Woman: An Intimate Geography (32 page)

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Authors: Natalie Angier

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age daughters, sisters, dorm mates, and lesbian lovers had of a mysterious coming together, of the simultaneous raiding of the tampon box, a sisterhood in the blood.
Subsequent studies of menstrual synchrony, however, were not so neat. Some confirmed the original report, others refuted it. According to one recent review of the menstrual synchrony studies published over the past twenty-five years, sixteen have found statistically significant evidence of synchrony and ten have failed to find any statistically meaningful patterns. A few studies have revealed evidence of asynchrony, or antisynchrony: as the months passed, the cohabiting women became
less
harmonized in their periods rather than more, sometimes to the point of diametric opposition. It's as though the women were signaling to each other, We had nothing in common before, so please, let's keep it that way.
McClintock is a woman of verve, rigor, and high, loopy enthusiasm who wears bright scarves over cashmere sweaters and unexpected accessories, like dove-gray socks patterned with black fishes. She explores how the environment influences physiology how nurture nudges nature. She looks, for example, at the impact of mental attitude on the course of a disease, how the belief that you
can
get well may influence whether you
do
get well. She looks at how social isolation affects health; as a rule, in social animals extended solitude affects health badly, and the questions are why and how can we measure that badness and ferret out its source, the vertex between what looks like whoo-whoo mysticism and the measurable changes in hardcore physiology. Menstrual synchrony is real, McClintock insists, but it is not the whole story. People look at menstrual synchrony and get stuck on a very narrow interpretation of it, she explained to me. They say either women's periods converge in a statistically significant manner when they live together and menstrual synchrony exists, or they don't and it's bunk.
"People focus on menstrual synchrony as the main phenomenon because it's such a compelling idea," she said. "But I can't emphasize strongly enough, it's just the left ear of the elephant. It's just one aspect of the social control of ovulation." In social creatures, she continued, fertility, ovulation, and birth occur in the context of the group. The fallopian tubes may act like little suckers, but we don't conceive or gestate in a vacuum. We are at the mercy of the tribe, and our bodies

 

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know it, and they respond accordingly. As the dynamics of the group change, so too do our reactions. To ovulate in step with our female cohorts might behoove us under one circumstance and shackle us under another. McClintock and her colleagues have found that female rats can emit pheromones that suppress fertility in other females and pheromones that enhance it. "Those pheromones can be produced at different phases of the reproductive cycle, and at pregnancy and lactation," McClintock said. "Females send out different signals depending on their state, and the females living with them respond in a variety of ways. In some cases synchrony develops, in other cases it doesn't."
The rat work has yielded a wealth of detail and gives a sense of how nuanced the conversation between ovary and society can be. As a rule, female rats in a group strive to ovulate and conceive within a week or two of one another. They keep in reasonably close gestational step so that when all is done, they can breastfeed together, in a squirming, squealing mass. They're not sweet little communists. They're Norway rats, the kind of surly, toothy scavengers you find in dumpsters and sewers. But it turns out that by pooling pups and breastfeeding duties, each female benefits. She spends less time and energy lactating than she would if she had to attend to her offspring solo, and her pups are comparatively fatter and healthier at weaning. Synchrony, then, is the optimal state. And if a female for some reason miscarries or loses her litter soon after birth, she will do what rats hate to do, which is to hold back before breeding again. She awaits signals from her lactating sister rats. She wants to reset her clock so that it synchronizes once again with theirs.
There is more to the rats' tale of how society shapes biology. If a female for some reason falls out of sync with the group and conceives pups anyway, her sense of her own procreational asynchrony has a profound effect. She ends up giving birth to a litter composed largely of daughters rather than the standard half male, half female brood of the harmonious rat. Here is what happens. The new mother rat is going to be living and breastfeeding around other females, who are on a different biodock from hers and who are thus likely to have pups that are much older than the newborn litter. Older pups are notorious milk hounds, and no milk is sweeter and more nutritious than the milk of a freshly lactating breast. They will steal much of the new mother's milk, and she

