In 2018 news broke that a Chinese scientist, He Jiankui, had used CRISPR to edit human embryos, and twin girls had been born as a result. The story set off an explosive bioethical controversy. As gene editing expert Kiran Musunuru put it, “He Jiankui’s genetic misadventures were the biggest medical story of the century so far.” Scientists and the public had a lot of questions. What was the unmet medical need that justified the gene editing? Was the science ready for prime time? And, if it was, was He Jiankui the right scientist to do it? Seven years later these questions are far from resolved.
Credits
Host: Alexis Pedrick
Executive Producer: Mariel Carr
Producer: Rigoberto Hernandez
Associate Producer: Sarah Kaplan
Audio Engineer: Samia Bouzid
Music by Blue Dot Sessions
Resource List
Baylis, Françoise. Altered Inheritance: CRISPR and the Ethics of Human Genome Editing. Cambridge, MA: Harvard University Press, 2019.
CBS News. “Chinese Researcher Claims He Helped Make First Gene-Edited Babies.” CBS News, November 26, 2018.
CBS News. “Chinese Scientist Behind Gene-Edited Babies Sentenced to 3 Years in Prison.” CBS News, December 30, 2019.
Cobb, Matthew. As Gods: A Moral History of the Genetic Age. New York: Basic Books, 2022.
Greely, Henry T. CRISPR People: The Science and Ethics of Editing Humans. Cambridge, MA: MIT Press, 2021.
“He Jiankui presentation and Q&A, International Summit on Human Genome Editing.” Youtube Video, November 26, 2018.
Marchione, Marilynn. Associated Press. “Chinese researcher claims first gene-edited babies.” AP News, November 26, 2018.
“Meet Cathy Tie, Bride of ‘China’s Frankenstein.’” MIT Technology Review, May 23, 2025.
Musunuru, Kiran. The CRISPR Generation: The Story of the World’s First Gene-Edited Babies. BookBaby, 2019.
NBC News. “Chinese Scientist Says He Helped Create First Gene-Edited Babies.” NBC News, November 26, 2018.
“World’s first successful tailor-made gene therapy saves baby born with rare disorder.” CBS Mornings. May 16, 2025.
Transcript
Alexis Pedrick: From the Science History Institute, I’m Alexis Pedrick, and this is Distillations. All season we’ve been talking about the hopes but also the fears of genetic engineering.
Alfred Vellucci – NOVA The Gene Engineers: They don’t even know what’s going to eventually come out of this experimentation. It could be anything. It could be contamination, infections, something that could crawl out of the laboratory, such as a Frankenstein.
Jonathan King – Cambridge Hearings: I am convinced that when the people of the community understand the unbelievably unknown nature of the dangers tampering with millions of years of evolution, they’ll say, “No.”
Alexis Pedrick: From the beginning, people have been anxious about the unintended consequences of genetic engineering, but they’ve also been worried about people using it in intentionally harmful ways.
This is a public comment from a recombinant DNA summit in 1977.
Ted Howard – Co-Director of the People’s Business Commission: Well, one thing about technology and science today is whatever can be done is usually going to be done. And just because some scientists say that they don’t want to create a new race of Superman as Adolf Hitler did, doesn’t mean that it’s not going to happen.
Alexis Pedrick: At the time, many people dismissed this comment. The concern was so hypothetical. The science itself was still so far off. Why bother talking about it? But there was reason to worry.
This is Matthew Cobb, the author of As Gods: A Moral History of the Genetic Age.
Matthew Cobb: I mean, people immediately become interested in seeing, “Is there any limit to the kind of cell that we can manipulate?” And the biomedical community starts to think about, “Well, can we use this to change human genes?”
Alexis Pedrick: Three decades after that public comment, something new was about to enter the genetic engineering toolbox, and it would bring us a lot closer to those 1977 eugenics fears.
Matthew Cobb: I remember reading the article when it came out in 2008, in Science, and I went, “Okay, bacteria have an immune system. That’s weird.” And then turned the page. And this is why I am neither a millionaire nor a Nobel Prize winner, because lots of clever people thought, “Aha! Wait a minute.”
Alexis Pedrick: This discovery led to arguably the biggest breakthrough in genetic engineering yet: CRISPR. When it was announced to the world in 2012, it caused a huge frenzy and brought a lot of attention to its creator: a biochemist and professor at UC Berkeley.
NBC News, June 27, 2017: Her name is Jennifer Doudna. And in academic circles, she’s become a kind of rockstar as co-creator of a scientific storm that’s sweeping the whole world.
Jennifer Doudna Archive: I describe it as a surgery for the cell.
Alexis Pedrick: CRISPR stands for “clustered regularly interspaced short palindromic repeats.” It’s a gene editing tool commonly described as “genetic scissors” because, in very simple terms, it can edit a DNA sequence with the same kind of ease and precision as editing a manuscript with a word processor.
Jennifer Doudna Archive: You know, it’s sort of making precise changes to the code of life, you know? It means that we can control human evolution. Now, we can control essentially anything that is alive. We can manipulate the script.
Alexis Pedrick: The implications were enormous. And Doudna and her colleagues were thrilled at the possibilities. CRISPR would have the potential to fix or replace missing genes and cure genetic diseases. But scarier possibilities begin to enter Jennifer Doudna’s subconscious.
This is Hank Greely, a law professor and director of the Stanford Center for Law and the Biosciences.
Hank Greely: She had a dream in which a friend of hers brought a man to see her and asked her to explain CRISPR to this man. She thought the man was a little odd because he always kept his back toward her, but he was nodding. It seemed like he was understanding. And so she finished talking about CRISPR.
He said it was very interesting, turned around; and he was Adolf Hitler. Although in her dream he had a pig’s nose–he had a pig snout–but he was Hitler with a pig snout. And she said she woke up in a cold sweat and decided that she really needed to pay more attention to these issues.
Alexis Pedrick: The dream was very prescient. In 2018, this story broke.
