I GREW UP IN A HOUSEHOLD where we were very suspicious of dented cans. Dented cans were, according to my mother, a well-established gateway to botulism, and botulism was a bad thing, worse than swimming immediately after lunch. It was one of those bad things measured in extinctions, as in “three tablespoons of botulism toxin could theoretically kill every human on Earth.” Or something like that.

So I refused to believe the early reports, a few years back, that socialites had begun injecting dilute strains of the toxin into their brows in an effort to temporarily remove the vertical furrow that appears between one’s eyes as one ages. It sounded like a Monty Python routine, some clinic where they daubed your soles with plague germs to combat athlete’s foot. But I was wrong to doubt. As the world now knows, Botox has become, in a few short years, a staple weapon in the cosmetic arsenal — so prevalent that, in the words of one writer, “it is now rare in certain social enclaves to see a woman over the age of thirty-five with the ability to look angry.” With their facial muscles essentially paralyzed, actresses are having trouble acting; since the treatment requires periodic booster shots, doctors warn that “you could marry a woman (or a man) with a flawlessly even face and wind up with someone who four months later looks like a Shar-Pei.” But never mind — now you can get Botoxed in strip mall storefronts and at cocktail parties.

People, in other words, will do fairly far-out things for less-than-pressing causes. And more so all the time: public approval of “aesthetic surgery” has grown fifty percent in the United States in the last decade. But why stop there? Once you accept the idea that our bodies are essentially plastic, and that it’s okay to manipulate that plastic, there’s no reason to think that consumers would balk because “genes” were involved instead of, say, “toxins.” Especially since genetic engineering would not promote your own vanity, but instead be sold as a boon to your child.

The vision of genetic engineers is to do to humans what we have already done to salmon and wheat, pine trees and tomatoes. That is, to make them better in some way; to delete, modify, or add genes in developing embryos so that the cells of the resulting person will produce proteins that make them taller and more muscular, or smarter and less aggressive, maybe handsome and possibly straight. Even happy. As early as 1993, a March of Dimes poll found that forty-three percent of Americans would engage in genetic engineering “simply to enhance their children’s looks or intelligence.”

Ethical guidelines promulgated by the scientific oversight boards so far prohibit actual attempts at human genetic engineering, but researchers have walked right to the line, maybe even stuck their toes a trifle over. In the spring of 2001, for instance, a fertility clinic in New Jersey impregnated fifteen women with embryos fashioned from their own eggs, their partner’s sperm, and a small portion of an egg donated by a second woman. The procedure was designed to work around defects in the would-be mother’s egg — but in at least two of the cases, tests showed the resulting babies carried genetic material from all three “parents.”

And so the genetic modification of humans is not only possible, it’s coming fast; a mix of technical progress and shifting mood means it could easily happen in the next few years. Consider what happened with plants. A decade ago, university research farms were growing small plots of genetically modified grain and vegetables. Sometimes activists who didn’t like what they were doing would come and rip the plants up, one by one. Then, all of a sudden in the mid-1990s, before anyone had paid any real attention, farmers had planted half the corn and soybean fields in America with transgenic seed.

Every time you turn your back this technology creeps a little closer. Gallops, actually, growing and spreading as fast as the internet. One moment you’ve sort of heard of it; the next moment it’s everywhere. But we haven’t done it yet. For the moment we remain, if barely, a fully human species. And so we have time yet to consider, to decide, to act. This is arguably the biggest decision humans will ever make.

Right up until this decade, the genes that humans carried in their bodies were exclusively the result of chance — of how the genes of the sperm and the egg, the father and the mother, combined. The only way you could intervene in the process was by choosing who you would mate with — and that was as much wishful thinking as anything else, as generation upon generation of surprised parents have discovered.

