Human Evolution and Women’s Sexuality -- Part IV: Why Do Women Bleed?

By Kristy McCaffrey

Don’t miss ~

Part I: Women Acquire Free Will

Part II: Women Bleed And There’sNo Practical Purpose

Part III: What Do Women Want?

Human males are saddled with a sexual desire that rarely wanes. While other male species will see a spike in testosterone levels in conjunction with the mating cycles of females, human males maintain a steady concentration year-round.

Because ancient human females had such high iron needs due to the many sources of blood loss in her lifetime (menses, childbirth, and lactation), a peculiar adaptation occurred in the male—constant, high levels of testosterone. One theory proposes that this pushed the male to take ever greater risks—to hunt that giant animal that could trample and kill him—all to return with iron-rich meat for the female and her offspring, his insurance plan for sex. But the side effect of this has been a disparity in the sexual needs of men and women.

Women require significantly more iron than men. Men have incredibly high testosterone levels which create an intolerable sexual tension that demands release. These two situations are intimately linked.

In many early cultures, hunting was equated with sex. The better hunter a man was, the more opportunities he had with willing females. To state it crudely, a good hunt exchanged meat for sex. Females encouraged this further by favoring males who were the best hunters, bringing back meat to replenish her lost iron stores.

But, ultimately, it was the adaptation of time that gave males the advantage they needed to become successful hunters. And it was the females who imparted this wisdom. Humans learned to anticipate the arrival of certain animals—migrations—and to plan accordingly. They gained foresight.

Because the female had sent the male out to hunt due to her need for iron and his never-ending desire for sex, she needed to arm him with an advantage. Naturally, over time, men would take the credit for this, but women know better. Due to her menstrual cycles, her sense of time changed. She could forecast into the future, and she shared this knowledge with the men. Learning to tell time is an exceptional evolutionary development, one that humans share with no other species. (Some creatures do exhibit similar behaviors, but these can be credited to instinct.)

Humans can plan, we can choose a course of action. We understand that one day, far in the future, the sun will cease to be. We know that we exist in a three-dimensional paradigm. Even the most intelligent of other species—dolphins, elephants, and higher primates—are unable to grasp these issues.

And this is perhaps why a woman’s menstrual cycle is linked to the motions of the Moon. Or, said in another way, because her cycles mirrored a lunar one, an inherent sense of time was born within the female mind.

In many cultures, menstruation is referred to as ‘the moon’. In rural India, the moon is believed to be the ‘cause of all time’, just as it is the cause of menstruation. Long ago, menses, the moon, and the duration of a month came together and forever changed a female human’s ability to navigate a different time-space.

In his book Sex, Time and Power: How Women’s Sexuality Shaped Human Evolution, author Leonard Shlain writes, “Foresight has proved to be the sexiest idea that Mother Nature came up with since Her clever invention of the penis two hundred million years earlier. Whereas the penis significantly advanced the fortunes of every reptile and mammal species that acquired one, foresight dramatically increased the fortunes of only humans, at the expense of all other species.”

Why do women bleed so much? Shlain posits that it is so humans could anticipate the future, something no other animal had ever before accomplished.

So, back to the initial question—why do women lose so much blood each month? The answer is because it was necessary for human evolution. And what was this evolution? Linking a woman’s bleeding, an event too big to ignore, with the cycles of the moon taught humans how to tell time. The ability to practice foresight was and is the most important asset we possess as a species.

The price for all of this was the depletion of iron in human females. To combat this, they reshaped their sexuality, incorporating a system of free will when it came to choosing sexual partners, and males were forced to comply with this turn of events. Negative outcomes have been patriarchy, misogyny, and the use of rape, but positives have been males who exhibit more kindness, compassion, and love to their mates—and offspring—than any other species on earth.

To learn more about this fascinating subject, I encourage you to read Sex, Time and Power: How Women’s Sexuality Shaped Human Evolution by Leonard Shlain (Penguin Books, 2003).

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Human Evolution and Women’s Sexuality -- Part III: What Do Women Want?

By Kristy McCaffrey

Don’t miss ~

Part I: Women Acquire Free Will

Part II: Women Bleed And There’s No Practical Purpose

“What must I do to convince her to have sex with me?”