CBS News November 26, 2018: The Chinese researcher has created an international controversy over science and ethics after claiming he helped make the world’s first genetically edited babies.
CBS News November 26, 2018: Twin girls whose DNA he says he altered with a powerful new tool that lets scientists edit the genetic code.
Alexis Pedrick: The scientist’s name was He Jiankui. Some people call him “JK”, and he was beaming when he made the announcement on YouTube.
He Jiankui, NBC News: Two beautiful little Chinese girl named “Lulu” and “Nana” came crying into the world as healthy as any other babies.
Matthew Cobb: He Jiankui had gone ahead and done this, and he thought he was going to win the Nobel Prize, and that everybody was going to applaud him and say how marvelous it was.
Alexis Pedrick: But this is not what happened at all.
Robert Klitzman, NBC Nightly News: There has been consensus that to take an embryo with altered genes and put it in a woman to create a child is just beyond the pale in terms of what’s morally acceptable.
NBC Nightly News, Nov. 26, 2018: And that’s what he says he’s done.
Robert Klitzman, NBC Nightly News: That was exactly what he has said he’s done.
Alexis Pedrick: By the time Lulu and Nana were born in 2018, concerns about genetically modifying human beings had been swirling around for decades. So what went wrong? Was there a clear line in the sand that He Jiankui crossed? And if so, why didn’t anyone stop him from crossing it?
As usual, the story is complicated, and it raises more questions than answers. Including this one: whose responsibility is it to make sure scientists act ethically? But before we can answer these questions, we need to go back to the beginning, before CRISPR was even in the toolbox.
Chapter One. CRISPR Changed Everything.
Alexis Pedrick: Starting in the 1980s, scientists began to work out how to precisely edit DNA.
Matthew Cobb: So in principle, the idea very quickly came up. “Okay, well, we could actually change one of those letters, make it right, and now, hey presto, somebody’s been cured.” So, these ideas started to float about very quickly. And the initial method of doing this was using some enzymes rather exotically called “zinc finger enzymes,” which have zinc in them. And I guess they look like fingers.
Alexis Pedrick: These enzymes would bind with a targeted sequence of DNA, and then other enzymes would slice the DNA.
Matthew Cobb: Cells don’t like having their DNA chopped up. It’s not good for them. And they will try and fix it.
Alexis Pedrick: This is Kiran Musunuru, a cardiologist, expert in gene editing, and author of the CRISPR Generation.
Kiran Musunuru: And as it tries to repair the DNA, it makes mistakes. And so you’re wondering, “Well, how is that a good thing?” Well, if you’re trying to make a change, this is actually a good way to do it. So, you can take advantage of the fact that cells trying to repair it, exploit that. And if you contrive things just right, you can actually get it to make the change that you want.
Alexis Pedrick: But it wasn’t perfect.
Kiran Musunuru: The tool worked, but it didn’t work very well at all, and it was very challenging to use.
Alexis Pedrick: In 2009, Musunuru switched from working with zinc fingers to something called “TALENs.”
Kiran Musunuru: They have a great name because they sound like things you can actually use to cut.
Alexis Pedrick: TALENs worked well if you wanted to turn off a gene.
Kiran Musunuru: It’s very easy to break things like, you know, take a laptop computer. I can come up with many, many ways to break it, right? I can drop it on the floor. I can throw it against a wall. I can pour orange juice on it. Right? And so the original gene editing tools were a lot like that. They were crude but effective.
Alexis Pedrick: But you don’t always want to break things. Sometimes you want to fix things. And that’s where CRISPR comes in. CRISPR enabled cutting and pasting DNA with precision.
Kiran Musunuru: What we saw is that the least efficient, the least effective CRISPR targeting, in terms of making a change at a desired location in the genome, was way better than the best, most effective example we had of TALENs going after any one of these locations. It wasn’t even close. It was immediately clear that, “Wow, we’re in a whole new world.” Gene editing is just taking a huge leap forward.
Matthew Cobb: CRISPR absolutely changed everything.
Alexis Pedrick: This is a clip from an interview with Jennifer Doudna.
Archive: Jennifer Doudna Interview: This is going to revolutionize human life. It’s already beginning. It’s going to mean that all of the genetic defects that have caused so much pain and suffering for people for millions of years, all of that could potentially be removed. So why does the great woman who invented this wake up in the middle of the night worrying about it?
Jennifer Doudna Archive: Interview with Jennifer Doudna: When I started this research project, we were certainly not thinking about technology that would allow alteration of human evolution or anything of that nature. And over the last few years, I’ve gone from wide-eyed excitement to realizing that there was real risk and that we really needed to be aware of this and discussing it. And one of the things that sort of brought that to the forefront of my mind was a dream that I had.
Alexis Pedrick: It was the dream about Hitler with the pig snout.
Jennifer Doudna Archive: Interview with Jennifer Doudna: You know, it sounds funny in a way, to relate that image. But in the dream, it was a terrifying thing. And I really felt real, just, you know, stone cold fear in the dream. And that was really one of the things that motivated me to, you know, to get out of the lab and start talking to people more broadly about the technology, about its capabilities, about the great things about it, but also about things that really required really deep thought and careful consideration and regulation.
Alexis Pedrick: CRISPR is really accessible, and this is one of the things that makes it so scary. In theory, anyone can edit genes. So, it begs the obvious question: will they all use CRISPR for good? And who defines what good is, anyway?
Plagued by questions like these, Jennifer Doudna assembled a small group of advisors and colleagues in Napa, California, in January of 2015. The group was just 18 people, and it included Hank Greely, the Stanford law professor we heard from earlier.
There were also two Nobel laureates there: Paul Berg and David Baltimore. If you’ve listened to the rest of this season, their names will sound familiar. In the 1970s, they called for a moratorium on their own work in recombinant DNA because they were worried about its potential dangers. They then organized the 1975 Asilomar Conference to figure out how to move the work forward safely.
The Napa meeting only lasted a day, but everyone left with a homework assignment to help draft a document with recommendations on how to proceed. This is Hank Greely.
