George Church would be a likely source if anyone had unlocked the secret to creating a genetically modified baby. At his Harvard Medical School lab, researchers are rewriting genetic codes and even working on resurrecting the woolly mammoth. Church describes his lab as a center for pushing the boundaries of biology.
During a visit, Church suggested speaking with Luhan Yang, a postdoctoral researcher from Beijing. Yang played a key role in developing CRISPR-Cas9 and co-founded a biotech company with Church focused on modifying livestock DNA. When asked if CRISPR could be used to edit human genes, she didn’t hesitate – yes, it was possible. Her laptop contained a "Germline Editing Meeting" presentation outlining plans to alter human heredity.
Germline editing allows genetic changes in eggs, sperm, or embryos to be passed down through generations. It could eliminate inherited diseases like cystic fibrosis or introduce resistance to Alzheimer’s and aging. But critics warn of a future where parents select traits like intelligence and appearance, creating "designer babies."
CRISPR, already widely used for precise DNA edits, has transformed medicine by offering hope for treating genetic conditions like sickle cell anemia. However, while standard gene therapy only affects individual patients, germline editing would permanently alter human DNA. That’s why it remains highly controversial. Many countries, particularly in Europe, have banned it outright, and international scientific organizations classify such modifications as a threat to human dignity.
Despite ethical concerns, research continues worldwide. Yang’s proposed experiment aimed to correct the BRCA1 mutation in ovarian tissue from a cancer patient, potentially creating viable, mutation-free embryos. She later left the project, and its status remains unclear. Other U.S., China, and the U.K. teams are actively exploring similar research. Reports suggest CRISPR-modified human embryos have already been created in China, though results are still unpublished.
The ultimate goal is to prove genetic corrections can be safely passed through generations. If successful, future treatments could allow doctors to edit eggs or sperm to eliminate inherited conditions before conception. Some believe CRISPR could even be used on early-stage IVF embryos. If perfected, these methods would revolutionize reproductive medicine.
Merle Berger, co-founder of Boston IVF, calls germline engineering a breakthrough but warns of potential misuse. While eliminating diseases may gain public support, modifying genes for intelligence or physical traits could lead to a backlash. “Everyone would want the perfect child,” he says. “We’ve talked about this for years, but now we finally have the ability.”
Editing human embryos with CRISPR is surprisingly straightforward. Jennifer Doudna, a biologist at UC Berkeley, says any skilled molecular biologist could do it. At MIT, researcher Guoping Feng uses CRISPR on marmoset monkeys to study brain disorders. His team injects CRISPR components into fertilized eggs to modify genes like SHANK3, linked to autism. However, the results are inconsistent. Only a fraction of edited embryos produce live births with the intended changes in monkeys, making human applications impractical. Feng estimates germline engineering is at least a decade away due to risks of unintended genetic alterations.
A more promising approach combines CRISPR with stem cell technology. Church’s team and other scientists are working on turning stem cells into eggs and sperm, a scalable alternative to embryo editing. If successful, researchers could modify stem cells before converting them into reproductive cells, allowing precise gene selection before conception.
In December 2013, OvaScience, a biotech firm focused on fertility treatments, briefed investors on its plans to use gene editing for reproductive health. Harvard scientist David Sinclair, who collaborates with Church, described gene editing as preventing inherited diseases. He suggested that in the future, parents could correct harmful mutations in their child’s DNA before conception. Huntington’s disease, for example, could be eliminated from an embryo by editing egg stem cells.
While OvaScience’s research has gained little public attention, it has partnered with synthetic biology company Intrexon to explore gene editing’s role in preventing hereditary diseases. Northeastern University biologist Jonathan Tilly, a leading expert on egg stem cells, confirms his lab is currently using CRISPR to edit egg stem cells to remove a genetic disorder. However, he acknowledges that ethical concerns remain unresolved. Scientists can determine whether these techniques are possible, but the more significant questions, whether they should be used and for what purpose, extend far beyond science.
If germline engineering becomes routine in medicine, it could reshape human health, longevity, and productivity. However, it also raises ethical and social concerns. Would these enhancements be available only to the wealthy? In the U.S., an IVF cycle costs around $20,000, and adding genetic testing or surrogacy can push the price toward $100,000. Some argue that germline editing isn’t even necessary. Stanford ethicist Hank Greely points out that existing embryo screening can prevent many genetic diseases. For example, a man with Huntington’s could fertilize a dozen eggs, and doctors could select embryos without the faulty gene, a process costing about $4,000.
