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  2. THE MOSAIC IMAGINATION

  UNDERSTANDING THE "FEMALE" CHROMOSOME

  KEITH AND ADELE fought all the time, like a pair of tomcats, like two drunken lumberjacks. Keith would find grist for the arguments in his reading. He read widely and thirstily, and sometimes he would come across a stray fact that fed his theorizing about the natural cosmology of male and female. Males are the seekers, he had decided, the strugglers and the creators; they build all that we see around us, the artifactual world of towering cities and invented divinity, yet they suffer for their brilliance and busyness. Females are the stabilizers, the salve for man's impatient expansionism, the mortar between bricks. Nothing surprising there: it's a familiar dialectic, between the doers and the be-ers, the seethers and the soothers, complexity and simplicity.

  Then one day Keith read about chromosomes. He read that humans have twenty-three pairs of chromosomes and that the pairs of chromosomes are the same in men and in women, with the exception of pair number 23—the sex chromosomes. In that case, women have two X chromosomes and men have one X and one Y. Moreover, a woman's two X chromosomes look pretty much like all her other chromosomes. Chromosomes resemble Xs. Not when they're inside the cells of the body, at which point they're so squashed and snarled together they resemble nothing so much as a hair knot. But when they're taken out of the cell and combed apart for viewing under a microscope by a geneticist or a lab technician who is checking a fetus's chromosomes as part of amniocentesis, they look like fat and floppy Xs. So women have twenty-three pairs, or forty-six, of these X-shaped structures, while men have forty-five Xs and that one eccentric, the Y chromosome. The Y physically resembles the letter it was named for, being stubby and tripartite and quite distinct in shape from all the other chromosomes in the cell.

  It struck Keith that even on a microscopic level, even as inscribed in the genetic clay from which human beings are constructed, men demonstrate their edge over women. Women have as their sex chromosomes two Xs: monotony. The story we've heard before. Men have an X and a Y: diversity. Genetic innovation and an escape from primal tedium. The Y as synecdoche for creativity—for genius. And so he said to Adele, The chromosomes prove the case for male superiority. You have two Xs and hence are dull, while I have an X and a Y and am accordingly interesting.

  Neither Adele nor Keith knew much about genetics, but Adele knew enough to recognize mental manure when she smelled it. She dismissed his theory with a sneer. He grew angry at her refusal to submit to his logic. The argument escalated, as their arguments always did. Keith wasn't talking about all men, of course, but about himself. He was insisting that his needs and insights took precedence over Adele's, and that she acknowledge as much. She refused to surrender.

  Of the many arguments that my parents had in the theater of our apartment before the reluctant audience of their children, this is the only one whose substance I remember. The clash of the century, Y versus X. I remember it in part because it seemed so oddly theoretical, and because it was the first time I heard an argument put forth for all-around, across-the-board male dominance. I took it personally. My feelings were hurt. It was one thing for my father to attack my mother—that I was accustomed to. But there he was, describing all females, including me, as chromosomal bores.

  The chromosome case remains very much open, a source of irritation and debate. In some ways, sex is fundamentally determined by the sex chromosomes. If you're female, you're assumed to have a pair of Xs tucked into just about every cell of your body, along with a set of those twenty-two other pairs of chromosomes. If you're a male, you know of your Y and you just might be proud of it, as your molecular phallus, and for the koanic wordplay of it: Y? Why? Why? Y! The sex chromosomes tell a technician—and you the parent, if you choose to know—whether the fetus under scrutiny in an amniocentesis screen is a girl or a boy.