Hank Greely: So our consensus, which really emerged quickly during the meeting and ultimately became an article published in Science a little later that year. It was not detailed. It was not intended to be specific guidelines, let alone regulations or legislation.
Alexis Pedrick: The document had some common sense recommendations: create forums in which experts in bioethics can provide information and education. Encourage and support transparent research. Hank Greely says the group was motivated to work quickly because of a rumor that was going around.
Hank Greely: That somebody in China was about to publish something. I don’t know who knew that. I don’t know how early they knew that, but certainly the fact that people were moving forward, I think, added impetus for some people to really get this statement out.
Alexis Pedrick: Maybe it was fate. Maybe it was just a really good read of the room. Either way, it was the right move because that rumor was about to be proven true.
Chapter Two. The First Line in the Sand is Crossed.
Alexis Pedrick: Just a month later, there was an announcement that made it clear that genetically modifying human embryos was not just a possibility; it was already happening.
This is Francoise Baylis, a bioethicist and author of the book Altered Inheritance.
Francoise Baylis: So in 2015, we had for the first time, a scientist willing to publish an article in which he reported having made genetic modifications to human embryos. Up until this point, either people were doing it and hadn’t reported it, or they weren’t doing it, at least not in a human.
Alexis Pedrick: The scientist Junjiu Huang was from China. Now, just to be clear, this is not He Jiankui who we talked about earlier. He won’t come into this story until a few years later, in 2018. Junjiu Huang used CRISPR to modify human embryos, but he didn’t implant them into a uterus like He Jiankui would go on to do. The embryos he modified were non-viable. Still, this was alarming. No one had taken this step yet, and it was ethically controversial.
Francoise Baylis: Why? Because for the first time, this work which had been done in non-human animals, was being done in a human.
Alexis Pedrick: Both Nature and Science rejected the article on ethical grounds, and it was published in a less prestigious journal: Protein and Cell. A big concern among scientists was spooking the public before it understood a key distinction in gene editing.
Alexis Pedrick: There are two kinds of gene editing: somatic and germline. Somatic editing means changing the DNA of your somatic cells: hair, blood, skin, everything except your reproductive cells, aka your sperm or your eggs.
Francoise Baylis: So making changes to your somatic cells doesn’t have an impact on your progeny: on the next generation, on your children or their children. It means that if something goes terribly wrong; you haven’t affected a whole lineage.
Alexis Pedrick: Germline editing does change the DNA of the reproductive cells.
Francoise Baylis: So we’re trying to make changes to the gametes: sperm and egg, or possibly the very early human embryo. And the goal there is to make sure that whatever genetic changes are made to those cells, they will in fact be passed on from generation to generation to generation.
Alexis Pedrick: Germline editing is also called “heritable human genome editing.” One of the key distinctions of germline editing has to do with who, or rather, what, you are treating.
Francoise Baylis: You don’t have a patient in front of you. What you have are cells, and you’re trying to make changes to those cells in order to have an impact on subsequent generations.
Alexis Pedrick: When people have dreams about curing a single patient with a genetic disease, they’re thinking of somatic editing. When they have nightmares about creating a race of genetically modified superhumans, they’re most likely thinking about germline editing.
Francoise Baylis: And it’s in that context that people are really worried about the prospect of what could be opened up and how people might be tempted now to think not so much in terms of treatments, but perhaps in terms of enhancements.
Now, I want to be clear, you could do enhancements with somatic genome editing and with heritable human genome editing. But the cultural imagination here is really stuck on this idea that we will build, you know, super athletes or super armies or what have you. And so there’s this idea that we would be going down a very risky path.
Alexis Pedrick: When the Protein and Cell article came out, some scientists who were developing somatic editing therapies for patients with genetic diseases wanted to distinguish themselves from anyone trying to do germline editing. And there was a clear message from them.
Francoise Baylis: “Don’t edit the germline.” So it’s really clear it’s saying, “This is not research that should be done.” And their worry is that if you go down this path, if you start manipulating the reproductive cells, if you’re trying to have an impact on future generations, you’re going to mess it up for us. And basically, they’re really concerned that you’re going to get the public exercised and upset, and then they’ll turn against all genome editing without understanding the difference between making modifications to somatic cells versus making modifications to germ cells.
Alexis Pedrick: But there was also a more favorable view of germline editing.
Francoise Baylis: The other commentary is a little bit more optimistic, shall we say. They’re saying we ought to be able to go forward, but to do so we need to be careful. And so they talk about a prudent pathway forward. So they are saying, “Look, it’s a little premature to think that we would go down this path, but it’s not inconceivable. And it’s also not necessarily wrong, and a simple way to think about it is one and done.”
And so the idea there is: “Well, what is the point of having parents, who are at risk of having children with a particular genetic disease reproduce, have children with that particular condition and then have to treat those children? Why not eradicate it from that lineage?” Now, there are many reasons to raise concerns about that way of thinking, but that is sort of one of the ideas is that it would be more efficient.
Alexis Pedrick: Remember this comment from a 1977 meeting on recombinant DNA?
Ted Howard – Co-Director of the People’s Business Commission: And just because some scientists say that they don’t want to create a new race of supermen as Adolf Hitler did, doesn’t mean that it’s not going to happen.
Alexis Pedrick: It wasn’t a theoretical future ethical problem anymore. It seemed like the science had finally caught up to the fear. It was happening live and in color right now. That’s why Jennifer Doudna wanted to do something about it. The gathering at Napa was the first step.
Next, she tapped a group of 12 people, including Francoise Baylis, to organize the first International Summit on Human Genome Editing. Ten of the twelve were scientists. Francoise and one other person with a background in health law were the exceptions. The summit took place in December 2015. More than 500 scientists, journalists, ethicists and patients gathered in Washington, D.C..
Francoise Baylis: A statement, if you will, was made by the planning committee after that meeting. And by and large, it says, “Somatic genome editing: that’s great. We know how to do clinical trials with gene therapies. Let’s just go ahead and keep doing what we’re doing. Let’s advance that science.”