Others see germline engineering as a slippery slope. Edward Lanphier, CEO of Sangamo Biosciences, a company working on gene-editing therapies for HIV, argues there’s no real medical reason for altering embryos. He warns that technology could lead parents to select desirable traits rather than prevent disease. Critics fear genetic advertising from fertility clinics, experimentation on children, and irreversible changes to the human gene pool. The American Medical Association has opposed germline editing, citing unknown long-term risks, though its stance predates CRISPR’s development.
Some scientists predict that compelling medical uses will emerge. Finding a viable embryo might be difficult for couples with multiple genetic conditions. Gene editing could also address infertility. Some men with azoospermia, a condition preventing sperm production, have missing DNA segments on their Y chromosome. Werner Neuhausser, a doctor at Boston IVF and Harvard’s Stem Cell Institute, believes CRISPR could repair these defects, allowing previously infertile men to have biological children. “It would change medicine forever,” he says.
George Church believes CRISPR’s precision makes it an attractive tool for gene therapy. While his lab focuses on modifying animals, he argues the technology could eventually do more than eliminate disease – it could enhance human traits. He frequently lists natural genetic variants linked to exceptional abilities, such as denser bones, resistance to heart disease, or immunity to Alzheimer’s. CRISPR, he suggests, could one day provide these advantages to everyone. Though he insists that experimental procedures should be limited to consenting adults, he acknowledges that earlier intervention is more effective. “The ultimate prevention,” he told an MIT audience, “is correcting genes before birth.” He compared genetic modifications to cosmetic surgery, implying that widespread adoption could become routine.
Some ethicists argue that genetic enhancement is not just acceptable but necessary. John Harris, a bioethicist at the University of Manchester, believes improving the human genome is an ethical responsibility. Public opinion is mixed – according to a 2023 Pew Research survey, 46% of Americans support genetic modifications to prevent disease, while 83% oppose editing embryos to increase intelligence. Yet some thinkers, like Oxford philosopher Nick Bostrom, believe cognitive enhancement could be one of humanity's most critical long-term issues. He argues that even a few genetically enhanced individuals could drive breakthroughs that benefit everyone.
Many experts believe germline engineering is inevitable. Before the first genetically edited child is born, extensive testing on animals will be needed to ensure safety. However, history suggests that society will leap if the risks seem manageable. Neuhausser compares the debate to the early days of IVF when no one knew if the first test-tube babies would live everyday lives. “Someone had to take the plunge,” he says.
In January, 20 scientists, ethicists, and legal experts gathered in Napa Valley to discuss the future of germline editing. The meeting, organized by Jennifer Doudna, a Berkeley scientist who co-discovered CRISPR, aimed to address growing concerns about the technology’s potential use in altering human heredity. Doudna wanted to know if researchers could or should halt its progression.
She emphasized the power of CRISPR, describing it as both groundbreaking and risky. The ability to edit the human germline was no longer hypothetical; it was within reach. Among those at the meeting was Paul Berg, a Nobel Prize-winning biochemist who played a key role in organizing the 1975 Asilomar Conference, where scientists set guidelines for handling recombinant DNA. Doudna hoped a similar agreement could be reached on germline engineering, but enforcing any moratorium would be difficult with research now spanning the globe. Still, she believed if U.S. scientists voluntarily paused such experiments, it might influence researchers elsewhere.
Doudna argued that self-imposed restrictions should prohibit gene-edited babies and work on human embryos, eggs, or sperm. She insisted that safety, efficacy, and ethical considerations needed more study and that nonhuman models could provide critical insights before moving toward human applications. A cautious approach, she said, was necessary.
Not everyone at the meeting agreed on the need for restrictions. Stanford ethicist Hank Greely pointed out that U.S. regulations already prevent germline modifications from being used in reproductive medicine. While he opposed a complete moratorium, he supported a discussion on the issue and eventually signed a statement alongside Doudna and other attendees. Their joint editorial, later published in Science, called for a global pause on clinical applications of germline editing until scientists could determine whether any use would ever be considered acceptable. Though he hadn’t attended the Napa meeting, George Church added his name to the statement.
As public awareness of germline editing grows, biotechnology companies developing CRISPR-based treatments have been forced to clarify their positions. Nessan Bermingham, CEO of Intellia Therapeutics, a Boston-based startup working on gene therapy for children and adults, stated that germline modifications were not part of his company’s agenda. He even suggested that patent control could be used to prevent commercial use of germline editing, emphasizing that the technology was still in its early stages and nowhere near ready for such applications.
The rapid development of CRISPR has made genetic modifications of human embryos a pressing reality. Doudna, reflecting on the implications, questioned whether humanity should exercise such control over its evolution. While she acknowledged the moral and ethical complexities, she also stressed the need for scientists to communicate better what lies ahead. Most people, she warned, have no idea how close this technology is to reshaping the future.
Mary Watson
