The Body, page 31
Had the importance of her discovery been more widely appreciated, Stevens would almost certainly have won a Nobel Prize. Instead, for many years the credit was usually given to Edmund Beecher Wilson, who had independently made the same discovery at almost the same time (exactly who was first has long been a matter of contention) but without fully appreciating its significance. Stevens doubtless would have achieved greater things still, but she contracted breast cancer and died aged just fifty in 1912 after only eight years as a qualified scientist.
In illustrations, the X and Y chromosomes are always portrayed as being roughly in the shape of an X or a Y, but in fact most of the time they don’t look like any letters of the alphabet. During cell division, the X chromosome does indeed briefly assume an X shape, but then so do all the non-sex chromosomes. The Y chromosome only superficially resembles a Y. It is just an extraordinary coincidence that they bear a passing or occasional resemblance to the letters for which they are named.
Historically, chromosomes were not at all easy to study. They spend most of their existence balled up in an indistinguishable mass in the cell nucleus. The only way to count them was to get fresh samples from living cells at the moment of cell division, and that was a tall order. Cell biologists, according to one report, “literally waited at the foot of the gallows in order to fix the testis of an executed criminal immediately after death before the chromosomes could clump.” Even then the chromosomes tended to overlap and blur, making anything but a rough count difficult. But in 1921, a cytologist at the University of Texas named Theophilus Painter announced that he had secured good images and declared with reassuring confidence that he had counted twenty-four pairs of chromosomes. That number stuck, universally unquestioned, for thirty-five years until a closer examination in 1956 showed that in fact we have just twenty-three pairs—a fact that had been clearly evident in photographs for years (including in at least one popular textbook illustration) had anyone taken the trouble to count.
As to what precisely makes some of us males and some females, that knowledge is even more recent. It wasn’t until 1990 that two teams in London, at the National Institute for Medical Research and at the Imperial Cancer Research Fund, identified a sex-determining region on the Y chromosome that they dubbed the SRY gene, for “sex-determining region Y.” After countless generations of making little boys and little girls, humans finally knew how they did it.
The Y chromosome is a curious and runty thing. It has only about seventy genes; other chromosomes have as many as two thousand. The Y chromosome has been shrinking for 160 million years. At its current rate of deterioration, it has been estimated, it could vanish altogether in another 4.6 million years. That doesn’t mean, happily, that males will cease to exist in 4.6 million years. The genes that determine gender traits would probably just move across to another chromosome. Moreover, our ability to manipulate the reproductive process is likely to be rather more refined in 4.6 million years, so this is probably not something we should lose sleep over.*2
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Interestingly, sex isn’t actually necessary. Quite a number of organisms have abandoned it. Geckos, the little green lizards that are often encountered clinging like suckered bath toys to walls in the tropics, have done away with males altogether. It is a slightly unsettling thought if you are a man, but what we bring to the procreative party is easily dispensed with. Geckos produce eggs, which are clones of the mother, and these grow into a new generation of geckos. From the mother’s point of view, this is an excellent arrangement because it means that 100 percent of her genes are inherited. With conventional sex, each partner passes on just half its genes, and that number is relentlessly thinned with each succeeding generation. Your grandchildren have only a quarter of your genes, your great-grandchildren only an eighth, your great-great-grandchildren a mere sixteenth, and so shrinkingly on it goes. If genetic immortality is your ambition, then sex is a very poor way of achieving it. As Siddhartha Mukherjee observed in The Gene: An Intimate History, humans don’t actually reproduce at all. Geckos reproduce; we recombine.
Sex may dilute our personal contribution to posterity, but it is great for the species. By mixing and matching genes, we get variety and that gives us safety and resilience. It makes it harder for diseases to sweep through whole populations. It also means that we can evolve. We can hold on to beneficial genes and discard ones that impede our collective happiness. Cloning gives you the same thing over and over. Sex gives you Einstein and Rembrandt—and a lot of dorks, too, of course.
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Probably no area of human existence has generated less certainty, or been more inhibitive to open discussion, than sex. Perhaps nothing says more about our delicacy toward matters genital than that the word “pudendum”—meaning the external genitals, particularly those of a woman—comes from the Latin for “to be ashamed.” It is next to impossible to get reliable figures about almost anything to do with sex as a pastime. How many people are unfaithful to their partners at some point in a relationship? Somewhere between 20 percent and 70 percent, depending on which of many studies you consult.
One problem, which should surprise no one, is that survey respondents are inclined to embrace alternative realities when they think their answers cannot be checked. In one study, the number of sexual partners women were prepared to recall increased by 30 percent when they thought they were hooked up to a lie detector. Remarkably, for a 1995 survey called the Social Organization of Sexuality: Sexual Practices in the United States, conducted jointly by the University of Chicago and the National Opinion Research Center, respondents were permitted to have someone else, usually a child or current sexual partner, present when they were interviewed, which is hardly likely to have resulted in fully candid responses. Indeed, it was shown afterward that the proportion of people answering that they had had sex with more than one person in the previous year fell from 17 percent to 5 percent when another person was present.