Alexis Pedrick: They took a different stand on germline editing. They said it was okay as long as embryos were not implanted.
Francoise Baylis: Moving on to clinical trials, transferring those genetically modified embryos into a woman. It’s very clear that the committee says this should not be done until two conditions are met. So one condition: safety and efficacy.
Alexis Pedrick: This one seemed pretty straightforward. You don’t want to harm anyone, and you want it to work. The second condition was broad societal consensus.
Francoise Baylis: Now, if anybody knows anything about ethics and ethics frameworks, what you’ll appreciate is that that is an extremely simple and, some might even say, naïve ethics framework because it only has two elements. And typically ethics frameworks have many, many more conditions, if you will, or criteria that have to be satisfied. But what I think is really wonderful about this framework, if you will, is that it’s very simple, and yet it’s also very complex.
Alexis Pedrick: Even the first condition, which is so basic, is more complicated than it sounds.
Francoise Baylis: It’s never going to be 100% safe. It’s never going to be 100% effective. So somebody is going to have to make a decision about “safe enough, effective enough.” And that’s where the values come in.
Alexis Pedrick: And then there’s the second condition: broad societal consensus. It sounds like a worthy goal. But is it achievable?
Francoise Baylis: If you’re thinking about this on a global stage, we may never reach consensus. We may never get to that point of unity. But I maintain, and I insist, with a lot of confidence, that we’ll all be better off for having tried.
Alexis Pedrick: Better off, perhaps. But it still seems impossible. Matthew Cobb says it’s because of a misconception about the scientific community.
Matthew Cobb: I mean, this is a deceptive word because there is no community. You know, this is a, well, “the scientific community” that suggests there’s a group with common interests. There’s a group with common techniques. But that’s a trade, right? That’s not a community.
Alexis Pedrick: But the summit arrived at an agreement. They said they wanted a, quote, “prudent path forward to proceed with caution.”
Matthew Cobb: Amber light for—your yellow light forgene editing, for embryo gene editing, in other words. Yeah, okay. It could be good. Just be careful. But go ahead.
Alexis Pedrick: Matthew Cobb was not particularly impressed.
Matthew Cobb: It didn’t get to the real issues. Why are you wanting to do this? What are you trying to cure? And that fundamental question—what is the point of this—was never actually addressed.
Alexis Pedrick: And that question would soon prove to be really important.
Chapter Three. The First CRISPR Babies.
Alexis Pedrick: In April of 2018, Marilynn Marchione was the chief medical writer for the Associated Press when she was tipped off by a source about an explosive story.
Marilynn Marchione: He mentioned that there was this possibility that a scientist in China had done germline gene editing. He said there might be a pregnancy underway, but no details. So, I was a bit in limbo until I got more information.
Alexis Pedrick: It would be four months before she learned more. In August of 2018, a second source gave her the details the first one had left out. A Chinese scientist named He Jiankui claimed he had edited embryos using CRISPR. The edits were to make the embryos resistant to HIV. He Jiankui had implanted the embryos into a woman, and she was pregnant with twins. The father was HIV-positive.
Marilynn Marchione: The very first question for us was, “Was this real or was it a hoax?” When you claim to have done something totally unusual or totally extraordinary, you have a higher burden of proof because it is simply your claim; you need to produce corollary evidence. You need to show us science, scientific publications. You can’t just make a wild claim, which is how this sounded initially.
Alexis Pedrick: In October, Marchione and her team went to Shenzhen, China to interview He Jiankui. He agreed to talk to the Associated Press exclusively. Red flags appeared immediately. For one, the ethics panel that approved the experiment was from a different hospital than the one where the gene editing and implanting took place.
Marilynn Marchione: There were other questions about how he went about what he did that made us concerned, and the concerns deepened. He promised to publish animal research on embryo editing, and that never happened. So as we went along, we were getting more and more concerned about had this man actually done what he claimed.
Alexis Pedrick: When she returned home, Marchione got word that the twins had been born. He Jiankui said he would sequence their genomes and send his manuscript to a journal for publication. Marchione got the manuscript before it was published, and she had permission to share it with a scientist to verify that it was real.
Marilynn Marchione: I, as a layperson, couldn’t look at these genetic sequences and say, “Oh, he did this, or oh, he did that.” It’s very important that there be peer review of his work. So when I shared, and I insisted that we be able to do our own outside peer review, that we go to experts like Doctor Musunuru to look at the science and tell us what had happened.
Alexis Pedrick: Doctor Musunuru is the cardiologist and gene editing expert we heard from earlier. He agreed to look over the manuscript and keep the story a secret.
Kiran Musunuru: She finally sends it to me, and I see the headline. I can’t remember exactly what the headline is off the top of my head, but something to the effect, you know, “Gene Edited Twins Resistant to HIV.” Something along those lines, making it very, very clear that this was the result of embryo editing.
And at that point, like my jaw is dropping, and I’m, you know, like getting very, very upset. Then I start looking through the manuscript, and I look at the data, and once I actually look at the pictures that are at the back of the manuscript within milliseconds, I could tell it had gone terribly wrong.
Alexis Pedrick: The pictures that Musunuru is talking about are chromatograms, essentially graphs that show DNA sequencing. They’re visual representations of the DNA edits He Jiankui had done. And crucially, it was a way to see if his edits went as he intended them to go.
You see, there are a few ways that gene editing can go wrong, but the two most common ones are off-target edits and mosaicism. Off-target edits have been described as collateral damage. Say you’re making an edit somewhere in a manuscript, but as you go, you unintentionally make a new typo.
This is Matthew Cobb.
Matthew Cobb: There’s been a lot of realization that, you know, this pair of scissors, in some circumstances, can look like a chainsaw gone amok, and you end up losing loads and loads of DNA sequences. You know, if you’re working in a mouse, it doesn’t really matter because you’re just, you know, the embryo will die, and you’ll get another mouse and eventually you’ll find, uh,be able to make it work. If you’re dealing with human beings, it’s clearly rather a different kettle of fish.