 

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can do little to prevent their nips. Therefore, many of her own helpless offspring will die of starvation. If only one or two of her pups are going to make it, it's best that they be females. Among rats (and many other species), daughters are the safe sex, sons the high-risk sex. Daughters are government bonds; sons are junk bonds. A male rat might copulate widely and madly and make scores of babies and make his mother a triumphant, wealthy grandmother, but he might fail completely and inseminate nobody and make nothing of himself or his bloodline. By contrast, it is a very rare female rat who does not breed at all. She can have only so many pups in her lifetime, but she will have some. When times are hard and prospects grim, then, invest in daughters. They will keep the lineage alive. We see here an extraordinary example of the outside elbowing its way into the deepest chambers, into the womb. The pregnant female rat senses her asynchrony, and the status of her social group and of the communal breast, and somehow she translates that sensory information into a bias against male fetuses, resorbing them into her body before they cost her a drachma of possibly fruitless care. Feeling at risk, her body seeks guarantees. It gives her girls.
In 1998, the McClintock team again published a major report in the journal
Nature
, confirming that we have a bit of the rat in us and that our ovaries too are susceptible to the sway of the Weltanschauung of the group. The scientists showed that if they took swabs from the armpits of women at different points in their ovulatory cycle and applied the swabs to the upper lips of other women, the donor secretions could act as pheromones, as odorless chemical signals. The secretions either hastened or prolonged the cycles of many, though not all, of the women exposed to them. Armpit swabs taken from women early in their cycle, in the follicular phase, before ovulation, had the effect of shortening the cycles of the recipient women that is, the beneficiaries ovulated several days earlier than predicted from prior records of their cycles. If, in contrast, the underarm swabs were taken later in the month, around the time when the donors were ovulating, the pheromones extended the cycles of the women given an upper-lip treatment the recipients ovulated several days later than predicted from their ordinary cycle span. Pheromone samples taken later still, after the donors had ovulated during the luteal phase of the cycle, which precedes menstruation had no impact on the recipients one way or another.

 

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Not all of the women were influenced by the pheromones, but enough of them were to elevate the findings to robust statistical significance and to demonstrate with fair firmness that human pheromones exist. What we see in this carefully controlled experiment is that women can push and women can pull, and they can respond to other women in varying ways, all unconsciously, without knowing why, without the benefit even of olfaction, for the women in the study said they smelled nothing when the swab was applied under their nose, save for the scent of rubbing alcohol used as a prep in the experiment. The results also explain why studies of menstrual synchrony have wandered all over the place, sometimes coming up positive and sometimes negative: because the pheromonal signals can either bring women's cycles together or push them apart, depending on when in the month the signals are produced, studies that just searched for total synchrony missed the equally important asynchronous patterns that emerged.
But what is the good of this social control of ovulation? What is the good of trying to bring other women into concert with you or trying to throw other women out of reproductive joint? We don't know. We can only speculate. We must expand our imaginations, backward, forward, and outward. We must think beyond lunar phases and simple ovulation and menstruation and take into account the months that women spend being pregnant, and the months or years they breastfeed, and the smells and cues they might emit during those protracted states. We must think as well of our emotional and political relationship to our cohabitants and the degree to which we feel camaraderie with them, or competition, or utter disinterest. If we are very comfortable with the women in our intimate domain, then menstrual synchrony might more easily emerge. To feel safe is to feel willing to risk impregnation. It is easier to conceive when ovulation is regular, and one way to entrain the cycle, to stabilize it, is to attend to the resonant frequency of those around you.
If, though, we feel at odds with our den mates, then why expect ovarian collusion, or any sort of stabilizing influence from them at all? Subordinate cotton-top monkeys will not ovulate when they are around the ruling female. The alpha female doesn't hound them. She doesn't beat them or steal food from them. Mostly she ignores them. Yet the smell or sight or aura of her muffles the subordinates' neural oscillator, and they don't ovulate. Might a woman also recoil in the presence of a

 

