CRISPR genetic modification should not be used on humans.

We Need a Moratorium on Genetically Modifying Humans

We Need a Moratorium on Genetically Modifying Humans

The state of the universe.
Nov. 30 2015 12:16 PM

We Need a Moratorium on Genetically Modifying Humans

The technology for potentially creating designer babies has progressed much faster than the deliberation.

designer babies.
Genetically modifying humans could have real and powerful benefits such as preventing genetic diseases, but today it is risky and unpredictable.

Photo illustration by Juliana Jiménez. Photo by Thinkstock.

What if I could make a designer baby for you?

People have alternately worried about and scoffed at that question for decades. The debate has been around for as long as scientists have had the know-how to genetically modify organisms. But just in the last three years, the next generation of GMO technology has emerged.


And it is awesome.

The new technology makes it much more feasible to try to create designer babies. Should we take the plunge? Where did this technology come from so suddenly? And how should we use it responsibly?

This new genetic modification technology is called CRISPR, short for clustered regularly interspaced short palindromic repeats. It is fast, powerful, and cheap. For these reasons it is already ubiquitous in thousands of research labs all over the world. Some researchers are using CRISPR to make genetically modified plants and animals. GMOs that might have taken years and millions of dollars to produce in the past can now be created with CRISPR in weeks or a few months for just thousands of dollars.

The CRISPR system has a combination of tools that allow it to locate specific genomic addresses, snip DNA with a molecular scissors right there, and then rewrite the genetic code at the site of the cut. CRISPR was discovered in certain bacteria that naturally use the system to defend themselves against viral infections by slicing up the virus’ DNA. Scientists figured out that CRISPR could be used pretty much in any cell type—including human—to make very precise genetic modifications. The use of CRISPR is most often referred to as “gene editing” by scientists, but that is synonymous with genetic modification.


Those of us doing genetic research are thrilled at this new tool. For instance, in my lab we conduct research on stem cells and cancer in part now using CRISPR. We have genetically modified specific genes in human cancer cells. Our goal with this CRIPSR-based research is to determine the genetic mechanisms by which tumors begin.

Despite all our excitement in the scientific community, there is a Dr. Jekyll and Mr. Hyde kind of catch here. CRISPR could be used to attempt to make genetically modified humans babies. The technique could alter the genetic code in a human egg cell, human sperm, or a one-cell embryo made from sperm and egg by in vitro fertilization. Recent research using CRISPR to produce genetically modified animals suggests that the same system could in principle successfully create human designer babies.

I call these hypothetical genetically modified human beings GMO sapiens as a mashup of GMO and Homo sapiens, and I discuss the implications of such creatures in my new book, GMO Sapiens: The Life-Changing Science of Designer Babies. In principle it may be fairly straightforward to try to make GMO sapiens using CRISPR. Would it be safe and effective or disastrous? Would it be ethical? Legal?

CRISPR and other similar new genetic modification technologies are so new that discussions of these tough questions have only just started, and we do not have a lot of time to chart a path. Human genetic modification is on the table. Already a different, non-CRISPR kind of experimental human genetic modification is now permitted to proceed in the U.K. based on a legal change earlier this year. This procedure, using cloninglike technology to combine one woman’s egg nucleus with a donor’s egg cytoplasm to create a new hybrid egg, aims to achieve the noble goal of preventing a rare kind of genetic disease. However, there are risks, and the children produced would be genetically modified. At least one U.K. researcher also just requested permission to use CRISPR to make genetically modified human embryos.


In China just a few months ago, researchers said they already did just that and sparked a firestorm in the science community. Strangely, the public has been relatively unaware of this development and the ensuing debate. The researchers made genetically modified human embryos as a research exercise and let them develop for only a few days in the lab. But if someone else followed suit and simply implanted the CRISPR’d human embryos into a surrogate, then boom—we may have the first GMO sapiens.

An additional cautionary note comes from the fact that the researchers making the first GMO sapiens embryos found that the technique didn’t work so well. Sometimes CRISPR made the genetic modifications in the wrong place in the embryo genome. At other times, only certain cells were modified and not others; as the human embryos grew, they would have developed a dangerous condition referred to as mosaicism.

Even with rapidly evolving improvements in CRISPR technology, there would be huge risks to both individuals and society if we go down this path. Instead of making “better” humans (whatever that means), genetic modification could make people who are even sicker or cause them to die. There are some influential advocates for rapidly moving forward with human genetic modification, including Harvard linguist Steven Pinker, but we would be very wrong to rush. Pinker also recklessly said that bioethicists should “get out of the way” of the use of CRISPR on people.

Starting on Dec. 1 in Washington, D.C., the U.S. National Academy of Sciences will hold an international summit on human gene editing with its Chinese and British counterparts. I will be there blogging the meeting at to give the wider community, including the public, a window into what is discussed there.

Admittedly, the idea of making genetic modifications in people is seductive, and it could have real and powerful benefits such as preventing genetic diseases, but today it is risky and unpredictable. There is also no particular boundary to someone running with this technology in other directions, such as attempts at designer babies. We are talking about heritable changes in the human genome that could be passed on potentially forever—we know of no proven safe way to reverse genetic modifications in people. Finally, there has been far too little time for democratic discourse involving the public in the broader question of whether we should hack the human code in this way. I strongly favor a moratorium on clinical use of CRISPR in humans, and I hope that the National Academy of Sciences meeting this week comes to that consensus.

Ask Paul Knoepfler questions about this topic or about his book on Reddit, where he’ll be doing an “ask me anything” discussion on Dec. 7 at 10 a.m.