Exploring the scientific, ethical, and societal implications of the world's first gene-edited babies created using CRISPR technology
On November 29, 2018, the world of science stood still. At the Second International Summit on Human Genome Editing in Hong Kong, Chinese scientist Jiankui He announced he had created something unprecedented—the world's first genetically edited babies 1 .
The scientific community reacted with immediate shock and overwhelming condemnation. Within days, the Chinese Academy of Medical Sciences declared opposition to this "illegal behavior" 1 .
Multiple governments and scientific bodies issued statements against the experiment
He Jiankui was dismissed from his university position and faced legal action
International calls for stronger oversight and guidelines for gene editing research
Widespread media coverage sparked global discussion about genetic engineering ethics
To understand why He Jiankui's experiment sparked such controversy, we must first appreciate the revolutionary tool that made it possible: CRISPR-Cas9. Often described as "genetic scissors," this technology allows scientists to make precise changes to DNA—the fundamental code of life that directs the development and function of all living organisms.
CRISPR-Cas9: The revolutionary gene-editing tool
Researchers design a guide RNA sequence that matches the specific DNA segment they want to edit.
The guide RNA binds to the Cas9 enzyme, forming a CRISPR-Cas9 complex that can search the genome.
Once the target DNA is located, Cas9 cuts both strands of the DNA double helix at the precise location.
The cell's natural repair mechanisms are activated, allowing researchers to disable, repair, or replace genes.
| Technology | Discovery Period | Key Features | Limitations |
|---|---|---|---|
| Meganucleases | 1990s | First genome editing tools, recognize long DNA sequences | Rare cutting sites, difficult to engineer 2 |
| Zinc Finger Nucleases (ZFNs) | Early 2000s | More programmable than meganucleases | Complex design process, expensive 1 2 |
| TALENs | 2010s | Easier to design than ZFNs | Still relatively costly and time-consuming 1 2 |
| CRISPR-Cas9 | 2012-present | Simple design (using guide RNA), low cost, highly versatile | Off-target effects, delivery challenges 1 2 6 |
He Jiankui, then a scientist at the Southern University of Science and Technology in China, selected a specific genetic target for his human embryo editing experiment: the CCR5 gene 1 . This gene produces a protein that HIV uses to enter and infect immune cells.
He's stated goal was to create children naturally resistant to HIV infection, targeting this gene in embryos created through IVF for couples where the father was HIV-positive 1 .
Function: HIV co-receptor
Goal: Create HIV resistance
Method: Embryo editing
Designing guide RNAs specific to the CCR5 gene sequence
Injecting CRISPR-Cas9 components into human embryos at the single-cell stage
Implanting the edited embryos into the mother's uterus after confirmation of editing
Monitoring the resulting pregnancy and analyzing the genetic outcomes
Genetic analysis revealed that rather than creating the intended precise edit, the CRISPR system had produced a variety of different mutations at the target site.
Even more alarmingly, evidence suggested mosaicism had occurred—where some cells carried the edited genes while others remained unmodified, creating individuals with multiple genetic profiles 1 .
Nearly unanimous criticism from the global scientific community
Multiple Chinese regulations and international ethical guidelines breached
He was dismissed from his position and faced legal consequences
The strong reaction from the scientific community wasn't merely about ethical boundaries—it reflected genuine concerns that the technology wasn't sufficiently advanced for safe use in human reproduction.
The most significant scientific hurdle was—and remains—off-target effects. While CRISPR-Cas9 is precise, it's not perfect. The guide RNA can sometimes bind to DNA sequences similar but not identical to the intended target, resulting in cuts at the wrong locations 1 2 .
These unintended edits could disrupt crucial genes, potentially activating cancer-causing genes or disabling tumor suppressors. As one editorial noted, "Such off-target mutations or other effects could lead to cancer or other diseases in the early or later life of genetically modified babies" 1 .
When CRISPR components are introduced into a newly fertilized egg, they don't always complete their work before the cell begins dividing. This can result in mosaicism, where some cells in the developing embryo carry the edit while others do not 1 .
The consequence is an individual with multiple genetic profiles in different tissues, creating unpredictable and potentially harmful health effects. As one analysis explained, "We are still uncertain what the effects of the gene editing would be in the genome of babies" with mosaic genotypes 1 .
He Jiankui targeted the CCR5 gene based on its well-established role as an HIV co-receptor. However, genes often serve multiple functions in the body. Subsequent research has revealed that CCR5 plays roles in immune response to other pathogens, brain function, and potentially learning and memory 1 .
Removing or disrupting such genes can have unintended consequences that might not become apparent until later in life. As one paper cautioned, "In order to select the perfect target gene and an efficient target site, we need to understand that gene's function well" 1 .
| Concern | Description | Potential Consequences |
|---|---|---|
| Off-target effects | CRISPR editing at unintended locations with similar DNA sequences | Unknown genetic mutations that could cause cancer or other diseases 1 2 |
| Mosaicism | Editing occurs in some but not all cells, creating genetically mixed individuals | Uncertain effectiveness of edits and unpredictable health impacts 1 |
| Unpredictable mutations | The edits created unexpected insertions and deletions at the target site | Potential disruption of other biological functions 1 |
| Incomplete understanding of CCR5 | The gene plays roles beyond HIV infection, including immune and brain functions | Increased susceptibility to other diseases like West Nile virus or lupus nephritis 1 |
While the technical concerns were substantial, the ethical implications of He Jiankui's experiment provoked even deeper concerns about the future of human genetic modification.