If you strip away every cultural accoutrement, every interplay between the sexes, it whittles down to this basic question of males. Women acquired the ability to refuse sex as an adaptation to the dangers of childbirth—if she would die, she would choose when, where and with whom she became intimate. So, the age-old dilemma of men was born, “What do women want?”

On a side note, the issue of rape must be addressed. Men frustrated and unwilling to cooperate with these new set of rules put forth by human women have, and still do, practice the overpowering of females. They practice rape. This is not a healthy mating strategy and society consistently shuts down this taboo, yet, as we know, the practice continues. This has created a bitterness that still poisons male-female relations today.

But having the choice of saying no has come at a cost to women. Every month they bleed and deplete their stores of iron.

 So, what do women want? They want iron.

A red blood cell’s main function is to pick up oxygen in the lungs, transport it through the blood vessels, and deliver it to every organ in the body. A healthy man has 15 percent more red blood cells than a woman. In order to function, a red blood cell requires a protein called hemoglobin. At the center of hemoglobin is the element iron.

Iron leads to well-being and vitality and ensures that a woman can birth healthy babies. Women lose iron not just through menses, a process that will deplete approximately forty quarts of blood during her lifetime. Blood loss also occurs during pregnancy, when a mother transfers her iron stores to her fetus. The average dietary intake for a woman is about one milligram of iron per day. During pregnancy, she must transfer 350 milligrams of iron to her unborn child, the equivalent of a year’s worth of the mineral.

A third cause of iron loss occurs during delivery. Vaginal births can release bleeding in the pelvic tissues. No other mammal experiences such difficult births as a human woman.

A fourth cause of blood loss also occurs during childbirth, concerning the placenta. Human women are the winners in the placenta arena. It can transfer more nutrients more quickly than any other primate. But when the placenta separates from the uterine wall, nearly a full pint of blood will be discharged from the female.

A fifth source of blood loss is a bit more circumspect, but nonetheless important. All other mammalian females have an urgent hunger to consume the placenta when expelled. Human women have lost their craving for this delicacy. The placenta is filled with iron, amino acids and essential fats; it has everything a mother needs to replenish herself following birth. It’s the equivalent of one or two blood transfusions, but most hospitals label the placenta as toxic waste.

The final, and sixth, source of iron loss for women occurs during breast feeding. Infants must get all their iron from their mothers to fuel their immense brain growth. Lactational iron loss occurs more slowly over a span of several years.

Iron must be eaten, and unfortunately for humans most plant-based iron is unavailable to us. The human digestive tract lacks common but critical enzymes that aid in the absorption of iron from plants. But we can digest iron from animal sources. A side effect of our ancestors gravitating to a more meat-based diet was the shortening of our guts. This freed up more oxygen for our brains, and hence our brains became larger, and intelligence flourished. In general, carnivores are smarter than herbivores. A coyote is slyer than a cow.

Man as hunter is born.

Painting by Emmanuel Benner (1836-1896)

Don’t miss Part IV: Why Do Women Bleed?

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Human Evolution and Women’s Sexuality -- Part II: Women Bleed And There’s No Practical Purpose

By Kristy McCaffrey

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Part I: Women Acquire Free Will

Let’s talk about periods.

At the beginning of a new cycle, the interior of a human uterus appears dead. Slowly, as ovulation approaches, an orchestration of hormones creates a lush farmland. Both estrogen and progesterone levels rise steeply. Blood vessels flourish, growing fat and full. If fertilization doesn’t occur, Mother Nature swiftly discards the entire setup. Estrogen and progesterone begin to slowly retreat, but then plummet drastically. The entire system goes into a death spasm. Within this tomb, a lake of blood forms, and like a dam breaking, gushes forth to the cervix.

Whenever any organ tissue dies and remains in the body, toxic substances are released and threaten the life of the host. For human females, slowly releasing these substances isn’t possible, so a process was needed to rid her body quickly of pathogenic bacteria and poisonous byproducts of cellular death. The solution was the opening of the cervix, uterine cramps to discard the lining, and the elimination of 4-8 tablespoons of blood. A woman’s period has begun.