But that is changing. We now know two different methods to change human genes. The first, and less controversial, is called somatic gene therapy. Somatic gene therapy begins with an existing individual — someone with, say, cystic fibrosis. Researchers try to deliver new, modified genes to some of her cells, usually by putting the genes aboard viruses they inject into the patient, hoping that the viruses will infect the cells and thereby transmit the genes. Somatic gene therapy is, in other words, much like medicine. You take an existing patient with an existing condition, and you in essence try and convince her cells to manufacture the medicine she needs.

Germline genetic engineering on the other hand is something very novel indeed. “Germ” here refers not to microbes, but to the egg and sperm cells, the germ cells of the human being. Scientists intent on genetic engineering would probably start with a fertilized embryo a week or so old. They would tease apart the cells of that embryo, and then, selecting one, they would add to, delete, or modify some of its genes. They could also insert artificial chromosomes containing predesigned genes. They would then take the cell, place it inside an egg whose nucleus had been removed, and implant the resulting new embryo inside a woman. The embryo would, if all went according to plan, grow into a genetically engineered child. His genes would be pushing out proteins to meet the particular choices made by his parents, and by the companies and clinicians they were buying the genes from. Instead of coming solely from the combination of his parents, and thus the combination of their parents, and so on back through time, those genes could come from any other person, or any other plant or animal, or out of the thin blue sky. And once implanted they will pass to his children, and on into time.

But all this work will require one large change in our current way of doing business. Instead of making babies by making love, we will have to move conception to the laboratory. You need to have the embryo out there where you can work on it — to make the necessary copies, try to add or delete genes, and then implant the one that seems likely to turn out best. Gregory Stock, a researcher at the University of California and an apostle of the new genetic technologies, says that “the union of egg and sperm from two individuals…would be too unpredictable with intercourse.” And once you’ve got the embryo out on the lab bench, gravity disappears altogether. “Ultimately,” says Michael West, CEO of Advanced Cell Technology, the firm furthest out on the cutting edge of these technologies, “the dream of biologists is to have the sequence of DNA, the programming code of life, and to be able to edit it the way you can a document on a word processor.”

Does it sound far-fetched? We began doing it with animals (mice) in 1978, and we’ve managed the trick with most of the obvious mammals, except one. Some of the first germline interventions might be semimedical. You might, say some advocates, start by improving “visual and auditory acuity,” first to eliminate nearsightedness or prevent deafness, then to “improve artistic potential.” But why stop there? “If something has evolved elsewhere, then it is possible for us to determine its genetic basis and transfer it into the human genome,” says Princeton geneticist Lee Silver — just as we have stuck flounder genes into strawberries to keep them from freezing, and jellyfish genes into rabbits and monkeys to make them glow in the dark.

But would we actually do this? Is there any real need to raise these questions as more than curiosities, or will the schemes simply fade away on their own, ignored by the parents who are their necessary consumers?

Anyone who has entered a baby supply store in the last few years knows that even the soberest parents can be counted on to spend virtually unlimited sums in pursuit of successful offspring. What if the “Baby Einstein” video series, which immerses “learning enabled” babies in English, Spanish, Japanese, Hebrew, German, Russian, and French, could be bolstered with a little gene-tweaking to improve memory? What if the Wombsongs prenatal music system, piping in Brahms to your waiting fetus, could be supplemented with an auditory upgrade? One sociologist told The New York Times we’d crossed the line from parenting to “product development,” and even if that remark is truer in Manhattan than elsewhere, it’s not hard to imagine what such attitudes will mean across the affuent world.

Here’s one small example. In the 1980s, two drug companies were awarded patents to market human growth hormone to the few thousand American children suffering from dwarfism. The FDA thought the market would be very small, so HGH was given “orphan drug status,” a series of special market advantages designed to reward the manufacturers for taking on such an unattractive business. But within a few years, HGH had become one of the largest-selling drugs in the country, with half a billion dollars in sales. This was not because there’d been a sharp increase in the number of dwarves, but because there’d been a sharp increase in the number of parents who wanted to make their slightly short children taller. Before long the drug companies were arguing that the children in the bottom five percent of their normal height range were in fact in need of three to five shots a week of HGH. Take eleven-year-old Marco Oriti. At four foot one, he was about four inches shorter than average, and projected to eventually top out at five foot four. This was enough to convince his parents to start on a six-day-a-week HGH regimen, which will cost them $150,000 over the next four years. “You want to give your child the edge no matter what,” said his mother.