Alexis Pedrick: Mosaicism is when the editing is inconsistent throughout all of the cells in the body. Imagine doing “find and replace” to fix a misspelled word, but only some of the words are corrected. The others are left as is.
Here’s Kiran Musunuru.
Kiran Musunuru: That’s an issue where you start with one cell, single-cell embryo. You inject with CRISPR. That cell starts to divide in the dish very quickly, becomes two cells, then becomes four cells, then becomes eight cells. The problem is CRISPR sticks around. It doesn’t go away instantaneously. So, you might have that initial cell, and maybe CRISPR hasn’t done anything yet. Then it splits into two cells. And now CRISPR makes an edit in one cell but not the other cell. And then you have the cells divide even further and further.
And what ends up happening is you have a patchwork where some cells have edits. Maybe they have the desired edit, the one that you want. Other cells have off-target edits or undesired edits, and then yet other cells may have no edit at all.
Alexis Pedrick: The chromatograms Musunuru was looking at showed the worst-case scenario. The twin girls had both off-target edits and mosaicism. The chainsaw had run amok.
Kiran Musunuru: Whatever He Jiankui thought was going on, it was horrible. And the fact that there were actually two live-born twin girls who had genomes that looked like what was in this, in this paper, you know, made me start crying and screaming in my office because I couldn’t believe it. Just the enormity of it, that someone is playing with human life so cheaply, so egregiously.
Alexis Pedrick: He Jiankui had already done embryonic sequencing before he implanted them. Theoretically, he should have been able to see that there were issues with the CRISPR editing then, yet he went ahead and implanted them. Why?
Kiran Musunuru: And this is part of why I was screaming after I saw the data and yelling and crying and everything… It’s two equally bad possibilities. One, he knew exactly what the data meant. He saw the chromatograms and interpreted them properly. Didn’t care. It was just so…such a horrible human being like you know, “I so badly want to be the first to do this and get all the fame and glory and maybe riches, that I’m just going to go ahead and establish the pregnancy and, you know, pass that milestone, even if it looks horrible.” From a scientific perspective, that’s one possibility.
And that’s what I initially favored because I couldn’t wrap my head around the second possibility, which is he’s so incompetent that he’s viewing these chromatograms and doesn’t actually realize something is wrong. And maybe it’s slightly less bad, but, you know, doing things out of ignorance or negligence is still very, very, very bad when you’re dealing with human life, especially dealing with newborn babies.
Alexis Pedrick: At this point, Musunuru knew what he had to do next.
Kiran Musunuru: I called Marilynn and said, “I’m absolutely, 100% sure this is real. And that’s because if this is fake, there’s no way you could fake such terrible-looking data.” I tried later, just as sort of a thought. I tried in my laboratory. I said, “Let me try to fake these.” I couldn’t fake it. Like it was the real deal. He had done it, and he had done it horribly wrong.
Alexis Pedrick: Musunuru gave an interview to the Associated Press, but the story was still under wraps. Nothing had been published yet, so he couldn’t talk to anyone else about it.
Kiran Musunuru: She had sworn me to confidentiality, so I honored that. I didn’t tell anyone, even though it was eating me up inside, and it was clear that he was going to make an announcement soon. But it wasn’t clear how soon. And as each day goes by, I’m getting more and more anxious, not knowing ethically: “What am I supposed to do there?” You know, there’s human life involved here, right? And if somebody doesn’t say anything like he could be establishing more pregnancies and be doing more of this.
It was really eating at me. And people could tell that something was really, really bothering me. You know, friends and family and whatnot. So, it was not at all a pleasant time.
Marilynn Marchione: I remember having the shakes a lot when I worked on the story. It just, it’s truly a line in the sand. It’s hard to say that you can imagine someone taking that step.
Alexis Pedrick: But someone did. And those fundamental questions that Matthew Cobb brought up loomed in the background. Why are you wanting to do this? What are you trying to cure?
Chapter Four. The Unmet Medical Need.
Alexis Pedrick: Right around this time, the second International Summit on Human Genome Editing was set to happen in Hong Kong from November 27th through the 29th. Marilynn Marchione made plans to go.
Marilynn Marchione: At the time that I booked my flight and made my plans to go to the conference, JK was not on the schedule. There were just other experts in the field, and I thought, “This is a perfect opportunity to find out if anyone knows that this has happened or been going on.” By the time I went, he had been invited. I think there was an effort to include more Chinese scientists because the conference was in China, so he was a late addition.
Kiran Musunuru: There’s some real question whether he was going to unveil it to the world then, almost like an Apple-Steve Jobs type thing: talking about some pretty mundane, fundamental scientific research and then pulling out the one more thing and saying, “By the way, we’ve actually edited embryos. And by the way, we actually have these beautiful twin girls who have been born.” Like that would have dropped, like, you can imagine, like a big rock, you know, in the ocean, like, “Bam!” Like that would have gotten so much attention.
Marilynn Marchione: By the time I landed Sunday night in Hong Kong, I went to the hotel, went to sleep. I woke up. But another story had been published detailing a posting that JK had made.
Alexis Pedrick: A headline in the MIT Technology Review read, “Exclusive Chinese Scientists are Creating CRISPR Babies.” Marchione had been scooped.
Marilynn Marchione: So JK had published something that put some of this in the public domain. And at that point, you know, it’s out there. All bets are off.
Alexis Pedrick: The story revealed what Marchione already knew: that He Jiankui and his team had been using CRISPR to edit embryos to disable the CCR5 gene.
Matthew Cobb: What he was trying to do was to alter a gene which is associated with resistance to HIV. It doesn’t mean you are immune to HIV, but it means you’re less likely to catch it.
Alexis Pedrick: The article was published on November 25th. By the time everyone got to Hong Kong, they all knew about the story. Here’s Francoise again.
