The Technology That’s Changing the Future of Human Reproduction

Author Hank Greely on how humans will conceive and reproduce in the brave new world ahead of us.

The following is an excerpt from The End of Sex and the Future of Human Reproduction by Henry T. Greely.

This is a book about the future of our species, about the likely development of revolutionary biological technologies, and about the deep ethical and legal challenges our societies will face as a result. But the best way to sum it up, I think, is to say that it is about the coming obsolescence of sex.

It is not about the disappearance of all the things we mean by the word “sex.” Humans will still (usually) appear at birth having physical attributes of one sex or the other and will be loudly pronounced as either baby girls or baby boys, with the appropriately colored, and gendered, accessories. Our descendants will still (almost all the time) have genetic contributions from both an egg and a sperm, thereby achieving the mixing of parental genes that is also sex or, at least, sexual reproduction. And, I am confident, people will continue to practice sexual intercourse in myriad different ways and for almost all of the current varying, complicated (and uncomplicated) reasons. Except one.

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I expect that, sometime in the next twenty to forty years, among humans with good health coverage, sex, in one sense, will largely disappear, or at least decrease markedly. Most of those people will no longer use sexual intercourse to conceive their children. Instead of being conceived in a bed, in the backseat of a car, or under a “Keep off the Grass” sign, children will be conceived in clinics. Eggs and sperm will be united through in vitro fertilization (IVF). The DNA of the resulting embryos will then be sequenced and carefully analyzed before decisions are made (passive voice intentional) about which embryo or embryos to transfer to a womb for possible development into one or more living, breathing babies.

Prospective parents will be told as much as they want to know about the DNA of, say, 100 embryos and the implications of that DNA for the diseases, looks, behaviors, and other traits of the child each of those embryos might become. Then they will be asked to pick one or two to be transferred into a womb for possible gestation and birth. And it will all be safe, legal, and, to the prospective parents, free.

In short, we humans will begin, very broadly, to select consciously and knowingly the genetic variations and thus at least some of the traits and characteristics of our children. This idea is not new. It has been a subject of hundreds, probably thousands, of stories and novels—Brave New World by Aldous Huxley being, if not the first, certainly the first truly memorable example. It has been the subject of other forms of fiction, notably the 1997 movie Gattaca. And it has been the subject of tens of thousands of books, articles, sermons, and other nonfiction analyses—usually viewed with alarm, but occasionally with (prospective) pride.

This book is different. Not, at its heart, a discussion of the consequences of such a world (although Part III does try to analyze them to some extent), it is a description of precisely how and why that world is going to arrive. Two insights drive the book. The first is the way new techniques, drawn from several different areas of modern bioscience research, will combine to make this future not just possible but cheap and easy. The second is the way economic, social, legal, and political forces will combine to make this future not just achievable but, as I believe, inevitable, in the United States and in at least some other countries. Those insights turn these questions from interesting, goosebump-inducing speculation to real problems that will confront real people—ourselves, our children, and our grandchildren—in the next few decades.

The technical innovations will come from two worlds: genetics and stem cell research. We can already do preimplantation genetic diagnosis (PGD) on embryos. We can take away a few cells from an early “test tube” embryo, test them for a genetic trait or two, and use that information to decide whether to give the embryo a chance to become a baby. PGD sounds like science fiction to many people but it has been used for over a quarter century—the first child born after PGD is now over twenty-five years old. And every year now, around the world, thousands of new children are born after being subjected to PGD as embryos.

But today PGD is only weakly informative, as well as expensive, unpleasant, and even dangerous, thanks both to the limitations of genetic testing and to the necessity of using IVF as part of PGD. These constraints will change. Genetics will allow us to do cheap, accurate, and fast sequencing of the entire 6.4 billion base pair genome of an embryo and will give us an increasingly deep understanding of what that sequence means for disease risks, physical characteristics, behaviors, and other traits of the child that embryo would become. And stem cell research will allow couples to avoid the expensive and (for the women involved) unpleasant and physically risky process of maturing and retrieving human eggs by allowing us to make eggs (and sperm) from stem cells. The result will be a cheap, effective, and painless process I call “Easy PGD.”

