As in the bestselling The Alphabet Versus the Goddess, Leonard Shlain's provocative new book promises to change the way readers view themselves and where they came from.

Sex, Time, and Power offers a tantalizing answer to an age-old question: Why did big-brained Homo sapiens suddenly emerge some 150,000 years ago? The key, according to Shlain, is female sexuality. Drawing on an awesome breadth of research, he shows how, long ago, the narrowness of the newly bipedal human female's pelvis and the increasing size of infants' heads precipitated a crisis for the species. Natural selection allowed for the adaptation of the human female to this environmental stress by reconfiguring her hormonal cycles, entraining them with the periodicity of the moon. The results, however, did much more than ensure our existence; they imbued women with the concept of time, and gave them control over sex a power that males sought to reclaim. And the possibility of achieving immortality through heirs drove men to construct patriarchal cultures that went on to dominate so much of human history.

From the nature of courtship to the evolution of language, Shlain's brilliant and wide-ranging exploration stimulates new thinking about very old matters.

There is a female human nature and a male human nature, and these natures are extraordinarily different.... Men and women differ in their sexual natures because throughout the immensely long hunting and gathering phase of human evolutionary history the sexual desires and dispositions that were adaptive for either sex were for the other tickets to reproductive oblivion.

— Donald Symons

Error is the inevitable by-product of daring.

— Stephen Jay Gould

Juxtaposing the words "iron" and "sex" creates an odd couple. The two rarely have occasion to appear together in the same sentence, much less find themselves standing side by side with so little editorial support. In the following pages, I will propose that the first word fundamentally influenced economic matters between men and women and, as a result, profoundly affected the politics of the second word. Along the way, I will present a scenario for how the kaleidoscopic, maddening, exciting, enchanting, and baffling man-woman dance, more commonly referred to as "a relationship," evolved.

This book arose out of a question I posed to a professor when I was a second-year medical student, making rounds on patients in a large ward. Although the incident occurred over forty years ago, I had never really forgotten or accepted his answer.

The sophomore year of medical school represents a major transition for students. They leave the cadavers of the freshman year behind and begin having contact with respiring, perspiring patients. On this particular day, we were being taught how to interpret laboratory results.

Shifting from bedside to bedside, our knot of students listened intently to the professor. Every patient admitted to the ward, he explained, had three basic laboratory tests: a chemistry-26 panel, a urinalysis, and a complete blood count (CBC). The first measured the concentration of twenty-six constituents floating about within the patient's bloodstream.

The amount of a patient's circulating sodium or potassium, for example, provided a snapshot of the health of various internal organs, such as the heart and kidneys. The measurement of every one of the twenty-six constituents was like having a miniature finger figuratively take the pulse of some very important cellular function, which in turn reflected on the state of one or more of the body's organs. The lab reported each value on a slip that was placed in the patient's chart. Neatly aligned, parallel to the patient's results, was a column stating the expected normal ranges for each particular variable. What caught my eye that morning was the list of normals. Of the twenty-six numbers on the chem panel, none distinguished between the values for a man and a woman. And why should there be any? After all, sex has nothing to do with the way a lung or a stomach goes about its business, so I would not have expected any variation between the sexes. The same held true for the normal values reported on the urinalysis.

The CBC, however, was distinctly different in this regard. A complete blood count measures several different parameters of the red and white cells circulating within the body's miles of vascular tunnels. Although the white-cell numbers were the same for the two sexes, I noticed that the red-cell normals for men and women were surprisingly askew. I thought that was very strange.

A red cell's chief function is to pick up oxygen in the lungs, transport it through the blood vessels, and deliver it to every organ in the body. For all complex creatures, oxygen is the staff of life. Deprive them of this most precious element and they will rapidly die of asphyxiation. Yet a man normally has a 15 percent higher concentration of circulating red cells than a healthy woman has. I puzzled over this discrepancy (even after taking into account that, generally, a woman is smaller in stature and has less muscle mass than a man), and it prompted the question that lies at the heart of this book. Why would a woman need less of blood's critical essence than a man?

I raised my hand and asked the professor to explain the reason for this vital disparity. He replied, in a way that suggested he thought the answer was obvious and my question, had I given it more thought, was unnecessary:

"Women bleed and men don't."

Somewhat annoyed that I had interrupted his train of thought, he then returned to the subject on which he had been discoursing. I reddened.

I remember thinking at the time that his curt answer could not be the whole story. Later, as I turned over his reply in my head, I could not think of a plausible explanation for this difference. Why would a species evolve whose females but not males operated routinely on less than a full complement of tankers to ferry a fuel as crucial as oxygen? (One could argue that the female has a normal amount and the male has a 15 percent excess capacity. Either way, the inequality begs for an explanation.)

The magic behind a red cell's seamless performance is the protein called "hemoglobin." And, like a set of nested Russian babushka dolls, at the core of hemoglobin lies the element iron. Iron and oxygen, because of the salutary arrangement of their outer electron shells, eagerly seek out each other's embrace. Once merged, the two form a molecule called iron oxide. Everyone is familiar with this substance. We call it "rust."

Rust has a signature red color. Iron oxide in rock lends to the Grand Canyon its spectacular chromatic array. It colors the fields in Kenya and the plantations of Hawaii, and rust's distinctive hue made the earth of Scarlett O'Hara's beloved Georgian Tara red. The hemoglobin molecule, with its precious complement of iron atoms, makes blood red and white skin pink, and it tints medium-rare steaks with a distinctive ruby sheen.

Hemoglobin transforms iron's strong affinity for oxygen into a delicate "grasp and release" maneuver, allowing oxygen to be easily acquired in the lungs and readily relinquished farther down the line to the cells. The felicitous combination of iron, oxygen, and hemoglobin is central to the process that facilitates the neurons in your brain to extract meaning from the sequentially aligned squiggles you are reading on this page.

A few weeks after I had posed my red-cell question on rounds, a second incident piqued my interest in the subject. During a rotation on the obstetrics-gynecology service, I was assigned to the prenatal clinic, where wise, experienced nurses instructed me how to care for pregnant women. Detroit's Harper Hospital in 1958 served a large population of poor people who had emigrated from other states, hoping to improve their lives in the city's then booming auto industry. Unfortunately, most women we served were unaware of the prenatal program and did not enter it, if at all, until late in their pregnancy. Playing catch-up, I counseled these soon-to-be moms about the importance of maintaining a healthy diet, for both themselves and their unborn children.

A key element of my care was to monitor each woman's weight, blood pressure, CBC, and blood-sugar levels. My goal was to keep these four cornerstones of prenatal health within a normal range. Specifically, I tried to maintain their hemoglobin level in the 11-12 range, using iron pills to supplement their dietary intake if necessary. A hemoglobin level below 10 heightened my concern, because it confirmed the diagnosis of anemia.

© 2004 Penguin, a division of Penguin Putnam, used by permission.

Tags: Sex and Romance

About the Author

Leonard Shlain is the author of Art & Physics: Parallel Visions in Space, Time & Light, and The Alphabet Versus the Goddess: The Conflict Between Word and Image. He is the chief of laparoscopic surgery at California Medical Center in San Francisco.