A few of the would-be parents out on the current cutting edge of the reproduction revolution — those who need to obtain sperm or eggs for in vitro fertilization — exhibit similar zeal. Ads started appearing in Ivy League college newspapers a few years ago: couples were willing to pay $50,000 for an egg, provided the donor was at least five feet, ten inches tall, white, and had scored 1400 on her SATs. There is, in other words, a market just waiting for the first clinic with a catalogue of germline modifications, a market that two California artists proved when they opened a small boutique, Gene Genies Worldwide, in a trendy part of Pasadena. Tran Kim-Trang and Karl Mihail wanted to get people thinking more deeply about these emerging technologies, so they outfitted their store with petri dishes and models of the double helix, and printed up brochures highlighting traits with genetic links: creativity, extroversion, thrill-seeking criminality. When they opened the doors, they found people ready to shell out for designer families (one man insisted he wanted the survival ability of a cockroach). The “store” was meant to be ironic, but the irony was lost on a culture so deeply consumer that this kind of manipulation seems like the obvious next step. “Generally, people refused to believe this store was an art project,” says Tran. And why not? The next store in the mall could easily have been a Botox salon.

But say you’re not ready. Say you’re perfectly happy with the prospect of a child who shares the unmodified genes of you and your partner. Say you think that manipulating the DNA of your child might be dangerous, or presumptuous, or icky? How long will you be able to hold that line if the procedure begins to spread among your neighbors? Maybe not so long as you think: if germline manipulation actually does begin, it seems likely to set off a kind of biological arms race. “Suppose parents could add thirty points to their child’s IQ,” asks MIT economist Lester Thurow. “Wouldn’t you want to do it? And if you don’t, your child will be the stupidest in the neighborhood.” That’s precisely what it might feel like to be the parent facing the choice. Individual competition more or less defines the society we’ve built, and in that context love can almost be defined as giving your kids what they need to make their way in the world. Deciding not to soup them up…well, it could come to seem like child abuse.

Of course, the problem about arms races is that you never really get anywhere. If everyone’s adding thirty IQ points, then having an IQ of one hundred fifty won’t get you any closer to Stanford than you were at the outset. The very first athlete engineered to use twice as much oxygen as the next guy will be unbeatable in the Tour de France — but in no time he’ll merely be the new standard. You’ll have to do what he did to be in the race, but your upgrades won’t put you ahead, merely back on a level playing field. You might be able to argue that society as a whole was helped, because there was more total brainpower at work, but your kid won’t be any closer to the top of the pack. All you’ll be able to do is guarantee she won’t be left hopelessly far behind.

In fact, the arms-race problem has an extra ironic twist when it comes to genetic manipulation. The United States and the Soviet Union could, and did, keep adding new weapons to their arsenals over the decades. But with germline manipulation, you get only one shot; the extra chromosome you stick in your kid when he’s born is the one he carries throughout his life. So let’s say baby Sophie has a state-of-the-art gene job: her parents paid for the proteins discovered by, say, 2005 that, on average, yielded ten extra IQ points. By the time Sophie is five, though, scientists will doubtless have discovered ten more genes linked to intelligence. Now anyone with a platinum card can get twenty IQ points, not to mention a memory boost and a permanent wrinkle-free brow. So by the time Sophie is twenty-five and in the job market, she’s already more or less obsolete — the kids coming out of college just plain have better hardware.