Francoise Baylis: Whatever had been planned, the buzz is all about what’s happened. “Who did this? Are these children alive? Are they well? Is anyone else doing this?” So, it really takes over the conversation. And this is before the meeting gets started.
Alexis Pedrick: A day after the MIT Technology Review story came out, the Associated Press hit publish on Marilynn Marchione’s story.
Marilynn Marchione: It wasn’t a race to publication. I know that some people view it that way. I felt as if we had a great deal more information about this case, including the sort of flaws in the science that supposedly the ethics panel that had approved this experiment was not even the hospital where the work was done.
There were many, many questions about what he had done and how he had gone about it. So, we had a much more complete accounting and more detail to bring to the table and to share with the public at that point. And I’m really proud of that work. It—thousands and thousands of words, tens of thousands of words. At this point, not a single correction. Our report has stood the test of time.
Alexis Pedrick: At this point, the public was aware of He Jiankui’s claims, that there were seven couples who went through embryo editing in IVF, and one of the pregnancies had resulted in the birth of twins. They were referred to as “Lulu” and “Nana,” but these are not their real names. And no one knew the identity of the parents. Marilynn Marchione never even met them. The story set off a frenzy among scientists and ethics watchdogs.
This is Kiran Musunuru again.
Kiran Musunuru: That story of genetic misadventures, if you want to call it that. That story, I think, was in fact the biggest medical story of the century so far.
Alexis Pedrick: In Hong Kong, there was a frenzy in the audience before He Jiankui even went on stage.
2nd International Summit on Human Genome Editing Stream: So just to remind everyone here that we, we want to give Doctor He a chance to explain what he’s done. So please, can you allow him to speak without interruptions? As I said, I have the right to just cancel the, the session if there’s too much noise and interruption.
He Jiankui at 2nd International Summit on Human Genome Editing: Thank you. First, I must apologize that these results leaked unexpected. Taken away from the community of the full data being presented immediately in a scientific value.
Alexis Pedrick: He Jiankui quickly addressed his reason for choosing the CCR5 gene.
He Jiankui at 2nd International Summit on Human Genome Editing: So HIV remains a top ten cause of death in several countries, particularly developing countries. This is a serious unmet need as an infection. Severity is often made even worse by discrimination.
Alexis Pedrick: And he shared his pride in the experiment, speaking specifically about the twins’ father, who was HIV positive.
He Jiankui at 2nd International Summit on Human Genome Editing: I feel proud, actually, because he lost the hope for the life. But when the baby was born and with the protection, he receive the message at the day of birth say, “I will work hard, earn money and take care” of his two daughters and his wife.
Alexis Pedrick: There were 500 people at the summit and nearly 2 million more were watching on the live stream. Matthew Cobb was one of them.
Matthew Cobb: I remember watching this on the live stream and on Twitter, when it was good, because you got people who knew what they were talking about. Watching the live stream and then hammering out tweets describing what was happening. It became immediately very, very obvious that something had gone horribly wrong.
Alexis Pedrick: It seemed that everyone from Matthew Cobb to the audience in Hong Kong to the people online had all reached the same conclusion that Kiran Musunuru did.
Matthew Cobb: The crappy data that he was presenting showed very clearly that the off-target effects were not even consistent, so there were off-target effects. There were other bits of the DNA were affected, and the, the twins were what are called “mosaic.”
The whole point of embryo editing is that every cell, because you start off with one cell: “Let’s change that.” And therefore all the daughter cells, which are all the trillions of cells that make up our bodies, have the same DNA. And this hadn’t happened because it’s an embryo, right? It’s trying to get somewhere. Be something.
Kiran Musunuru: What blows my mind is that he shows the same data that are in the manuscript—the chromatograms—that, to me, look absolutely horrible. And what was immediately clear from things that were put on social media is other experts who were at the international summit were seeing the same images and were also instantly horrified at what they were seeing, which made me think, “Wow, he has no clue that this is making him look so horrible on so many levels.” Negligent, incompetent, just monstrous behavior as a human being.
Alexis Pedrick: After He Jiankui’s presentation, the questions poured in.
2nd International Summit on Human Genome Editing Stream: How were you going to prove the effectiveness of the treatment if the two individuals remain secret?
Alexis Pedrick: He Jiankui responded that it was against Chinese law to disclose the identity of HIV-positive people in public. Other questions were about informed consent.
2nd International Summit on Human Genome Editing Stream: How did you convince the parents when you started this experiment? Did you tell them, like, there’s alternative solutions, for example, other ways to avoid AIDS infection of their child?
Matthew Cobb: And David Liu of Harvard. He asked the most important question.
2nd International Summit on Human Genome Editing Stream: So could you first describe what is the unmet medical need, not of HIV in general, which I think we all appreciate, but what is the unmet medical need for these patients in particular?
Matthew Cobb: What was the unmet clinical need? And He Jiankui hasn’t got an answer. But, you know, before you do any biomedical intervention, you have to be sure this is the, the best thing for that patient. But these weren’t patients. These were two normal, or they were going to be two normal girls. Their embryos, you know,their DNA was as normal as anybody else’s. Right? And now they’ve been mutated.
So, there was no clinical need. They had none. If they didn’t want to get HIV when they’re older, well, that’s relatively easy to do. As I say to my students, you all know how not to get HIV. It’s not rocket science. It doesn’t involve editing your genes. There are very simple ways of not getting HIV. So, his starting point was extremely odd. Right?
Alexis Pedrick: He Jiankui claimed that because the father of the girls was HIV-positive, this was a way to make sure his children didn’t have it. But just because you’re HIV-positive doesn’t mean that your offspring will be. And there are a lot of things you can do to avoid that. And beyond that, the fact is that there are other treatment options for HIV.
Kiran Musunuru: You can live full, healthy lives for the most part on these medications. It’s not a death sentence like it was in the 1980s, right? And so it’s really hard to make an argument that, “Wow, by turning off this gene and making people more resistant to infection with HIV, that we’re filling a desperate medical need here.”
