George Church towers over most people. He has the long, gray beard of a wizard from Middle-earth, and his life’s work—poking and prodding DNA and delving into the secrets of life—isn’t all that far removed from a world where deep magic is real. The 63-year-old geneticist presides over one of the largest and best-funded academic biology labs in the world, headquartered on the second floor of the massive glass and steel New Research Building at Harvard Medical School. He also lends his name as an adviser or supporter to dozens of projects, consortiums, conferences, spinouts, and startups that share a mission to push the outer edge of everything, from biorobotics to bringing back the woolly mammoth. And on a steamy August morning last summer, he wants to talk to me about the outer edge of my life.

Church is one of the leaders of an initiative called the Genome Project-­Write, or GP-Write, which is organizing the efforts of hundreds of scientists around the world who are working to synthesize the DNA of a variety of organisms. The group is still debating how far to go in synthesizing human DNA, but Church—standing in his office in a rumpled sport coat, behind the slender lectern he uses as a desk—says his lab has already made its own decision on the matter: “We want to synthesize modified versions of all the genes in the human genome in the next few years.”

His plan is to design and build long chains of human DNA, not solely by cutting and pasting small fixes—a now-routine practice, thanks to recent technologies like Crispr that let scientists edit DNA cheaply and easily—but by rewriting critical stretches of chromosomes that can then be stitched together with a naturally occurring genome. If they succeed, it will be a breathtaking leap in ambition and complexity from the genomes of bacteria and yeast that scientists up until now have worked to synthesize. “What we’re planning to do is far beyond Crispr,” Church says. “It’s the difference between editing a book and writing one.”

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April 2018. Subscribe to WIRED. Nik Mirus

In writing the book, Church hopes to bend the human narrative to his will. By replacing select nucleo­tides—the ACGTs of life, which are scattered throughout the chromosomes—and changing, say, a T to an A or a C to a G in a process called recoding, Church envisions being able to make cells resistant to viruses. “Like HIV and hepatitis B,” he says.

“And the common cold?” I ask.

He nods yes, adding that they’ve already recoded bacteria to be virus-resistant. “It’s in a paper we published in 2016,” he says.

Church and others who are working to synthesize human DNA have created their own effort within GP-Write—the Human Genome Project-Write, or HGP-Write—and its prospects for success have biologists abuzz over the potential for treating diseases and for creating bioengineered cells and possibly even organs. Critics, though, are scratching their heads over the technical challenges, high costs, and practicality. Francis Collins, director of the National Institutes of Health, acknowledges that synthesizing a full human genome is feasible, but he doesn’t quite see the point. “I think it’s probably within the range of possibility, given enough time and money,” he says, “but why would you want to do that? Technologies like Crispr are so much more accessible right now.”

There are also the ethics of using a powerful new technology to muck around with life’s basic coding. Theoretically, scientists could one day manufacture genomes, human or otherwise, almost as easily as writing code on a computer, transforming digital DNA on someone’s laptop into living cells of, say, Homo sapiens. Mindful of the controversy, Church and his HGP-Write colleagues insist that minting people is not their goal, though the sheer audacity of making genome-scale changes to human DNA is enough to cause controversy. “People get upset if you put a gene from another species into something you eat,” says Stanford bioethicist and legal scholar Henry Greely. “Now we’re talking about a thorough rewriting of life? Hairs will stand on end. Hackles will be raised.”