“For all his billions, Bill Gates could not have purchased a single genetic enhancement for his son Rory John,” writes Gregory Stock, at the University of California. “And you can bet that any enhancements a billion dollars can buy Rory’s child in 2030 will seem crude alongside those available for modest sums in 2060.” It’s not, he adds, “so different from upgraded software. You’ll want the new release.”

The vision of one’s child as a nearly useless copy of Windows 95 should make parents fight like hell to make sure we never get started down this path. But the vision gets lost easily in the gushing excitement about “improving” the opportunities for our kids.

Beginning the hour my daughter came home from the hospital, I spent part of every day with her in the woods out back, showing her trees and ferns and chipmunks and frogs. One of her very first words was “birch,” and you couldn’t have asked for a prouder papa. She got her middle name from the mountain we see out the window; for her fifth birthday she got her own child-sized canoe; her school wardrobe may not be relentlessly up-to-date but she’s never lacked for hiking boots. As I write these words, she’s spending her first summer at sleep-away camp, one we chose because the kids sleep in tents and spend days in the mountains. All of which is to say that I have done everything in my power to try and mold her into a lover of the natural world. That is where my deepest satisfactions lie, and I want the same for her. It seems benign enough, but it has its drawbacks; it means less time and money and energy for trips to the city and music lessons and so forth. As time goes on and she develops stronger opinions of her own, I yield more and more, but I keep trying to stack the deck, to nudge her in the direction that’s meant something to me. On a Saturday morning, when the question comes up of what to do, the very first words out of my mouth always involve yet another hike. I can’t help myself.

In other words, we already “engineer” our offspring in some sense of the word: we do our best, and often our worst, to steer them in particular directions. And our worst can be pretty bad. We all know people whose lives were blighted trying to meet the expectations of their parents. We’ve all seen the crazed devotion to getting kids into the right schools, the right professions, the right income brackets. Parents try and pass down their prejudices, their politics, their attitude toward the world (“we’ve got to toughen that kid up — he’s going to get walked all over”). There are fathers who start teaching the curveball at the age of four, and sons made to feel worthless if they don’t make the Little League traveling team. People move house so that their kids can grow up with the right kind of schoolmates. They threaten to disown them for marrying African Americans, or for not marrying African Americans. No dictator anywhere has ever tried to rule his subjects with as much attention to detail as the average modern parent.

Why not take this just one small step further? Why not engineer children to up the odds that all that nudging will stick? In the words of Lee Silver, the Princeton geneticist, “Why not seize this power? Why not control what has been left to chance in the past? Indeed, we control all other aspects of our children’s lives and identities through powerful social and environmental influences…. On what basis can we reject positive genetic influences on a person’s essence when we accept the rights of parents to benefit their children in every other way?” If you can buy your kid three years at Deerfield, four at Harvard, and three more at Harvard Law, why shouldn”t you be able to turbocharge his IQ a bit?

But most likely the answer has already occurred to you as well. Because you know plenty of people who managed to rebel successfully against whatever agenda their parents laid out for them, or who took that agenda and bent it to fit their own particular personality. In our society that’s often what growing up is all about — the sometimes excruciatingly diffcult, frequently liberating break with the expectations of your parents. The decision to join the Peace Corps (or, the decision to leave the commune where you grew up and go to business school). The discovery that you were happiest davening in an Orthodox shul three hours a day, much to the consternation of your good suburban parents who almost always made it to Yom Kippur services; the decision that, much as you respected the Southern Baptist piety of your parents, the Bible won’t be your watchword.

