With the cessation of lactation, a woman’s menstrual cycle begins anew. One constant remains: By one avenue or another, a woman is always losing iron. Over a lifetime, the average woman loses the equivalent of approximately fifteen gallons of iron-rich blood due to menses, pregnancy, delivery, birth trauma, placental loss, failure to consume the expelled placenta, and lactation. If she has access to sufficient dietary replacements, she can easily make up for this loss. However, a crisis occurs if she encounters a problem in either her health or her diet which interferes with her acquisition of iron.
Recent research carried out by the increasing number of female anthropologists entering the field suggests that modern women lose more blood from more frequent menses than did the women of ancestral times. Studying the indigenous Dogon tribes in Mali, anthropologist Beverly Strassman found that the fertile Dogon women are in a near-continuous state of pregnancy or breast-feeding. Also, the onset of menarche occurs later than it does in modern cultures.10 Strassman calculates that the average Dogon woman experiences 110 periods during her reproductive life, compared with over four hundred for women living in the industrialized West.11
Reading the literature on hunter-gatherer reproductive statistics might leave one with the impression that as soon as a mother weans her toddler, she immediately begins another pregnancy, leaving no space for menses to squeeze in between lactation and the next conception. But this is not the case. The Dogon practice agriculture and they are not representative of pure hunter-gatherers. Anthropologist Sarah Blaffer Hrdy documented in her book Mother Nature the nearly universal practice among hunter-gatherers to practice abortion and, if necessary, infanticide as methods of family planning. Women in hunter-gatherer societies generally try to space their children at least four years apart. Attempting to care for, feed, and nurture too many children too close together places great stress on both the mother and her tribe. A number of menstrual months occurs between the end of one lactation and the beginning of the next pregnancy. Nevertheless, some women in extant hunter-gatherer tribes recall having few menses during their reproductive life.
There are additional factors. Several obstacles unique to humans exist that make serial pregnancies chancier for them than for other mammals. Reproductive physiologists estimate that it takes, on average, three menstrual cycles of concentrated lovemaking among young, healthy human couples to conceive. The reasons for the delay are several.
The incidence of miscarriages is 40 percent in the first trimester of pregnancy. Many of these occur before a woman even has an inkling that she is pregnant. A woman experiencing such a loss would have to rejoin her partner in another ninety-day cycle of lovemaking to conceive again.12 There is little reason to doubt that ancestral women experienced the same percentages of lost fertilized ova. (The possibility cannot be dismissed, however, that modern culture has introduced a number of artificial environmental toxins that may be affecting the odds of conception and the percentage of miscarriages—factors with which ancestral women did not have to contend. But this would have been offset by earlier women’s much higher parasitic loads.)
Any deficiencies in the health of either member of the pair, when added to the factors elaborated above, make conception in humans a hit-or-miss affair. During the not inconsiderable number of months when a sperm and an ovum were trying to link up, a woman would experience several menses, each requiring iron replacement. Sarah Hrdy in her study of !Kung women estimated that one-half of them died childless.*13
Strassman’s research on the Dogon women, however, does not mean that the fewer menses among her subjects translate into less iron loss than among contemporary women. The iron drain from the other five major sources for blood loss exceeds the not insignificant amount of blood ejected with each of nine periods she missed by being pregnant. The iron loss from lactation also exceeds the amount that would have been lost in menses over the two years and eight months of breast-feeding.
Whether a !Kung woman is menstruating, gestating, or lactating, she is constantly losing iron. Although they had less frequent menses than modern women, fertile ancestral women still needed to establish a safe and effective way to replenish their iron stores. (And this does not take into account the woman’s body’s urgent requirement to restock its warehouses of proteins, fats, vitamins, and minerals.)