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threatening or irritating female? If that rival is nursing a newborn, might the woman choose to delay her own ovulation a bit unconsciously choose, of course so that when she conceives and must meet the demands of pregnancy, she will not face the additional burden of competing for resources against a hostile lactator? The social control of ovulation could be used cooperatively, then, to harmonize cycles, or it could be used defensively, to avoid conflict, or it could be used offensively, to destabilize a competitor's cycle, to attempt to undermine her fertility, if need be.
''Information is the key. It is always the key," says McClintock. "The more information one has, the better. The woman who is able to regulate and optimize her fertility, to ensure that she is fertile at the best possible time in terms of both her physical and her social environment, will be more successful than the woman who hasn't a clue." Pheromones are only one source of information, McClintock says. They are not the sole source, or even necessarily a central source, of information about where you stand and whether it's time to make your move. Pheromones simply add to the mix, and sometimes they're worth attending to and sometimes they're not and so it was that some of the women in McClintock's study were susceptible to them and some were not.
We are submerged in a sea of sensory advice. Our sexual partners exert influences of their own on our brains and baskets. Women who live with men tend to cycle in a more predictable fashion than women who live alone, and regular cycling augments the chance of conception. A woman might again be responding to pheromones, secreted by the man's armpit, his groin, or the back of his neck, at just the spot where she feels compelled to nuzzle. But why stop at the nose? Your whole body can serve as a busybody. As we saw earlier, a woman is likelier to become pregnant from sex with an adulterous lover than she is from sex with her husband. The data are under dispute and could be explained by something as mundane as the fact that a woman may be unwilling to take birth control to an assignation for fear of discovery. Alternatively, as we have seen, the discrepancy could be the result of orgasm's pulling desired sperm in, as a form of last-ditch female choice. Yet another possibility is that pleasure, like the presence of other females, can have congress with the ovaries and sway the timing of ovulation, perhaps by

 

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triggering the LH surge that liberates an egg from its cell. I strongly suspect that climax counts, and that anything capable of causing the uterus to shudder so insistently must impress the neighboring pods and their seeds as well. Maybe a follicle, on feeling the temblor, will quicken its pace of maturation and tell the brain, Hurry up, please, it's time, and the brain will respond with an LH surge, the ovum's hymn of freedom.
Admittedly, I have been seduced by experience, my personal encounter with the fertility spirits. My husband and I had been trying for years to become pregnant. I cycled like a metronome, every twenty-eight days. And for a while our sex became metronomic too, concentrated furiously around midmonth, when I thought I was likeliest to conceive. We tried all the suggested positions. Sometimes I'd have an orgasm during sex; sometimes I consciously refrained. Who knew whether a pulsing cervix would pull in the sperm or spit it out? Best to be catholic in every detail. I would lie afterward immobilized, with buttocks elevated. I used ovulation predictor kits to detect my LH surge. For several months we abided by the thin blue line. Nothing happened, nothing, nothing, nothing.
In November of 1995, my little predictor sticks failed to detect evidence of an LH surge. I was terribly glum about that: an anovulatory cycle, I thought, and there I was, thirty-seven years old, running out of time. But in December I found out that I was pregnant that I had conceived the month before, when I was certain all lay fallow. I reviewed the sequence of events, and I knew what had happened. Early in my cycle, days before I thought conception was possible, my husband and I had done what we managed so rarely in those times of procreation fixation and had sex for the pure love and pleasure of it. That act, I am sure, that pointless, magic squander, pumped up my cycle as smartly as Jan Ullrich jazzing through the Tour de France. My climax quickened the hatching of an avid egg. It provoked an LH surge, and the surge spurred a follicle, and the egg broke free and dove down a tube, and the sperm from the precipitating event was there to greet it. And everything fell into place so swiftly that by the time I started the usual midmonth screening for an LH surge, I had missed the excitement. I thought I lay fallow, but in truth I already was in clover.
I have no proof of any of this, of course. All I have is my child. A rat's distress will give her daughters. I got mine from joy.

 

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