Without the grounding offered by tradition, the search for the “authentic you” can be hard; our generations contain the first people who routinely shop religions, for instance. But the sometimes poignant difficulty of finding yourself merely underscores how essential it is. Silver says the costs of germline engineering and a college education might be roughly comparable; in both cases, he goes on, the point is to “increase the chances the child will become wiser in some way, and better able to achieve success and happiness.” But that’s half the story, at best. College is where you go to be exposed to a thousand new influences, ideas that should be able to take you in almost any direction. It’s where you go to get out from under your parents’ thumb, to find out that you actually don’t have to go to law school if you don’t want to. As often as not, the harder parents try and wrench their kids in one direction, the harder those kids eventually fight to determine their own destiny. I am as prepared as I can be for the possibility — the probability — that Sophie will decide she wants to live her life in the concrete heart of Manhattan. It’s her life (and perhaps her kids will have a secret desire to come wander in the woods with me).

We try and shape the lives of our kids — to “improve” their lives, as we would measure improvement — but our gravity is usually weak enough that kids can break out of it if and when they need to. (When it isn’t, when parents manage to bend their children to the point of breaking, we think of them as monstrous.) “Many of the most creative and valuable human lives are the result of particularly diffcult struggles” against expectation and influence, writes the legal scholar Martha Nussbaum.

That’s not how a genetic engineer thinks of his product. He works to ensure absolute success. Last spring an Israeli researcher announced that he had managed to produce a featherless chicken. This constituted an improvement, to his mind, because “it will be cheaper to produce since its lack of feathers means there is no need to pluck it before it hits the shelves.” Also, poultry farmers would no longer have to ventilate their vast barns to keep their birds from overheating. “Feathers are a waste,” the scientist explained. “The chickens are using feed to produce something that has to be dumped, and the farmers have to waste electricity to overcome that fact.” Now, that engineer was not trying to influence his chickens to shed their feathers because they’d be happier and the farmer would be happier and everyone would be happier. He was inserting a gene that created a protein that made good and certain they would not be producing feathers. Just substitute, say, an even temperament for feathers, and you’ll know what the human engineers envision.

“With reprogenetics,” writes Lee Silver, “parents can gain complete control [emphasis mine] over their destiny, with the ability to guide and enhance the characteristics of their children, and their children’s children as well.” Such parents would not be calling their children on the phone at annoyingly frequent intervals to suggest that it’s time to get a real job; instead, just like the chicken guy, they would be inserting genes that produced proteins that would make their child behave in certain ways throughout his life. You cannot rebel against the production of that protein. Perhaps you can still do everything in your power to defeat the wishes of your parents, but that protein will nonetheless be pumped out relentlessly into your system, defining who you are. You won’t grow feathers, no matter how much you want them. And maybe they can engineer your mood enough that your lack of plumage won’t even cross your mind.

Such children will, in effect, be assigned a goal by their programmers: “intelligence,” “even temper,” “athleticism.” (As with chickens, the market will doubtless lean in the direction of effciency. It may be hard to find genes for, say, dreaminess.) Now two possibilities arise. Perhaps the programming doesn’t work very well, and your kid spells poorly, or turns moody, or can’t hit the inside fastball. In the present world, you just tell yourself that that’s who he is. But in the coming world, he’ll be, in essence, a defective product. Do you still accept him unconditionally? Why? If your new Jetta got thirty miles to the gallon instead of the forty it was designed to get, you’d take it back. You’d call it a lemon. If necessary, you’d sue.

Or what if the engineering worked pretty well, but you decided, too late, that you’d picked the wrong package, hadn’t gotten the best features? Would you feel buyer’s remorse if the kid next door had a better ear, a stronger arm?

Say the gene work went a little awry and left you with a kid who had some serious problems; what kind of guilt would that leave you with? Remember, this is not a child created by the random interaction of your genes with those of your partner, this is a child created with specific intent. Does Consumer Reports start rating the various biotech offerings?

What if you had a second child five years after the first, and by that time the upgrades were undeniably improved: how would you feel about the first kid? How would he feel about his new brother, the latest model?