Along with the six major iron-leaching causes, there exist four minor, variable bloodletting pathways that can harass women of reproductive age. The first two—polyps and fibroids—are created by the unique cellular composition of a woman’s uterus. Imagine a TV weather personality delivering nightly forecasts for each of the body’s regions. Weather reports for kidneys, eyes, hair, bladder, and toenails would be monotonously boring, because each area experiences fairly constant climes. The “weather” in the uterus, in contrast, is constantly in a state of flux. Furthermore, a destructive storm regularly lays waste to the landscape. No other organ manifests such a striking change in its appearance during each month, and none has so dramatic and repetitive a cycle of growth, maturity, and death.
Bones and teeth, for instance, once they have stopped growing, remain essentially unchanged structurally for the rest of life.* The heart is certainly dynamic in function, but though it constricts and relaxes seventy times a minute, little change occurs in the life cycles of its component cells. White blood cells and the mucosal† cells that protect the lining of the intestinal tract turn over every few days. Their individual cell cycles, however, are conveniently out of phase with each other. When some cells are young, others are mature, while others are dying. Because of their asynchronicity, the appearance of these organs does not vary from day to day.
A very different situation takes place in the uterus, whose tissues take their orders from hormones secreted by distant glands that convey widely conflicting directives. Most cells lining the uterus respond in lockstep to these monthly comings and goings, compelling the uterus to fluctuate in both its internal structure and its appearance.
Cells find it easier to escape from the normally strict biological controls regulating the manner in which they grow if they live in a whipsawed environment. The uterus is the Wild Western frontier of the body. Cellular lawlessness is common. In the course of a woman’s reproductive life, she is likely to develop several abnormalities that exacerbate cervical and uterine bleeding.
Polyps and fibroids are overgrowths of cells that have rebelled against the body’s strict cellular-growth regulators. These sporadic rogues’ independence movements can occasionally transmogrify into cancer. Fortunately, the vast majority of both polyps and fibroids remain benign. Nevertheless, they can cause local problems.
Polyps are heaped-up mounds of exuberant cells arising from the cervical and uterine lining. Older medical textbooks called polyps “proud flesh” because they stand up and out from the surrounding normal tissue. These slightly abnormal cells are very fragile, tend to bleed easily, and are one of the most common causes for “spotting” between periods.
Fibroids are benign tumors consisting of uterine muscle cells that have experienced runaway growth. Stimulated by estrogen and progesterone, they are usually multiple in numbers. Though slow-growing and usually painless, some can reach prodigious proportions. Fibroids arising close to the interior of the uterus can cause a thinning of the delicate inner lining. Eventually, the tumor stretches the lining to the breaking point, causing persistent “spotting” from the exposed raw surface of the tumor. In some cases, bleeding fibroids can produce a life-threatening blood loss. The surgical removal of the uterus will definitively stop the bleeding from any abnormal condition, but this recent medical advance was not available to ancestral women.
We have a record of just such blood loss in the New Testament. Luke, a physician, relates the story of a woman who sought Jesus’ help because she was plagued by “an issue of blood for twelve years” (Luke 8:43–48). “Menorrhagia” is the medical term for her abnormal uterine bleeding. Her anguish is evident in the passage. It is reason
able to assume that uterine bleeding from pathological conditions also vexed ancestral women. Physicians treating a patient with menorrhagia routinely prescribe iron supplements. Only after menopause does a human female’s daily iron needs stabilize to mimic those of a male. Even then, her total body reserves remain below male levels.
In addition to polyps and fibroids, the third minor source of iron loss plaguing women (which can also beset men) is the dreaded hemorrhoid. A uniquely human condition, it was the direct result of our hominid ancestor’s fateful decision to stand up and walk on two legs instead of four. In virtually every other mammal, the anus and heart occupy the same horizontal plane. Venous blood returning from a hind end can flow lazily back to the heart, usually downhill.
