We're worrying about genetically engineered babies—again. Earlier this month, the journal Nature published an opinion piece calling for a moratorium on the use of new gene-editing technologies to modify the DNA of human embryos. The authors, led by Edward Lanphier—the CEO of Sangamo Biosciences, a biotechnology company that develops gene-editing technologies—argued that changing the DNA of human embryos or gametes with current methods "could have unpredictable effects on future generations," and is therefore "dangerous and ethically unacceptable."

The letter was prompted by a story also published earlier this month in MIT Technology Review, which described just how easily human embryos could be modified with state-of-the-art DNA editing technologies. The article identified several academic labs and a Boston biotechnology company that are trying to use those methods to correct disease-causing mutations by editing the DNA of human gametes and embryos. It cited anonymous sources claiming that genetically engineered human embryos had already been produced in China, and "that results describing edited [human] embryos were pending publication."

Leon Kass, who was about to head up President Bush's bioethics council, warned that "human nature itself lies on the operating table ... ready for wholesale redesign."

Does this story sound familiar? It should, because we've heard it before. Every decade or so, some new development in biotechnology prompts us to worry that we're about to enter a risky new era of genetically engineered children. Back in 2001, the technology was human cloning, but the storyline was similar: Academic labs were pushing boundaries, both technical and ethical. A Boston biotechnology company was cloning human embryos. Experiments considered outside the realm of professional standards in the United States were already underway in a foreign country with fewer ethical restrictions. There were the inevitable Brave New World references, and calls for a ban on the innovations. Leon Kass, who was about to head up President Bush's bioethics council, warned that "human nature itself lies on the operating table ... ready for wholesale redesign." If we want to maintain our humanity, Kass wrote, "the time has come to pay attention."

We were also supposed to pay attention after the birth of the first child conceived through in vitro fertilization, in 1978. In an interview with one of the developers of the technology, the Canadian Family Physician asked, "Could it mean selection of a 'master race', generating babies solely for their physical and mental characteristics? ... Was the brave new world that Aldous Huxley envisaged so very far away?" And Brave New World itself, published in 1932, was a warning about the dystopian possibilities of a world in which we use biotechnology to engineer the next generation. Aldous Huxley's concern wasn't even prompted by a new technology; rather, it was a response to newly developed theoretical principles in genetics. These principles could be used to design sophisticated breeding programs, a prospect which was enthusiastically anticipated by several human eugenics societies that were active in the early 20th century.

We've been repeatedly warned that biotechnology is on the brink of forcing us to confront the major ethical questions raised by the ability to eugenically design our offspring. Should parents be allowed to use genetic engineering to enhance the IQ or the athletic ability of their children? Should everyone have access to this technology, or will we live in a society where only the rich can genetically enhance their offspring? And is it right to make these kinds of decisions for unborn children, who have no say in the matter?

Have we been too optimistic about the progress of genetic engineering? And how will we know when it's really time to worry about the ethical implications of designer babies?

Yet, in spite of more than a century of concern, these questions have remained almost completely hypothetical. Nobody today, no matter how wealthy, is able to pay a company to genetically engineer the IQ of their children. Have we been too optimistic about the progress of genetic engineering? And how will we know when it's really time to worry about the ethical implications of designer babies?

As it turns out, the warnings about the eugenic potential of biotechnology are spot on. All of the methods that have raised concerns about human eugenics, including sophisticated breeding programs, in vitro fertilization, reproductive cloning, and genetically modified embryos, are now routinely used by scientists to create designer animals, including mice, rats, rabbits, pigs, sheep, cows, and monkeys. There is no reason why the same procedures can't work just as well in humans after a little optimization. The technology to make designer babies is already here.

Though these technologies work, they aren't particularly efficient. This poses a very non-hypothetical ethical issue: safety. Depending on the specific protocol and the type of DNA edit being attempted, the efficiencies of even the best technologies often fall well below 50 percent, leaving most cells or embryos without the desired edit. To overcome this problem, researchers often produce dozens of animals from edited gametes or embryos in order to get one with the correct DNA change. In order to make this process work in humans, a would-be mother of a genetically engineered baby would likely have to undergo multiple rounds of the moderately invasive and not completely risk-free process of egg retrieval.

More serious is the potential for off-target edits, which happen when the imperfect process creates additional mutations elsewhere in the genome. We don’t know what the health effects of these off-target mutations would be, though they could include an increased risk for cancer, developmental disorders, or other genetic diseases. As Lanphier and his colleagues note in their Nature article, “the precise effects of genetic modification to an embryo may be impossible to know until after birth.” These effects would exist not only in the genetically engineered child, but also in subsequent generations that inherit the off-target mutations. DNA editing technology has improved substantially in the last few years, but it will need to improve a lot more before it becomes feasible to routinely and reliably genetically engineer human embryos.

At the moment, it’s extremely unlikely that any lab is really attempting to create a genetically engineered baby. According to MIT Technology Review, the labs working on human applications of this technology are mainly focused on improving its efficiency in human egg and sperm cells. And even the rumored generation of edited human embryos in a Chinese lab is likely to be no more than a demonstration of the technology, with no pregnancies involved.

Someday the technology will be good enough, and scientists have a wide range of opinions on whether it's ethically acceptable to genetically engineer our offspring. When the technology reaches that point, a company or medical practice is likely to start offering reliable genetic engineering services, and we will then be forced to grapple with the ethical questions about designer babies that have so far been limited to science fiction. But even then, the first applications of this technology are likely to be the most ethically justified ones—DNA editing to correct genetic defects that cause terrible diseases like Alzheimer's or hereditary cancer syndromes, rather than enhancing IQ or athletic ability.

For now, however, the more urgent ethical question we need to confront is non-hypothetical: At what point should we consider the technology safe enough to use on humans? Safety is the foremost reason cited by Lanphier and his co-authors in their call to ban DNA editing of human embryos and reproductive cells. Most leading researchers working in this field would agree—for the time being. Before we worry about the most sensational possibilities of designer babies, we need to resolve the more mundane but much more urgent question of how safe it is to make them.

Inside the Lab explores the promise and hype of genetics research and advancements in medicine.

Lead photo: (Photo: kit4na/Flickr)