The survey was criticized for lots of other deficiencies. Because of funding problems, only 3,432 people were interviewed instead of the 20,000 originally intended, and because all the respondents were aged eighteen or older, it offered no conclusions on teenage pregnancies or birth control practices, or much else of crucial importance to public policy. Moreover, the survey focused only on households, so it excluded people in institutions—college students, prisoners, and members of the armed forces most notably. All of these made the report’s findings questionable if not entirely useless.
Another problem with sex surveys—and there is no delicate way of putting this—is that people are sometimes just stupid. In another analysis, reported by Cambridge University’s David Spiegelhalter in the wonderful Sex by Numbers: The Statistics of Sexual Behaviour, when asked to state what in their view constituted full sex, some 2 percent of male respondents said that penetrative intercourse did not qualify, leaving Spiegelhalter to wonder what exactly they might be waiting for “before they feel they have gone all the way.”
Because of the difficulties, the field of sex studies has a long history of providing dubious statistics. In his 1948 work, Sexual Behavior in the Human Male, Alfred Kinsey of Indiana University reported that nearly 40 percent of men had had a homosexual experience resulting in orgasm and that nearly a fifth of young men brought up on farms had had sex with livestock. Both figures are now thought highly unlikely. Even more dubious were the 1976 Hite Report on Female Sexuality and the companion Hite Report on Male Sexuality published soon afterward. The author, Shere Hite, used questionnaires and had a very low, nonrandom, highly selective response rate. Nonetheless, Hite confidently declared that 84 percent of women were dissatisfied with their male partners and that 70 percent of women married for more than five years were in an adulterous relationship. The findings were heavily criticized at the time, but the books were huge best sellers. (A more scientific, and more recent, U.S. National Health and Social Life Survey found that 15 percent of married women and 25 percent of married men said they had been unfaithful at some time.)
On top of all that, the subject of sex is full of statements and statistics that are often repeated but based on nothing. Two durable ones are these: “Men think of sex every seven seconds” and “The average amount of time spent kissing in a lifetime is 20,160 minutes” (that is 336 hours). In fact, according to genuine studies, men of college age think about sex nineteen times a day, roughly once every waking hour, which is about the same frequency as they think about food. College women think about food more often than they think about sex, but they don’t think about either terribly often. No one does anything at all every seven seconds other than perhaps respire and blink. Similarly, no one knows how much of an average lifetime is devoted to kissing or where that weirdly precise and durable figure of 20,160 minutes comes from.
On a more positive note, we can say with some confidence that the median time for sex (in Britain at least) is nine minutes, though the whole act, including foreplay and undressing, is more like twenty-five minutes. According to Spiegelhalter, energy use on average per sexual session is about a hundred calories for men and about seventy for women. A meta-analysis showed that for older people the risk of a heart attack was raised for up to three hours after sex, but it was similarly raised for shoveling snow, and sex is more fun than shoveling snow.
II
IT IS SOMETIMES said there are more genetic differences between men and women than there are between humans and chimpanzees. Well, perhaps. It all depends on how you measure genetic differences. But the statement is in any case clearly meaningless in any practical sense. A chimpanzee and a human may have as much as 98.8 percent of genes in common (depending on how they are measured), but that doesn’t mean they are just 1.2 percent different as beings. Chimpanzees cannot hold a conversation, cook dinner, or outwit a human four-year-old. Clearly, it is a question of not what genes you have but how they are expressed—how they are put to use.
That said, men and women unquestionably are very unalike in many important ways. Women (and we are talking here about healthy, fit women) carry about 50 percent more fat on their frames than fit, healthy men. This not only makes the woman more agreeably soft and shapely to suitors but also gives her reserves of fat she can call upon for milk production during times of hardship. Women’s bones wear out sooner, particularly after menopause, so they suffer more breaks in later life. Women get Alzheimer’s twice as often (partly because they also live longer) and experience higher rates of autoimmune diseases. They metabolize alcohol differently, which means they get intoxicated more easily and succumb to alcohol-related diseases like cirrhosis faster than men do.
Women even tend to carry bags differently than men do. It is thought that their wider hips necessitate a less perpendicular carrying angle for their forearm so that their swinging arms aren’t constantly banging against their legs. That’s why women generally carry bags with their palms facing forward (allowing their arms to be slightly splayed) while men carry them with palms facing back. Far more significantly, women and men have heart attacks in quite different ways. A woman suffering a heart attack is more likely to experience abdominal pain and nausea than a man, which makes it more probable that it will be misdiagnosed. In a thousand ways large and small, they are quite different beings.
Men have their own differences. They get Parkinson’s disease more often and commit suicide more, even though they suffer less from clinical depression. They are more vulnerable to infection than females (and not just humans but across nearly all species). That may indicate some hormonal or chromosomal difference that hasn’t yet been determined, or it may simply be that males on the whole lead riskier, more infection-prone lives. Men are also more likely to die from their infections and from physical injury, though again whether that is because we are hormonally compromised or just too proud and foolish to seek medical attention promptly (or both) is an unanswerable question.