The other outcome — that the genetic engineering works just as you had hoped — seems at least as bad. Now your child is a product. You can take precisely as much pride in her achievements as you take in the achievements of your dishwashing detergent. It was designed to produce streak-free glassware, and she was designed to be sweet-tempered, social, and smart. And what can she take pride in? Her good grades? She may have worked hard, but she’ll always know that she was spec’ed for good grades. Her kindness to others? Well, yes, it’s good to be kind — but perhaps it’s not much of an accomplishment once the various genes with some link to sociability have been catalogued and manipulated. I have no doubt that these qualms would be one of the powerful psychological afflictions of the future — at least until someone figures out a fix that keeps the next generations from having such bad thoughts.

Britain’s chief rabbi, Jonathan Sacks, was asked, a few years ago, about the announcement that Italian doctors were trying to clone humans. “If there is a mystery at the heart of human condition, it is otherness: the otherness of man and woman, parent and child. It is the space we make for otherness that makes love something other than narcissism.” I remember so well the feeling of walking into the maternity ward with Sue, and walking out with Sue and Sophie: where there had been two there were now, somehow, three, each of us our own person, but now commanded to make a family, a place where we all could thrive. She was so mysterious, that Sophie, and in many ways she still is. There are times when, like every parent, I see myself reflected in her, and times when I wonder if she’s even related. She’s ours to nurture and protect, but she is who she is. That’s the mystery and the glory of any child.

Mystery, however, is not one of the words that thrills engineers. They try and deliver solid bridges, unyielding dams, reliable cars. We wouldn’t want it any other way. The only question is if their product line should be expanded to include children.

Right now both the genes, and the limits that they set on us, connect us with every human that came before. Human beings can look at rock art carved into African cliffs and French caves thirty thousand years ago and feel an electric, immediate kinship. We’ve gone from digging sticks to combines, and from drum circles to symphony orchestras (and back again to drum circles), but we still hear in the same range and see in the same spectrum, still produce adrenaline and dopamine in the same ways, still think in many of the same patterns. We are, by and large, the same people, more closely genetically related to one another than we may be to our engineered grandchildren.

These new technologies show us that human meaning dangles by a far thinner thread than we had thought. If germline genetic engineering ever starts, it will accelerate endlessly and unstoppably into the future, as individuals make the calculation that they have no choice but to equip their kids for the world that’s being made. The first child whose genes come in part from some corporate lab, the first child who has been “enhanced” from what came before — that’s the first child who will glance back over his shoulder and see a gap between himself and human history.

These would be mere consumer decisions — but that also means that they would benefit the rich far more than the poor. They would take the gap in power, wealth, and education that currently divides both our society and the world at large, and write that division into our very biology. A sixth of the American population lacks health insurance of any kind — they can’t afford to go to the doctor for a checkup. And much of the rest of the world is far worse off. If we can’t afford the fifty cents a person it would take to buy bed nets to protect most of Africa from malaria, it is unlikely we will extend to anyone but the top tax bracket these latest forms of genetic technology. The injustice is so obvious that even the strongest proponents of genetic engineering make little attempt to deny it. “Anyone who accepts the right of affluent parents to provide their children with an expensive private school education cannot use “unfairness” as a reason for rejecting the use of reprogenetic technologies,” says Lee Silver.

These new technologies, however, are not yet inevitable. Unlike global warming, this genie is not yet out of the bottle. But if germline genetic engineering is going to be stopped, it will have to happen now, before it’s quite begun. It will have to be a political choice, that is — one we make not as parents but as citizens, not as individuals but as a whole, thinking not only about our own offspring but about everyone.

So far the discussion has been confined to a few scientists, a few philosophers, a few ideologues. It needs to spread widely, and quickly, and loudly. The stakes are absurdly high, nothing less than the meaning of being human. And given the seductions that we’ve seen — the intuitively and culturally delicious prospect of a better child — the arguments against must be not only powerful but also deep. They’ll need to resonate on the same intuitive and cultural level. We’ll need to feel in our gut the reasons why, this time, we should tell Prometheus thanks, but no thanks.