” and issue strict regulations governing its disposal. Among many other human cultures, placentas are thrown to dogs, who, recognizing a valuable resource, gratefully devour it.* Failure to ingest the placenta constitutes the fifth significant source of iron loss in the human female (albeit a passive one).
The sixth and last major source is perhaps the most pernicious. Newborns spend the majority of their time suckling and sleeping. They should. Infants are a complex, incomplete building project feverishly under construction; no wonder they are exhausted most of the time. During the period of breast-feeding, the baby’s brain grows rapidly. In the first year of life alone, it more than doubles in size as it steadily lays down layer upon layer of new brain cells.
To get the job done, newborns require a constant energy source. Now that they are breathing on their own, they need to put in place quickly their own elaborate transport system to carry oxygen from lung to organ. Their most demanding organ is their rapidly enlarging brain. And where, we might ask, does an infant derive all the iron needed for its shiny new red cells? Again, the mother is the only source of this crucial element.
Human breast milk constitutes another significant source of iron loss for a woman. Even though it is not especially rich in iron, the duration of its loss makes up f
or its concentration. Unlike the sudden exodus of red cells at delivery, lactational iron loss occurs steadily over a span of several years. Observations among hunter-gatherer lactating women, such as the !Kung San of the Kalahari, reveal that on average they breast-feed their young for an average of two years and eight months.8
Anthropologists use the customs of these and other hunter-gatherer peoples to extrapolate back in time and make approximate predictions concerning ancestral women. Breast-feeding for almost three years represents a steady but incremental drain on a lactating mother’s iron stores. Again, changes in her digestive system rapidly increase her gut’s ability to absorb iron from foodstuffs, but iron-rich food must be available to her before she weans her baby. During the time a mother is breast-feeding, complex hormonal adjustments in her system forestall menses in all but a few cases.
Within a month or two after separating her toddler from her breast, just as night follows day, the mother begins to menstruate again. But a new factor will cause her to lose more blood with each menses than she did prior to her pregnancy. Once a woman has had her first child, the increased size and more robust vascularity of her uterus will cause a small but significant increase in menstrual loss of iron. Each subsequent pregnancy will be followed by a slightly heavier menstrual flow, and this trend will continue for the rest of the woman’s reproductive life.9
Sex, Time, and Power Page 5