  So in one sense the demarcation between X and Y is clear, clean, an inarguable separation between femaleness and maleness. And my father was right about the predictability and monochromaticity of the female chromosomal complement. Not only will you find two X chromosomes in every body cell of a woman, from the cells that line the fallopian tubes to the cells in the liver and brain, but break open an egg cell and look within the nucleus, and you'll find one X chromosome in each (again with the other twenty-two chromosomes). It is indeed the sperm cell that can add diversity to an embryo, and that determines the embryo's sex by delivering either another X, to create a female, or a Y chromosome, to make a male. X marks the egg. An egg never has a Y chromosome within it. An ejaculate of sperm is bisexual, offering a more or less equal number of female and male whip-tailed sperm, but eggs are inherently female. So in thinking again about the mirrors into infinity, the link between mother and daughter, the nesting of eggs within woman within eggs, we can go a step further and see the continuity of the chromosomes. No maleness tints any part of us gals, no, not a molar drop or quantum.*

  But of course it is not that simple. We are not that simple, appealing though the idea of a molecularly untainted matriline may be. Let us consider the nature of the sex chromosomes, the X counterpoised against the Y. To begin with, the X is bigger, much, much bigger, both in sheer size and in density of information. The X chromosome is in fact one of the largest of the twenty-three chromosomes that humans cart around, and is about six times larger than the Y, which is among the tiniest of the lot (and it would be the smallest of all if it didn't have some nonfunctional stuffing added to it just to keep it stable). Gentlemen, I'm afraid it's true: size does make a difference.

  In addition, many more genes are strung along the female chromosome than along its counterpart, and it is as a shoetree for genes that a chromosome takes on its meaning. Nobody knows exactly how many genes sit on either the X or the Y chromosome; nobody yet knows how many genes, in total, a human being has. Estimates range from 68,000 to 100,000. What is incontestable, though, is the vastly higher gene richness of the X than of the Y. The male chromosome is a depauperated little stump, home to perhaps two dozen, three dozen genes, and that's the range scientists come up with when they're feeling generous. On the X, we will find thousands of genes, anywhere from 3,500 to 6,000.

  What does this mean to us women? Are we the mother load of genes, so to speak? After all, if we have two Xs, and each X holds about 5,000 genes, whereas a man has but one X with 5,000 genes and a Y with its 30 genes, then you don't even need a calculator to figure that we should have about 4,970 more genes than a man. So why on Gaia are men bodily bigger than we are? The answer is among the neat twists of genetics: all those extra genes are just sitting around doing nothing, and that's just the way we want them. In fact, if they were all doing something, we'd be dead. Here is what I love about a female's X chromosomes: they are unpredictable. They do surprising things. They do not act like any of the other chromosomes in the body. As we shall see, to the extent that chromosomes can be said to have manners, the X chromosomes behave with great courtesy.

  Esmeralda, Rosa, and Maria live in Zacatecas, Mexico, a village of 10,000 people that, though obscure to Americans north of the border, is big enough to be a center for the smaller and more obscure towns around it. Many people in Zacatecas earn their living picking chilis and packing them up for export. Esmeralda and Rosa are sisters; both in their teens, and Maria, two years old, is their niece. * They share an extremely rare condition, so rare that their extended family may be the only people in the world to carry it. Called generalized congenital hypertrichosis, the syndrome is an atavism, a throwback to our ancient mammalian state, when we were happily covered in homegrown fur and had no need of sweatshops and Calvin Klein's soft-core porn. The term hypertrichosis explains all, trichosis meaning hair growth, and hyper meaning exactly what it says.

  Atavisms result when a normally dormant gene from our prehistoric roots is for some reason reactivated. Atavisms remind us, in the most palpable and surreal manner possible, of our bonds with other species. They tell us that evolution, like the pueblo builders of the
Southwest, does not obliterate what came before but builds on top of and around it. Atavisms are not uncommon. Some people possess an extra nipple or two beyond the usual pair, a souvenir of the ridge of mammary tissue that extends from the top of the shoulder down to the hips and that in most mammals terminates in multiple teats. Babies on occasion are born with small tails or with webbing between their fingers, as though they are reluctant to leave the forest or the seas.

  In the case of congenital hypertrichosis, a gene that fosters the generous growth of hair across the face and body has been rekindled. Nothing else happens out of the ordinary, no skeletal deformities or mental retardation or any of the other sorrows that often accompany a genetic change. The people with the condition, this large and locally renowned family living on the border of Zacatecas, simply grow a kind of pelt. They make you wonder why human beings ever shed their fur in the first place, a puzzle that evolutionary biologists have yet to crack. And despite your nobler sentiments, they also make you think of werewolves. In fact, historians of myth have suggested that conditions like hypertrichosis—other types of excess hirsutism exist beyond this rare mutation—gave rise to the legend of the werewolf.