Of course, just because technological innovations are possible does not mean they will be adopted. The supersonic commercial jetliner came and went; the flying car and the rocket backpack were never really launched, though both are technically feasible. But unlike those technologies, Easy PGD has a clear path to acceptance in the United States and likely paths to adoption in many other countries. It may not be approved everywhere, but in an increasingly global world, that could well be irrelevant.

The End of Sex and the Future of Human Reproduction


The ideas in the last few paragraphs are the core of this book. I will also discuss some of the potential consequences that widespread adoption of DNA-based embryo selection using Easy PGD will have for individuals, for families, for societies, and for humanity. The fields of genetic selection have been frequently plowed before; I hope the specificity of Easy PGD as the method of choice for parents to select their children’s traits, as well as the near immediacy of the questions it raises, will add some value to my analysis over those that have come before.

Concretely, the book is divided into three parts. Part I provides background information on the science and technology involved in Easy PGD. It gives a nonscientist a guide to the varied ways living things reproduce; to the specifics of how humans reproduce, naturally and by IVF; to DNA, genes, chromosomes, and genetic testing; and to stem cell research. Much of it will be helpful in understanding what follows; I must confess that some of it is here in the hope that you will come to share the excitement and fascination of biology with me, a person whose last biology class was in tenth grade. Part II explains how and why Easy PGD will happen, looking first at the technical developments in genetics (or genomics) and in stem cell science and then at the medical, economic, legal, and political factors that will make it not just acceptable, but widely adopted. Part III examines the broader implications of Easy PGD. It looks at issues of safety, family, equality, coercion, and nature, along with some other more practical consequences of the technology.

I’ve gotten lots of good advice in writing this book, but I haven’t taken all of it. Although IVF, the fountainhead of modern assisted reproductive technologies, is less than forty years old, it has already spawned a vast literature on a wide range of issues, including many fascinating and important matters for which Easy PGD would be relevant, such as surrogacy, parental status, gamete donor rights (and duties), and the positions and roles of religious beliefs, among others. This book could and perhaps should be longer; however, practical considerations mean that the likely interactions between Easy PGD and other issues I do not analyze must await future treatments.

More fundamentally, some people have told me to make an argument—to take a position and fight for it, guns blazing. But I’m a law professor, trained as a lawyer. Lawyers do many things. Sometimes they argue zealously in court for their clients’ positions, whether they believe them or not. But sometimes they lay out all the facts and implications, as they see them, to help clients make their own decisions. I have some views about ways we might want to regulate Easy PGD, but they are tentative, based on glimpses and guesses of the future and on my own preferences and principles. I will share them, but I do not insist on them. But I will ask you to develop opinions. Easy PGD will give prospective parents—including perhaps some who are reading these words—more choices but it will also set some hard questions for all of us. My goals are, first, to get you interested in those questions—as parents, as grandparents, as citizens, as humans—and second, to give you information to help you come to your own conclusions.

Aldous Huxley’s famous novel takes its title from one of Shakespeare’s last plays, The Tempest. Years before the play starts, plotters abandon Prospero, who is both the Duke of Milan and a magician, at sea with his infant daughter, Miranda. They survive on an island with only non-human company. The years go by—Miranda grows up, and fate, working through Shakespeare, delivers the plotters to the island and into Prospero’s hands. Miranda sees them, almost the very first humans she ever remembers seeing, and, not knowing that some of them had long ago plotted her death along with her father’s, she famously exclaims:

O, wonder!
How many goodly creatures are there here!
How beauteous mankind is! O brave new world,
That has such people in’t!

That is often remembered. What few recall (though I am sure Huxley did) was Prospero’s immediate reply: “’Tis new to thee.” My hope is that when Easy PGD opens the prospects of some kind of brave new world, you will be more knowledgeable, and more sophisticated, than Miranda. (And that things will work out as well for you as, happily, they do for her in the end.)


Excerpted from The End of Sex and the Future of Human Reproduction by Henry T. Greely, published by Harvard University Press. Copyright © 2016 by the President and Fellows of Harvard College. Used by permission. All rights reserved.

Meet the Writer

About Henry ‘Hank’ Greely

Hank Greely is a professor of law who teaches law and genetics at Stanford University in Stanford, California. He’s the author of The End of Sex and the Future of Human Reproduction (Harvard University Press, 2016).

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