Three years ago, when CRISPR-Cas9, a method of precisely editing DNA, suddenly appeared liked a technology from the future, scientists realized we could now engineer the human race by giving our children and their heirs improved genes. But many disavowed that we would do so soon.

The biologist Weizhi Ji, who created two gene-edited macaque monkeys at Kunming Biomedical International, said that creating humans with CRISPR-edited genomes was “very possible,” but added that “considering the safety issue, there would still be a long way to go.” (See “10 Breakthrough Technologies: Genome Editing.”)

Yet I was sure that scientists would research how to edit the human germ line, and quickly. (“Germ line” is biologists’ jargon for the egg and the sperm, which combine to form an embryo. Editing the DNA of such cells, or of the embryo itself, would pass heritable changes to future generations.)

They would try because editing genes with CRISPR was trivially easy, and it would be a sensational thing to do. “Any scientist with molecular biology skills and knowledge of how to work with [embryos] is going to be able to do this,” says Jennifer Doudna, a biologist at the University of California, Berkeley, who in 2012 co-discovered how to use CRISPR to edit genes.

Mostly, they would research CRISPR because it seems a powerful way to prevent disease from birth. Guoping Feng, a neurobiologist at MIT’s McGovern Institute for Brain Research, believes that gene-edited human beings are “10 to 20 years away,” but nonetheless approves of human germ-line editing. Feng says, “To me, it’s possible in the long run to dramatically improve health, lower costs. It’s a kind of prevention.”

Why not use CRISPR to eliminate diseases like Huntington’s, a terrible, fatal neurodegenerative disorder triggered by a defect in a single gene? Or why not correct the DNA of an embryo with a mutation in a gene called BRCA1, which causes ovarian and breast cancer? While you’re fiddling with an embryo’s DNA, why not insert naturally occurring gene variants that confer extraordinary characteristics like unbreakable bones or resistance to diseases like Alzheimer’s?

As our biomedicine editor, Antonio Regalado, reports in this issue’s cover story, “Engineering the Perfect Baby,” experiments designed to correct the DNA in a woman’s egg or a man’s sperm, or to directly edit the DNA of an early-stage embryo using CRISPR, are already being carried out.

Why not? One concern is that the technologies would not be widely available, at least at first. Their expense would mean only rich people would have perfect children. Another worry is that germ-line engineering would affect unborn people without their consent. The most potent objection is that we don’t know what we’re doing: if you provide immunity to a disease, you might break something in a genome.

History insists that when a technology has obvious utility, it will be used. But how we use a new technology is our choice. In March, writing in the journal Science, a group of scientists including Doudna and two Nobel laureates called for a great debate on the genetic engineering of humans and a moratorium on any effort to create engineered babies. Crucially, the scientists did not ask their peers to stop using CRISPR to edit human embryos for research purposes; but they recommended convening a “globally representative” group of government agencies, ethics experts, and scientists to suggest policies to guide that research.

Let’s have that debate. Write to me at jason.pontin@technologyreview.com.