Perhaps the most significant ethical distinction in genetic engineering lies between somatic editing (modifying non-reproductive cells in an existing individual) and germline editing (modifying embryos, sperm, or eggs in ways that create heritable changes) 5 .
Somatic edits affect only the individual receiving treatment, while germline edits would be passed down to all future generations, permanently altering the human gene pool. Most ethical frameworks had drawn a bright line at germline modification, arguing that we lack the wisdom to make permanent decisions that affect all descendants of the edited individual 1 5 .
While He Jiankui claimed a medical purpose for his experiment, the same technology could theoretically be used for genetic enhancement—selecting for traits like intelligence, height, or athletic ability.
This raises the alarming prospect of a new form of inequality where the genetically engineered wealthy create a "genetic divide" from unmodified populations 2 5 . As one analysis noted, fears of "extreme inequality caused by its use" represent a major ethical concern surrounding CRISPR technology 2 .
The global regulation of germline editing remains a patchwork of different standards and enforcement mechanisms. Some countries explicitly prohibit germline editing, others have ambiguous regulations, and a few have permissive environments 5 .
This creates the potential for "reproductive tourism"—where individuals travel to countries with lenient regulations to access prohibited technologies 5 . The need for international coordination and standards was highlighted by He's experiment, which violated Chinese regulations but raised questions about how to prevent similar actions in jurisdictions with weaker oversight.
At the deepest level, germline editing forces us to confront fundamental questions about what it means to be human and whether we have the wisdom to redesign our own species.
As one paper exploring the ethical dimensions noted, these concerns "stem from the fear of defying nature" 2 . Many philosophical and religious traditions question whether humanity should assume the role of creator, arguing that such power might ultimately undermine essential aspects of human dignity and identity.
In the years since the controversial birth of the first gene-edited babies, the scientific community has worked to establish clearer guidelines for how—and whether—to proceed with human germline editing.
Prominent scientists and ethicists have called for a global moratorium on clinical uses of germline editing until technical safety concerns can be resolved and societal consensus reached on appropriate applications 5 .
The 2019 statement from the Chinese Academy of Medical Sciences exemplifies this cautious approach, opposing "any clinical operation of human embryo genome editing for reproductive purposes in violation of laws, regulations, and ethical norms" 1 .
While reproductive applications remain off-limits, basic research on human germline editing continues under strict oversight in many countries. This research aims to address the technical challenges that made He Jiankui's experiment premature, including:
There's growing recognition that decisions about germline editing shouldn't be left to scientists alone. As one analysis recommended, we need "greater regulations placed on CRISPR and gene editing as a whole to ensure human safety" 2 .
This includes engaging diverse publics in discussions about what applications—if any—should be permitted, and establishing international governance structures to prevent rogue applications while enabling beneficial medical research.
Since the 2018 controversy, the field has witnessed both caution and progress. In 2023, the first CRISPR-based therapy for sickle cell disease received regulatory approval, demonstrating the technology's legitimate therapeutic potential when applied to somatic cells 2 .
More recently, in 2025, news emerged of a successful personalized CRISPR therapy given to a baby with a genetic disease, though details about this case remain limited 4 . These developments highlight the ongoing advancement of CRISPR technologies within ethical boundaries.
| Research Tool | Function | Application in Gene Editing |
|---|---|---|
| Cas9 Nuclease | Cuts DNA at specific locations | Creates double-strand breaks for gene knockout or insertion 3 7 |
| Guide RNA | Directs Cas9 to target sequence | Determines specificity of gene editing 3 9 |
| Delivery Vectors | Transport editing components into cells | Viral vectors (AAV, lentivirus) or non-viral methods (electroporation) 3 |
| Donor DNA Template | Provides correct sequence for repair | Enables precise gene corrections or insertions 9 |
| Cell Culture Systems | Supports growth of edited cells | Allows expansion and study of modified cells 3 |
The story of the first gene-edited babies represents a complex intersection of scientific ambition, ethical boundaries, and societal values. While CRISPR-Cas9 offers tremendous potential for addressing genetic diseases, the 2018 experiment demonstrated how not to advance this promising field—through secrecy, ethical shortcuts, and premature application of immature technology.
The strong negative response from the scientific community wasn't merely about stopping progress but about ensuring that if and when human germline editing proceeds, it does so with adequate safety data, transparent oversight, and broad societal consensus.
As one editorial bluntly stated, the birth of the first CRISPR babies was "irresponsible and too early" 1 . This event serves as a cautionary tale about scientific hubris and the importance of maintaining public trust.
The question is rarely whether we can do something, but whether we should.
As we stand at this technological frontier, the path forward requires balancing the genuine promise of preventing suffering with the profound responsibility of shepherding a technology that could permanently alter the human future. The story of the first gene-edited babies may ultimately serve as a pivotal lesson in how humanity navigates its growing power to reshape life itself.