  Another element of the werewolf story resonates with the case of Esmeralda, Rosa, and Maria. As you may recall, the werewolf crosses over to his bristly alter ego on a night of a full moon only gradually. At ten P.M., the first anomalous whiskers begin clouding the sides of his face. At eleven, the hair has crept down his forehead and across his cheeks. By midnight, the coverage has become complete, and he is free to explore his nocturnal appetites. The girls of Zacatecas are like points on the werewolf's clock. Esmeralda, who at seventeen is the eldest, is barely ten o'clock. You can see patches of dark downy hair at the edges of her chin and cheeks and around the ear area, almost as though she were standing in the shadows beneath the brutal sun of summer. It's enough to mark her as a member of her rare tribe, but not enough to inhibit her verve or keep her from dating a handsome selection of boys.

  Maria, the toddler, stands at the eleven o'clock mark. Her cheeks, her chin, and the top of her forehead are streaked with dark, fine, slightly wavy hair, which will darken and thicken with age. She looks as though she has bangs growing up from her eyebrows toward the scalp. Her eyes are dark and bright and full of joy. She has not yet learned to feel shame.

  Rosa, fifteen years old, nearly qualifies as the werewolf at midnight. Much of her face—the cheeks, chin, forehead, nose—is covered by hair; there is far more hair than skin to be seen. She is in fact hairier than a chimpanzee or a gorilla, both of which lack hair around the cheeks, nose, and eyes. Luis Figuera, of the University of Guadalajara, who is studying hypertrichosis, told me that when he first met Rosa he was startled by her appearance, but that after talking with her for a while he stopped noticing it. Eventually, he felt confident enough to ask her if he could touch her face, and she agreed. "It was like stroking the head of a baby," he said. "It was like petting a cat." Rosa's facial hair is thicker than that of any other female in her family. It is almost as dense as that of some of her male relatives, in whom the congenital condition finds its fullest expression. Two of the men earn their living in circus sideshows, where they are displayed as "dog men" or "people of the forest." Others shave their entire face, twice a day. Neither Rosa nor her older sister shaves; they are afraid that shaving will make the hair grow back coarser and darker. Instead, Rosa keeps herself largely hidden from the world. When she's not in school or at the marketplace, she stays indoors. She prefers to keep the shutters closed. She is gentle and shy and doesn't expect to have much of a social or love life.

  People commonly dream about being caught naked in public, and they wake up embarrassed. I imagine Rosa dreaming of losing her hair, every last dark muffling lock on her body. In her dreams she is neither ashamed nor afraid, but instead feels free, able to float above the flesh of earth and fate, her upturned face as smooth as a stone.

  The spectrum of hair growth seen on the girls of Zacatecas illustrates an outstanding feature of female heritage. My father thought the male had the edge in variation, the chromosomal complexity. To the contrary. It is the woman who is the greater mosaic, a patchwork of her past. Every person has two copies of each of the twenty-three chromosomes, one from mother, one from father. For twenty-two sets of those chromosomes, both versions operate. They make us who we are, an idiosyncratic porridge of our parents—his Roman nose, her rotten teeth, the worst and best of their mediocrities and charms.

  For us women, something different from the rest of our genetic legacy happens to our sex chromosomes. The two X chromosomes come together in the formation of the embryo, and as with all the chromosomes, copies of each are apportioned to each cell of the growing baby. But then, during our embryonic unfolding, each cell makes its own decision; do we want Mom, or do we prefer Father? Will we keep the maternal X chromosome active, or the paternal? Once the decision is made—and usually it is made randomly—the cell shuts down the other X, snaps it off chemically. It is a dramatic event, the shutting down of thousands and thousands of genes aligned along the entire length of a chromosome. It is like one of the great New York City blackouts, when thousands of brilliantly lit buildings suddenly blinked off. Click! cries a liver cell. There goes mother love! But then a brain cell makes up its mind, and the maternal chromosome is kept alive while the father X is nullified. Not every gene is shut off on the so-called inactivated X; a few stay lit, to match the handful of genes found on the male's dwarf of a Y chromosome. Nevertheless, thousands of genes are dispensed within a given cell, and they are either thousands from the mother or thousands from the father.