Because the fact of the matter is, you’re not. So why on earth do you need to mess with embryos? It’s like, it’s just so disproportionate. The potential for benefit is so low, and the risks are so high.
Alexis Pedrick: He Jiankui didn’t have any satisfying answers to these big questions. It seemed like he hadn’t even seen them coming. He was convinced and was trying to convince others that this edit had been medically necessary, but it actually seemed more like an enhancement: something dangerously close to that 1977 fear of creating a race of supermen. Here’s Hank Greely again.
Hank Greely: He thought he was going to be welcomed as a revolutionary scientist, and he was shocked to discover he hadn’t become famous. He had become infamous. He clearly hadn’t thought this through. And ultimately he got angry and stomped off. And that was the last time anybody saw him in public for over—for nearly four years.
Chapter Five. Piecing Together What Happened After the Summit.
Alexis Pedrick: Scientists and the media started to scrutinize what had happened. One of the most alarming things about the experiment was the process of getting informed consent.
Kiran Musunuru: Like, it breaks every ethical principle of medical research to do things in the way that he did. If you look at the informed consent document that he’s prepared for the patients in his clinical trial, it reads more like a contract. And there’s language in there that basically exonerates He Jiankui and his team from any bad thing that happens. That is not what an informed consent document ever is supposed to say. So, this was a mockery of a clinical trial.
Alexis Pedrick: Then there was how he recruited the patients. In China, it’s illegal for people with HIV to get IVF. So under normal circumstances, it wouldn’t have been an option for Lulu and Nana’s parents because of the father’s HIV status.
Kiran Musunuru: So, here He Jiankui was offering, “Hey, sign up for this clinical trial. And it’s kind of a loophole. You can actually have kids after all. The only thing you have to do is let me work on those embryos and edit these embryos. But you know what? That’s even better, because not only will you get to have kids, you’ll have kids who are immune to HIV.” So that’s how he sold this bill of goods.
Alexis Pedrick: To Marchione, it seemed like the parents were just trying to have a kid any way they could. They weren’t in it for the gene editing.
Marilynn Marchione: It would be like if you were a prisoner, and they offered you food and you’d been starving.
Alexis Pedrick: Under informed consent rules in the U.S., participants would be permitted to leave any time for any reason. This agreement was different.
Kiran Musunuru: It says: “If you withdraw from the trial, you owe us money. You have to pay back all the health care.” You potentially have to pay back a penalty, a monetary penalty that’s much higher than the average annual income of a citizen of China.
Marilynn Marchione: The consent forms also concern themselves with things that I’ve never seen before in scientific documents. Like, “You must agree to photographs with me, the researcher, and you must agree to, you know, this kind of publicity.”
Alexis Pedrick: But the issues went beyond just informed consent. In fact, if we go all the way back to the beginning, there was a big question that needs an answer. Was He Jiankui the best person to do an experiment like this?
We use the broad term “scientists” a lot, but in the practice of science, in the practice of editing DNA, specificity matters. And He Jiankui is not a geneticist. He’s a biophysicist.
Kiran Musunuru: Under no circumstance would you consider him appropriate. Not a physician, no experience with clinical trials, not even a very good scientist. Taking it upon himself to run a clinical trial.
Alexis Pedrick: Still, the story in the scientific community was that He Jiankui was a lone, bad actor. But we talk a lot about the collaborative nature of science. Those summits and conferences and meetings are all a demonstration of that. And so, in addition to the issues with informed consent, He Jiankui’s scientific background, is also the question of how “alone” one scientist can truly be.
Here’s Francoise Baylis.
Francoise Baylis: He Jiankui was not a rogue scientist. He did exactly what a scientist is trained to do, which is to be ahead of the pack and to be bold and to make those innovative moves to be the first. I mean, that’s how you get a Nobel Prize. You don’t get a Nobel Prize for following the pack.
And I also think it’s important to remember that, you know, he studied and was trained in the United States. Some people, it’s not clear and it may never be clear, knew what he was doing. And many of these people were in the United States, and they didn’t stop him.
Alexis Pedrick: He Jiankui had studied in the United States at Rice University and Stanford. And he told several well-known geneticists from these institutions what he was planning on doing. And while they disapproved of it, no one tried to stop him. So didn’t they have a responsibility to warn someone? It turns out it’s easier said than done.
Kiran Musunuru: There’s no, like, there’s no police. You can, you know, inform, like, “Hey, there’s this bad stuff going on in China. And someone might be, you know, establishing pregnancies within embryos. You should, you know, go do something about it.” Right? And it’s not like I can, like, talk to someone in the Chinese government. Like, I wouldn’t even know where to start.
Alexis Pedrick: Before he learned about He Jiankui from Marilynn Marchione, Kiran Musunuru did try to communicate his concerns over germline editing to his congressional representatives.
Kiran Musunuru: That didn’t get much traction. I think the people I were talking to, congressional staffers and things like that, were more interested in hearing about the positive aspects of CRISPR.
Alexis Pedrick: Here’s Francoise Baylis again.
Francoise Baylis: You don’t get to walk away by saying, “I didn’t have a number to call.” And the reason I say that is all you had to do is pick up the phone and call any major newspaper. It was a scoop. It was a story. Do you really believe that no newspaper would have wanted to investigate this and to have been first to say, “This is happening.”? So, there were options.
Alexis Pedrick: Scientists chose not to say anything when they had the chance. Baylis says that perhaps it’s worth questioning scientific norms.
Francoise Baylis: We need to look at the way in which we do science, the things that are normalized in terms of science. And so one of the things is you don’t rat out your colleague. You know? There are some scientists around this particular case who have said, you know, “This was told to me in confidence, and therefore I’m going to respect that confidence. And it’s not up to me to tell the world what he’s doing.” Well, why is that the norm?
Alexis Pedrick: And what about the scientific community as a whole? Don’t they bear some of the responsibility? Matthew Cobb says the gatherings at Napa and Washington, D.C. missed the boat on the safety issue.
