Genetically modifying a human involves altering DNA in reproductive cells like sperm, eggs, or an embryo, making the changes heritable. This process, known as germline editing, allows genetic modifications to be passed down through generations. For decades, this remained a theoretical possibility, a subject of intense debate.
As gene-editing tools grew more sophisticated, the conversation moved from “if” to “when,” prompting discussions about the moral and societal lines that should not be crossed. The power to reshape the human gene pool raised concerns about unforeseen health consequences, social equity, and the definition of what it means to be human.
The He Jiankui Experiment
In November 2018, the scientific community and the world were stunned by an announcement from Chinese scientist He Jiankui. Through YouTube videos, He declared that his research team had created the world’s first genetically edited babies. This claim, which broke a long-held taboo in science, was made just before the Second International Summit on Human Genome Editing in Hong Kong, ensuring maximum visibility.
The experiment, conducted in secrecy at the Southern University of Science and Technology in Shenzhen, involved twin girls given the pseudonyms Lulu and Nana. He’s project recruited couples where the father was HIV-positive and the mother was not, offering them in vitro fertilization (IVF) combined with the experimental gene-editing procedure. The work had not been published in a peer-reviewed scientific journal, meaning it lacked the independent verification standard for such research.
The revelation was a shock because it bypassed years of global consensus-building about the ethics of such an experiment. He and his collaborators reportedly forged ethical review documents to proceed, misleading doctors involved in the IVF process. The news broke first in the MIT Technology Review, compelling He to make his public announcement and setting off widespread condemnation.
The Intended Genetic Change and Technology Used
The specific goal of the experiment was to alter the CCR5 gene. This gene provides the instructions for a protein that acts as a doorway, allowing the most common strain of HIV to enter immune cells. A rare, naturally occurring mutation in this gene, known as CCR5-Δ32, can result in resistance to HIV infection. He Jiankui’s stated aim was to recreate this effect for the embryos, theoretically granting the children lifelong protection against the virus.
To achieve this, the research team used the gene-editing tool CRISPR-Cas9. Often described as “molecular scissors,” CRISPR-Cas9 can be programmed to locate a specific sequence in the genome, cut the DNA, and allow the cell’s natural repair mechanisms to make a change. The goal was to disable the CCR5 gene in the embryos shortly after fertilization.
This procedure differs from somatic gene therapy, which targets non-reproductive cells in a patient and affects only that individual, without being passed to future generations.
The experiment, however, did not successfully replicate the desired CCR5-Δ32 mutation. Instead, it created new, novel mutations whose effects are unknown. Data later revealed the edits were not present in all of the girls’ cells, a condition called mosaicism. This means they may not have the intended HIV resistance and highlighted the immaturity of the technology for this application.
Global Reaction and Ethical Concerns
The response to He Jiankui’s announcement was swift and overwhelmingly negative. Leading scientists, medical organizations, and bioethicists worldwide condemned the experiment as a dangerous and unethical departure from established scientific norms. More than 122 Chinese scientists issued a joint statement calling the experiment “crazy” and a blow to the reputation of Chinese science.
A central ethical failure was the lack of transparency and a legitimate ethics review. The approval for the study allegedly came from a private hospital and involved forged documents, circumventing proper oversight. The informed consent process was also deeply flawed, as the forms were long, technical, and in English, making it questionable whether participants understood the profound risks.
There was also no clear medical need for the procedure. Well-established methods already exist to prevent HIV transmission during IVF, making the high-risk, experimental approach unjustifiable. Scientists raised serious concerns about the physical risks to the children, including “off-target” edits where CRISPR might accidentally alter other parts of the genome. The heritable nature of the changes was also a major point of criticism.
Consequences and Current Understanding
The aftermath of the experiment brought severe consequences for He Jiankui. Chinese authorities launched an investigation, and He was fired from his position at the Southern University of Science and Technology. In December 2019, a Chinese court sentenced him to three years in prison and a significant fine for “illegal medical practices.” Two of his collaborators also received lesser sentences.
The current health and status of the twin girls, Lulu and Nana, and a third genetically edited child born later, are not publicly known. Information about them is limited due to privacy concerns, and they are being monitored by the state. The scientific community remains worried about their long-term health, as the intended benefit of HIV resistance is uncertain while the risks of unforeseen health issues remain.
This event had a profound impact on the field of gene editing. It triggered urgent calls for stricter international regulations and a potential moratorium on heritable human genome editing. The experiment served as a lesson on the dangers of scientific ambition outpacing ethical consideration, highlighting the necessity of robust oversight.