Back in caveman days, menstrual odor would have been a serious attractor of predators. Add to that the general fear present in the males. A bleeding animal becomes weaker and a hunting male would take this as a sign of impending death. But what about when he caught a glimpse of a bleeding human female? She wasn’t injured and didn’t become weaker. Intercourse would likely leave blood on the penis, adding to a man’s fear of castration. Distance would soon be sought from menstruating females, since their condition was unexplainable and relegated to the realms of magic. This would soon breed fear and resentment toward women.

Establishing rules of conduct, geared mainly around hygiene issues, would have been of high concern to early ancient peoples. Unfortunately, many of these instructions have been used to strip power and autonomy from women over time. Pliny, from the first century, warns men that a menstruating woman can, by her touch, “blast the fruits of the field, sour wine, cloud mirrors, rust iron, and blunt the edges of knives.”

Women have always seemed to intuitively know that during menses a time of rest is required. With the body being so vulnerable, it is nature’s way of protecting a defenseless organism. During a woman’s period, she is more susceptible to uterine infections. Toxic-shock syndrome occurs because a tampon has prevented the discharge of menstrual blood, allowing harmful bacteria to take hold.

Historically, cultures celebrated the onset of menses in a young girl by enacting any number of initiations and rituals. Consistent throughout all of these was to impress on the girl that she was in possession of a great power and responsibility, and she was not to dispense future sexual favors easily for they were quite valuable.

Other mammal species have loads of babies—cubs, kits, puppies and the like—without the loss of significant amounts of blood and protein-rich tissue monthly. In fact, while dogs bleed during their period of heat, they’re also blessed with the ability to lick themselves, thereby recycling that iron trying to escape their bodies.

Overwhelmingly, there is no scientific evidence to support a benefit to human menstruation. What purpose does all this bleeding serve? With so many drawbacks to the human female, why hasn’t natural selection eliminated it long ago?

Don’t miss Part III: What Do Women Want?

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Human Evolution and Women's Sexuality -- Part I: Women Acquire Free Will

 By Kristy McCaffrey

Women bleed. Men don’t.

According to biologists, there are between ten million and thirty million different species of life on earth. Only four thousand are mammals. And only one—humans—experience blood loss on a regular basis. If fertilization doesn’t occur each month, a human woman will menstruate, shedding the lining of her uterus along with several tablespoons of blood every four weeks. There are mammals who exhibit a type of menses—elephants, bats, shrews and hedgehogs—but it’s insignificant to their health. And out of approximately 270 different primate species, 31 menstruate, but again, the blood loss is negligible.

Over 150,000 years ago, the hominid brain completed a rapid inflation that added one-third to its size. This wasn’t good. No other species has as difficult or as dangerous a labor as a human woman. And no other female needs as much help from others to give birth.

The human brain consumes nearly 25 percent of every heartbeat’s oxygen-rich output. The brain’s pH and temperature must be narrowly regulated. The body must constantly clear the accumulating toxins from the fluid that bathes the brain. Why do we have such a large brain that requires so much of our body’s resources? In his book Sex, Time and Power: How Women’s Sexuality Shaped Human Evolution, author Leonard Shlain posits that it has to do with three things: sex, iron, and time.

The most amazing feature of today’s human woman is that she has the willpower to refuse sex around the time of ovulation. She can even remain celibate, if she so chooses. This is a direct consequence of birthing babies with large heads, which resulted in a high maternal mortality and painful childbirth.

A major overhaul of the brain was required for females to acquire the ability to exercise free will. With the expansion of the neocortex and the frontal lobes, along with the refinement of highly-specialized areas of both hemispheres, a female gained control of her sexual urges, much more so than the male. She acquired the ability to contemplate the relationship between mating and childbirth, a dangerous endeavor for her. She gained time to reflect, to understand that nine months after copulation resulted in offspring. She was able to connect the past with the future.

Female women underwent a major transformation because they were dying in childbirth. By gaining control of her sexual urges, she was able to control conception. And this would have profound effects on both women and men through time.

Don’t miss Part II: Women Bleed And There’s No Practical Purpose

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