Iron / Sex, Part 3

Sex, Time, and Power: How Women's Sexuality Shaped Human Evolution
by Leonard Shlain, M.D.

(Page 3 of 6)

These musings have convinced me that significant differences in iron levels between the sexes were the initial driving force behind many uniquely human cultural innovations. I shall trace the connections of art, calendars, marriage, mayhem, fatherhood, and homosexuality, to name but a few, back to this arcane feature of human physiology. Along the journey, I shall also explore the links between the moon and menses, sex and death, and funerals and paternity.

Throughout my life, I have maintained a lively interest in matters relating to life-forms and evolutionary theory. As a premed undergraduate learning the wondrous stages of embryology or comparing the anatomy of differing species, I recall having moments of pure rapture whenever I grasped the intricacies behind some aspect of the breathtaking beauty of life. The study of its sumptuous diversity is, for me, the quintessential melding of science and aesthetics. I still marvel over the improbability of a caterpillar's metamorphosis, the texture of a calla lily's singular petal, or the amazing grace of a formation of pelicans skimming waves. I will try to infuse this book with my sense of awe and enthusiasm for the processes of life while I elaborate my theories on the bonding glue that holds human relationships together.

Some might wonder why a surgeon would dare to wander so far from his field of specialized expertise to enter the bramble-ridden thicket of human sexuality. The simple answer: It fascinates me, as, I suspect, it does you. And I believe I have some fresh insights to contribute to the subject.

My direct experience with matters relating to physiology, anatomy, biochemistry, and psychology, essential to my training as a physician and surgeon, has served me well in researching this book. My knowledge of anthropology, primatology, evolutionary biology, and archeology is the result of my abiding interest in these fields. However, I must admit at the outset that I am not an expert in all the fields into which I delve.

Sex, Time, and Power is intended for both generalists and specialists. Although it is based on scientific research and theories, I wish to keep to a minimum the standard academic practice of citing the pedigree of a particular idea by listing the numerous authorities who were involved in its lineage. I do not wish to diminish these innovators, but I also do not want the book to read too much like a textbook. I also will resist the temptation, whenever possible, to use arcane zoological names, or to cite daunting statistics.

Space requirements imposed by the publishing world prevent me from presenting every alternative theory to the ones I propose. This does not necessarily mean that I am unaware or dismissive of other possibilities, but, in a bow to the wordsmith's aesthetic, I will try to keep many supporting facts, counterarguments, and authoritative references caged in the footnotes and endnotes.

One of the great pleasures I derive from writing is conjuring metaphors that can translate complex physiological and evolutionary processes into rich images, increasing an idea's accessibility for the nonspecialist reader. A key metaphor that I will employ throughout this work is to treat the process of natural selection as if it behaved like an intelligent entity with forethought and purpose. Exercising a writer's prerogative to use poetic license, I will use the terms "Mother Nature," "Natural Selection," and "the Red Queen" interchangeably.

My use of these terms, however, should not be misconstrued. I am not imputing purposeful design to a supernatural entity. Natural selection is a natural process. The origin of species does not need a deus ex machina to explain how it works.

Darwin's ideas have been put to the rigors of scientific examination for a century and a half, and although there still remain many intriguing questions, overall he has provided scientists with a powerful predictive tool. Whether or not a supernatural entity first set in motion evolution's ingenious processes of natural selection based on random mutations of genes interacting with environmental changes is a religious question better left to each reader to answer.

While on the subject of disclaimers, let me neutralize the contentious nature-versus-nurture debate at the outset. There is no gene-controlled inheritable trait that cannot be altered by the environment. Similarly, the genetic makeup of the organism can overcome the influence of the environment. Each factor can affect and alter the other. Humans enter the world as a work-in-progress. In some cases, the culture or environment into which a person is born more strongly determines his or her responses to the vagaries of life, and sometimes responses are more influenced by the genes he or she has inherited. Nature/nurture is not an either/or duality but, rather, represents a both/and type of complementarity.

I assume that the reader is reasonably familiar with the essence of Darwin's ideas, but there are two notions I feel compelled to differentiate at the outset. After Darwin electrified the intellectual world in 1859 with his theory of evolution based on natural selection, he refined it further in 1871 by emphasizing the importance of sexual selection. For, as Darwin realized, it was simply not enough that an organism survived both the rigors of competition and the hardships imposed by its environment (natural selection), it also had to reproduce successfully (sexual selection). Mate selection became a critical factor in accounting for how sexually reproducing organisms came to be the way they were. Males competed among themselves to see who won the right to mate with females. And females, by picking and choosing among myriad suitors, exerted an enormous influence on which male traits advanced in the genome. Males, therefore, tended to be what females wanted them to be. Natural Selection is about survival, and Sexual Selection concerns reproduction. I will use the term "Natural Selection" as the generic process moving evolution along, even when there may be elements of sexual selection combined within it.

Another caveat: Because the story I intend to tell unfolds in a linear, sequential narrative, it might appear that I am proposing that first one thing occurred and then that caused another to occur, with cause and effect clanking along in a prescribed sequence. This is not the case. The process of Natural Selection is a to-and-fro, give-and-take, nonlinear whorl. Ongoing, simultaneous feedback loops between local environments and individuals are the driving force compelling species to alter their shape, behavior, and metabolism. This ever-changing, continuous ebb and flow creates a fluid dynamic that linear narrative can never adequately convey.

Because I will be writing at length about matters relating to sex, birth, and death as well as the love between a man and a woman and between parents and children, I feel I should share something of my personal background in addition to my professional qualifications.

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

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.