Upon assuming an upright stance, a hominid positioned its heart approximately two feet above its anus in a vertical plane. This created a bedeviling hydraulics problem. Arterial blood flow hurries along on its appointed tasks, urged onward by the propulsive force of each systolic heartbeat. Once on the venous side of each capillary, however, the movement of blood slows to a sluggish crawl, since there is no pump propelling it back to the heart. In humans, venous flow returning to the heart from the pelvis must defy the force of gravity, heading straight uphill. As a result, the veins underlying the delicate lining of the distal rectal tract remain permanently engorged, because there is a several-foot-high column of blood pressing down from above.
Exacerbating the problem of hemorrhoids is a most curious behavior. Humans are the only animal in all the phyla that must learn at a very early age to maintain tight control over their anal sphincter.* To the ever-constant delight of small children visiting the zoo, animals generally poop whenever the urge moves them.† Having recently suffered through the intense period dreaded by both parent and child known as “toilet training,” it is no wonder that children marvel at all other animals’ lack of inhibition.
Controlled defecation must have developed relatively early in our evolution. Hominids were the first mammals to congregate at a semipermanent home base, to which they brought food to prepare. Our ancestors discovered through trial and error that it was imperative to train their young to control their sphincters to prevent the spread of disease.
One can accurately gauge the level of anxiety concerning this subject in human culture by the hearty laughter and continual fascination it evokes in children and many adults. It could be said with assurance that, despite the plethora of varying cultural traditions throughout the world, losing control of one’s bowels in public ranks in all of them as the most humiliating of social gaffes. A physiological side effect of this idiosyncratic human cultural convention is that the human anal sphincter is in a state of near-perpetual constriction. The small circular muscle squeezes the veins around it, engorging them further, making them more susceptible to bleeding.
Pregnancy significantly exacerbates the problem. Hemorrhoids tend to recur even after the woman has delivered. Women, more than men, suffer from bleeding hemorrhoids. Blood loss from hemorrhoids alone can cause a significant chronic anemia. Physicians treating a patient with bleeding hemorrhoids, short of surgical intervention, routinely prescribe iron supplements.
A fourth precipitating cause of female anemia from iron loss is the tiny hookworm parasite, which is in fact the leading cause of iron-deficiency anemia throughout the world for both sexes. Until the era of modern medicine, parasitic infestations were unwelcome hitchhikers common to all human societies. Even today, the World Health Organization estimates that a quarter of the world’s population is infested. Hookworm can tip a marginally anemic woman over to one who suffers the full manifestations of the disease.
One other important factor adds to a woman’s iron woes. A slight anemia translates into heavier menses and more blood deficits from delivery loss. This sets up a vicious cycle difficult to break. The more anemic a woman is, the more blood she loses, making her more anemic and causing increasing iron loss.
When taken as a whole, the six major sources of blood loss in a woman and the four minor ones are quite puzzling. No other female animal possesses what can only be characterized as a suite of traits that predispose its possessor to the threat of ill health. The question arises—why? Of what conceivable benefit could it be to the fertile female to lose iron constantly and skirt the edge of anemia? How did this piling of one seemingly negative adaptation after another serve to advance the overall fitness of the species? And why would this deleterious iron drain occur in only one sex of that one species?
Health authorities in the First World have masked a woman’s need for iron. Recognizing the role the red metal plays in her health and the health of children, manufacturers have fortified most packaged foods with iron supplements in a form that is easy to absorb. Scrutiny of the fine print on any cereal box will confirm the presence of the additive. This simple act has greatly reduced the incidence of iron-deficiency anemia among women fortunate to live in such societies. To avoid making comparisons to women living in a technologically advanced society, the point is worth emphasizing. At the dawn of our species, women did not possess this luxury. Once humans left equatorial Africa for climates more extreme, their access to dietary sources of plant iron, especially in winter, became restricted. In order for both them and their babies to be vigorous and mentally sharp, women became highly motivated to find a way to ensure a reliable source of bioavailable iron for their diets.