  So we can understand why the hirsute girls demonstrated such outstanding discrepancies in appearance. The gene behind congenital hypertrichosis, the atavism that once helped lend us a mammalian mantle, is located on the X chromosome. In most of us, the gene doesn't operate. The shaggy look does not suit human aesthetics, it doesn't do much to attract a mate, and so the gene has fallen fallow. But in the family with hypertrichosis, the gene has risen from its coma. It works. It makes a kind of fur. Each of the girls has inherited one copy of the fully awakened gene, Esmeralda and Rosa from their mother, niece Maria from her father. And each child is a mosaic of X chromosomes with the trait and X chromosomes without. Esmeralda's face is thus largely the face of her father, he of the unaffected X. Just by chance, the vast majority of the follicle cells on her cheeks, forehead, nose, and chin switched off the maternal X chromosome, allowing the unaffected paternal chromosome to dominate her appearance and thus keep the mark of the werewolf at bay. Her sister's face took nearly the opposite path, the cells switching off the paternal chromosome and putting the woolly maternal X to work. Maria ended up with six of one, half a dozen of the other. All was chance, all was a crapshoot. The switching pattern of the chromosomes could as easily have gone the other way for the sisters; and indeed, if they themselves have daughters, the child of the merry popular one could prove to have cheeks that feel to the touch like the face of a cat.

  The world may not make it out so easily, but we are all of us gals strange little quilts, patches of father-tone in some of our tissues, shades of mother in the others. We are more motley by far than our brothers. A son, in fact, may rightfully be thought of as a mama's boy: he has her X chromosome alive in every cell of his body. He has no choice—it's the only X he's got, and every cell needs it. Thus he has more of his mother's genes operating in his body than he does of his father's, thousands more. Yes, the Y chromosome is there, and that is solely a father-to-son transaction; but remember that the Y is genetically impoverished compared to the X. If you do the calculations, your brother works out to be about 6 percent more related to your mother than to your father, and he is 3 percent more related to your mother than you are, because half your cells, on average, have the mother chromosome turned off, while all of his remain turned on. These are not inconsequential figures. In a way, I'm sorry to mention them. They disrupt the image of the
matriline, of our female connectedness to the ancestral parade of mother, grandmother, great-grandmother, the blessed founding matriarch. (On an interesting side note, male identical twins are more identical than female twins, again as a result of X inactivation. Male twins share the totality of their maternal X chromosomes, as well as having all the other chromosomes in common, but female twins have a diverging patchwork of maternal and paternal X chromosomes operating in different parts of their bodies.)

  Men, perhaps, will be hardly more delighted at the thought of their maternal vinculum. Don't men want so badly to individuate, to pull away from the omnipotent female who dominated their world for the first fragile years of their lives? And then to find out that she is more a part of them than they thought! I know my father would not be pleased. He felt smothered by his mother, in all the classic ways. People would tell him, You should read D. H. Lawrence—you'll identify with the story of him and his mother! And my father would say, Why should I read about it? I lived it, and that was bad enough.

  In lieu of another link to the matriline I offer this enchanting thought: we have, with our female quilts, with the mosaicism of our chromosomes, a potential for considerable brain complexity. Admittedly, the claim requires a leap of faith and fancy, but let's try it anyway. To begin with, think of the X chromosome as the Smart Chromosome. I suggest this not out of simple chauvinism—although I am a female chauvinist sow—but because a preponderance of genes situated on the X chromosome seem to be involved in the blooming of the brain. Studies suggest that mutations in the X chromosome are a frequent cause of mental retardation, a more frequent cause than mutations in any of the other twenty-two chromosomes. The corollary of all that retardation is brilliant: if so many things can go wrong with our favorite chromosome to result in mental deficiency, that means it holds an awful lot of important targets—genes necessary for the construction of intelligence. When one or more of those genes fail, brain development falters, and when all hum in harmony, genius is born.