Matthew Cobb: They just kind of assumed: “Yeah, it’s a pair of scissors. Right? What harm can you do with a pair of scissors?” Well, you don’t want to have a crazy person in your house with a pair of scissors. They can do a lot of harm.
Alexis Pedrick: Musunuru thinks scientists at those meetings should have taken a firmer stand against germline editing.
Kiran Musunuru: I think that would have been more effective if they had unilaterally said, “Look, we do not know what we’re doing. We do not understand the safety risks. There should be a moratorium for an indefinite amount of time until we get a better grasp on things.”
They did not do that at either of these international summits. They were much more equivocal in their language and saying, “Well, maybe this might be useful. Maybe there’s a path forward. We don’t think it’s there yet. But, you know, maybe there’s this checklist of things, and if you check off enough things, then you can go forward.” And that was the wrong move, because at least the way he tells it, he took that checklist and said, “Oh, I think I’ve checked off everything, so I think I’m fine.”
Alexis Pedrick: Francoise Baylis says that this episode should serve as a lesson for scientists.
Francoise Baylis: We should not necessarily think about blame in terms of finger-pointing, but think about it as an opportunity for genuine, critical self-reflection. What could we, as a scientific community, have done differently that would have created an environment that would have been different? And being different in this case might just have been, you weren’t doing this science as a big secret, right? Like if you’re doing science as a secret, why? It’s because you don’t want to be scooped.
And so I think it’s really important for the scientific community as a whole to take responsibility and to think about the ways in which it keeps advocating for self-governance: “We can take care of this. We know how to police ourselves.” And yet, at the same time, you have these kinds of failures. Now you can, and people have, just pointed to the one case: that one bad apple. But I think we really ought to look at the container, the bushel. What’s the bushel holding? Both these good and bad apples.
Alexis Pedrick: One year after the Hong Kong summit, this story broke.
CBS This Morning, Dec. 30, 2019: So a Chinese scientist helped create the world’s first genetically edited babies. He is going to jail. His name is He Jiankui of China. He is going to be in prison for three years for carrying out what the Chinese government says were illegal medical practices.
Alexis Pedrick: The Chinese government was clearly not interested in examining the bushel. They went for the one specific bad apple. He Jiankui was charged with practicing medicine illegally and violating scientific regulations and norms. He was in prison for three years, but recently he started making news again.
Caiwei Chen: I started noticing a lot of his posts going viral.
Alexis Pedrick: This is Caiwei Chen, the China reporter for the MIT Technology Review.
Caiwei Chen: And it’s usually one quote. Like one very like, I would say provocative and controversial, almost rage-baiting statement. Well, sometimes it’s just nonsensical and very crass. But the other times it is straight up offensive or provocative.
Alexis Pedrick: Here are some of his posts, which are often accompanied by a picture of him staring into the camera or off into the distance. “Pursuing forbidden knowledge is innovation.” “Great revolution begins with controversy.” “Ethics is holding back scientific innovation and progress.”
In another, he says, “If I had to do it all over again, I would do exactly the same thing.” They’re so surreal that they seem like a parody or fake. But Chen confirmed that they were in fact him, and they were very real.
Caiwei Chen: I think we emailed him at the time, and he admitted that it was him.
Alexis Pedrick: The concerning part is that he’s getting the attention he is so clearly seeking.
Caiwei Chen: I do think you’re noticing a real and emerging phenomenon, which is like there is an appetite for this type of like “boundary pushing,” to put it in a nice way. There are a lot of alternative thinkers and this, like, niche market, at least curious or interested in designer babies.
Alexis Pedrick: Which makes other scientists really worried that He Jiankui is more emboldened than ever that he might try it again if he hasn’t already. Some also worry that CRISPR’s reputation has been tarnished. Kiran Musunuru has worked hard against that narrative for weeks after the articles were published in 2018. He gave interviews sharing what he knew and hammering this message.
Kiran Musunuru: You know, it’s not all bad. This doesn’t condemn CRISPR. The concern was that legislators, for example, would say CRISPR is bad. Like, “This is horrible. We’re just going to ban the use of CRISPR for any sort of medical applications altogether.” To their credit, legislators did not do it. They seem to understand that there was some nuance there.
Alexis Pedrick: And that’s a good thing for all of us. And Musunuru in particular, because he was about to have one of the biggest CRISPR breakthroughs yet.
CBS Mornings, May 16, 2025 : In this morning’s Health Watch, a historical medical breakthrough: a baby named K.J., born with a rare genetic disorder, is the first person in the world to be successfully treated with a tailor-made gene therapy.
Alexis Pedrick: Musunuru developed the treatment for Baby KJ, which to be clear, was somatic gene editing, to meet an otherwise unmet medical need.
As someone who has seen all sides of what CRISPR can do, Kiran Musunuru has done some reflecting.
Kiran Musunuru: And so the lesson that I’ve taken out of this is that, you know, you can be as noble as you want and really, like, try so hard to persuade your peers that this is the right way to do things and maybe even mobilize a lot of them and start to talk about self-regulation. And we need moratoriums, or we need to do things in a thoughtful, careful, rigorous way. But it isn’t that effective.
Kiran Musunuru: There’s no guarantee that’s going to be effective. The better way to do it, honestly, is legislation and regulation.
Alexis Pedrick: Distillations podcast is produced by the Science History Institute and recorded in the Laurie J. Landau Digital Production Studios.
Our executive producer is Mariel Carr. Our producer is Rigoberto Hernandez. Our associate producer is Sarah Kaplan, and our sound designer is Samia Bouzid. This episode was reported and produced by Mariel Carr and Rigoberto Hernandez.
Support for Distillations has been provided by the Middleton Foundation and the Wyncote Foundation. You can find all of our podcasts, as well as our videos and articles, on our website at sciencehistory.org. And you can follow us on social media @scihistoryorg for news about our podcast and everything else going on in our free museum and library.
For Distillations, I’m Alexis Pedrick. Thanks for listening.