All this is important because until recently drug trials very often excluded women, largely because it was feared their menstrual cycles could skew results. As Judith Mank of University College London told the BBC program Inside Science in 2017, “People had been assuming that women are just 20 percent smaller than men, but otherwise are much the same.” We now know that there is much more to it than that. In 2007, the journal Pain reviewed all of its published findings over the previous decade and found that almost 80 percent had come from male-only tests. A similar gender bias, based on hundreds of clinical studies, was reported for cancer trials in the journal Cancer in 2009. Such findings are seriously consequential because women and men can respond to drugs in very different ways—ways often overlooked by clinical trials. The drug phenylpropanolamine was commonly used in over-the-counter medications for colds and coughs for years until it was discovered that it appreciably increased the risk of hemorrhagic stroke in women but not in men. Similarly, an antihistamine called Hismanal and an appetite suppressant called Pondimin were withdrawn after they were shown to pose serious risks to women, but only after the first had been on the market for eleven years and the second for twenty-four. Ambien, a popular sleep medication in America, had its recommended dosage for women cut in half in 2013 when it was found that a high proportion of female users were suffering impaired performance if they tried to drive the next morning. Men did not suffer in anything like the same way.
Women are anatomically different in one other very significant way: they are the sacred keepers of human mitochondria—the vital little powerhouses of our cells. Sperm pass on none of their mitochondria during conception, so all mitochondrial information is transferred from generation to generation through mothers alone. Such a system means that there will be many extinctions along the way. A woman endows all her children with her mitochondria, but only her daughters have the mechanism to pass it onward to future generations. So if a woman has only sons or no children at all—and that happens quite often, of course—her personal mitochondrial line will die with her. All her descendants will still have mitochondria, but it will come from other mothers on other genetic lines. In consequence, the human mitochondrial pool shrinks a little with every generation because of these localized extinctions. Over time, the mitochondrial pool for humans has shrunk so much that, almost unbelievably but rather wonderfully, we are all now descended from a single mitochondrial ancestor—a woman who lived in Africa about 200,000 years ago. You might have heard her referred to as Mitochondrial Eve. She is, in a sense, mother of us all.
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For most of recorded history, we have known shockingly little about women and how they are put together. As Mary Roach notes in her delightfully irreverent book Bonk, “Vaginal secretions [were] the only bodily fluid about which virtually nothing was known” despite their importance to conception and a woman’s general sense of well-being.
Matters specific to women—menstruation above all—were almost totally a mystery to medical science. Menopause, clearly another milestone event in a woman’s life, didn’t attract formal notice until 1858, when the word is first recorded in English, in the Virginia Medical Journal. Abdominal examinations were conducted rarely, vaginal examinations almost never, and any investigations below the neck usually involved the doctor feeling blindly under the bedclothes while gazing fixedly at the ceiling. Many doctors kept dummies so that a woman could point to the affected part without having to reveal or even mention it by name. When René Laënnec invented the stethoscope in 1816 in Paris, the greatest benefit wasn’t that it improved sound transmission (an ear to the chest was actually about as good) but that it allowed a physician to check a woman’s heart and other inner workings without directly touching her flesh.
Even now, there is a huge amount concerning female anatomy about which we are uncertain. Consider the G spot. It is named for Ernst Gräfenberg, a German gynecologist and scientist who fled Nazi Germany for America and there developed the intrauterine contraceptive device, which was originally called the Gräfenberg ring. In 1944, he wrote an article for the Western Journal of Surgery, Obstetrics and Gynecology in which he identified an erogenous spot on the wall of the vagina. The Western Journal of Surgery, Obstetrics and Gynecology did not normally attract a great deal of attention, but this article got passed around. Thanks to it, the newly identified erogenous location became known as the Gräfenberg spot, subsequently shortened to G spot. But whether or not women actually possess a G spot is a matter of continuing, and sometimes heated, debate. Imagine the amount of research funding that would follow if someone were to suggest that males have an erogenous spot that they have not been fully utilizing. In 2001, the American Journal of Obstetrics and Gynecology declared the G spot a “modern gynecologic myth,” but other studies have shown that a majority of women, in America at least, believe they have one.
Male ignorance of female anatomy is quite arresting, it appears, particularly when you consider how keen men are to get to know it in other respects. A survey of a thousand men, conducted in conjunction with a campaign called Gynecological Cancer Awareness Month, found that the majority could not reliably define or identify most of a female’s private parts—vulva, clitoris, labia, and so on. Half could not even find the vagina on a diagram. So perhaps a brief rundown is in order here.
The vulva is the complete genital package—vaginal opening, labia, clitoris, and so on. The fleshy mound above the vulva is called the mons pubis. At the top of the vulva itself is the clitoris (probably from a Greek word for “hillock,” but there are other candidates), which is packed with some eight thousand nerve endings—more per unit of area than any other part of the female anatomy—and exists, as far as can be told, only to give pleasure. Most people, including females, are unaware that the visible part of the clitoris, called the glans, is literally only the tip of it. The rest of the clitoris plunges into the interior and extends down both sides of the vagina for about five inches. Until the early twentieth century, “clitoris” seems generally to have been pronounced “kly-to-rus.”