The foodstuff highest in absorbable iron is blood. Ironically, there exists a powerful taboo in almost every culture in the world against drinking blood. The vampire myth, for example, is among the most frightening in many cultures, and probably arose to forestall the practice of cannibalism.* The food resources second highest in iron are liver and bone marrow, and the third and most plentiful is meat. Consuming any of these animal products is the easiest and fastest natural way to replenish depleted iron stores. So how would an ancestral woman have guaranteed that she would have ready access to the iron she and her offspring so desperately needed?
Of the 270 species of primates, only one consistently hunts other animals.
Chapter 4
Plant Iron/Meat Iron
There is no question that a reconstruction of ancestral mating systems will be an essential part of any satisfactory account of human origins.
—Martin Daly and Margo Wilson1
Some [indigenous] women in North America avoided meat during pregnancy out of their very practical desire to keep their developing fetus small, to avoid complications or death in childbirth.
—Judy Grahn2
Mother Nature is spectacularly elegant. And She loves the color green—all shades of it. The world wears green because plants possess the tiny but mighty molecular engine, chlorophyll. A photon hurled outward from the superheated surface of the sun speeds toward the earth in the form of a minuscule fireball covering 186,000 miles in a second. Try to intercept one and—splash!—it explodes in an energy wave that dissipates as heat in an instant. Chlorophyll somehow manages to catch these speedy messengers from the sun in slow motion, thereby harnessing the sun’s light and converting its energy into the mass of the plant. All stems, trunks, flowers, and leaves are the living proof of this wondrous transmutation.
The core of chlorophyll, the marvel behind the process of photosynthesis, consists primarily of hydrogen, carbon, oxygen, and nitrogen atoms arranged in a ring pattern. At the exact center of this complex molecule rests a single atom of magnesium—a dull-gray metal that gives much of the world its leafy-green color. Substitute that single magnesium atom for one of iron—and presto!—a chlorophyll molecule magically transforms to resemble closely the core of hemoglobin. Iron ore, another dull-gray metal, plays an important role in coloring the innards of all complex animals red. Green for plants; red for animals. So beautiful, so simple.* In the preface, I spoke of experiencing moments of pure rapture when I learned certain details concerning the workings of life. Encountering the complementarity between chlorophyll and hemoglobin was one
such moment of awe. Evolutionary nutritionist Michael Crawford, struck by this similarity, comments, “The hemoglobin of the red cell is so close in structure to chlorophyll…it makes one wonder if the genetic information of the red cell came from a mutation of the chloroplast data.”3 Because the early part of this book’s thesis hangs on the hook of iron, how an iron atom makes its way into the center of hemoglobin is pertinent to the story I plan to unfold.
Iron is a fundamental element, one of the 118 found in the periodic table. It must be eaten, because it cannot be manufactured from constituents in the body. The iron atom has two stable forms: ferrous (Fe++ or Fe2) and ferric (Fe+++ or Fe3). Since iron is a major constituent of soil, and plants grow in soil, iron is a structural component of many fruits, grasses, grains, and vegetables. Unfortunately for humans, most plant iron is unavailable to us, because both forms of the iron atom are tightly bound to the plant’s organic molecules (such as phytates, tannins, and many others) in a process called “chelation.” Plant-eating animals possess digestive processes that can readily strip the metal away from the chelating molecule’s steely grip to incorporate the vegetable’s iron into their hemoglobin. Mysteriously, the human digestive tract lacks the common but critical enzymes that facilitate the rapid absorption of the iron from many vegetal foodstuffs.†
The Fe+++ in plants is more difficult for a human digestive tract to absorb than Fe++. Spinach, famously rich in iron, contains primarily its chelated ferric form. (Popeye, contrary to expectations, would not have received much of a jolt from his famous spinach gulp.)
These two nutritional impediments, one major (chelation) and one minor (iron in its chelated ferric form), are the principal reasons why the majority of iron contained in vegetables passes through the human intestinal tract unabsorbed.
Sex, Time, and Power Page 6
