No one has ever created a cloned human being. Despite decades of speculation, several high-profile hoaxes, and genuine advances in the underlying technology, no verifiable case of a cloned person being born has occurred. What has happened is more nuanced: scientists have successfully used cloning techniques to produce human embryonic stem cells in a laboratory dish, and they have cloned non-human primates to live birth. The distance between those achievements and producing a cloned human baby remains enormous, blocked by biological obstacles, near-universal legal prohibitions, and deep ethical objections.
The Fraud That Set Everything Back
The most famous claim of human cloning turned out to be entirely fabricated. In 2004 and 2005, South Korean researcher Woo Suk Hwang published two papers in the journal Science announcing that his team had derived human embryonic stem cell lines from cloned embryos using a technique called somatic cell nuclear transfer, or SCNT. The papers were treated as landmark achievements. Hwang became a national celebrity in South Korea. Then everything fell apart. Investigations revealed that Hwang’s claims of creating cloned human embryonic stem cell lines were completely fabricated, and that the data and photographs in both papers had been falsified.1Europe PMC / Taylor & Francis. Fraudulent human embryonic stem cell research in South Korea: lessons learned The scandal did real damage to the field. It deepened public skepticism about cloning research, made journal editors far more cautious about SCNT papers, and wasted years during which other researchers might have attracted more funding and attention.
What Scientists Have Actually Achieved
The genuine breakthrough came in 2013, when Shoukhrat Mitalipov’s group at Oregon Health and Science University demonstrated, for the first time, that human somatic cells could be reprogrammed into embryonic stem cells through SCNT. Their method involved taking a donor’s skin cell, removing its nucleus, inserting that nucleus into a human egg cell that had had its own nucleus removed, and then coaxing the resulting cell to begin dividing. The resulting stem cell lines had normal chromosome counts and inherited their nuclear genome exclusively from the donor’s somatic cells.2PubMed Central. Human embryonic stem cells derived by somatic cell nuclear transfer Their gene expression profiles resembled those of stem cells derived from naturally fertilized embryos, suggesting the reprogramming was thorough.3Cell. Human Embryonic Stem Cells Derived by Somatic Cell Nuclear Transfer
This is sometimes loosely called “human cloning,” and technically it is, but only in the therapeutic sense. The embryos were never implanted in a uterus. They were grown to the blastocyst stage (roughly five to seven days of development) for the purpose of harvesting stem cells. No pregnancy was initiated. No baby was born. The distinction between creating stem cells in a dish and creating a living person is the dividing line in this entire field.
Primate Cloning Shows Both Promise and Difficulty
If human reproductive cloning were ever attempted, primate research offers the clearest preview of what to expect. In 2007, researchers successfully produced rhesus macaque embryonic stem cells through SCNT, using adult skin cells as the donor material. That work was proof-of-concept for therapeutic cloning in primates but did not result in live births.4Nature. Producing primate embryonic stem cells by somatic cell nuclear transfer
The bigger milestone came in 2018, when Chinese researchers at the Chinese Academy of Sciences produced the first live-born cloned primates: two macaque monkeys named Zhong Zhong and Hua Hua. The team overcame earlier barriers by injecting molecules that helped the cloned embryos reprogram their gene expression more completely. Using fetal fibroblast donor cells, about 45% of the resulting SCNT embryos developed to the blastocyst stage, and a substantial fraction of those showed healthy inner cell clusters.5Cell. Cloning of Macaque Monkeys by Somatic Cell Nuclear Transfer Even so, the overall efficiency was low: of the many embryos transferred to surrogate mothers, only two monkeys survived to birth. That ratio underscores just how difficult mammalian reproductive cloning remains even under the best laboratory conditions.
Why Cloning a Human Would Be So Hard
The technical barriers to reproductive cloning in humans are severe, and most of them trace back to a single problem: when you take a fully specialized adult cell and try to convince its DNA to start over as if it were a brand-new embryo, the reprogramming is almost always incomplete. Researchers describe this as faulty epigenetic reprogramming, and it is the central reason cloning efficiency in every mammalian species remains low.6PubMed Central. Epigenetic Reprogramming During Somatic Cell Nuclear Transfer: Recent Progress and Future Directions
In primates specifically, the problems compound. When the egg’s own genetic material is removed during the SCNT process, structures called spindles are disrupted. Those spindles are critical for properly distributing chromosomes when cells divide. The result is that cloned primate embryos frequently end up with the wrong number of chromosomes, along with a cascade of other abnormalities involving imprinted genes, mitochondrial mismatches, and asynchronous cell cycles.7Science. Molecular Correlates of Primate Nuclear Transfer Failures8Developmental Biology. Embryogenesis and blastocyst development after somatic cell nuclear transfer in nonhuman primates: overcoming defects caused by meiotic spindle extraction
Even if a cloned embryo survives early development, pregnancy itself is perilous. One of the most consistent findings across cloned cattle, mice, and pigs is placental overgrowth. In cloned mice, abnormally large placentas appear in both the middle and late stages of pregnancy.9PubMed Central. Loss of Slc38a4 imprinting is a major cause of mouse placenta hyperplasia in somatic cell nuclear transferred embryos at late gestation In cloned cattle, the picture is similarly grim. Researchers tracking SCNT bovine pregnancies over a decade found that abortion rates were highest between 150 and 200 days of gestation, with fetuses often oversized and placentas showing enlarged umbilical cords and abnormal tissue growth.10Scientific Reports. Transcriptome-wide analysis of the SCNT bovine abnormal placenta during mid- to late gestation The underlying cause is misregulation of imprinted genes that normally keep placental growth in check.11PubMed. Abnormal expression of the imprinted gene Phlda2 in cloned bovine placenta
These are not abstract laboratory curiosities. In commercial animal cloning, where teams have strong economic incentives and decades of practice, cloning efficiency for cattle still sits around 6 to 15%, defined as the number of live offspring born per embryo transferred. For pigs, it hovers around 6%. A meaningful portion of those live-born clones suffer health problems in the weeks after birth, and some surrogate mothers develop complications from abnormal pregnancies.12PubMed Central. Update on the state of play of Animal Health and Welfare and Environmental Impact of Animals derived from SCNT Cloning and their Offspring, and Food Safety of Products Obtained from those Animals Translating those odds to a human context, where the ethical stakes are incomparably higher and the tolerance for failed pregnancies is essentially zero, makes clear why no credible scientist has proposed attempting it.
Therapeutic Cloning Versus Reproductive Cloning
Much of the confusion around human cloning stems from two radically different goals sharing the same underlying technique. Therapeutic cloning creates a line of embryonic stem cells genetically matched to a patient. Reproductive cloning creates a new organism.13Nature Reports Stem Cells. What’s the difference between cloning embryonic stem cells and cloning a new organism? Both start with SCNT, but therapeutic cloning stops at the blastocyst stage, roughly a hollow ball of around 100 cells, and never involves a pregnancy. The potential medical value lies in producing stem cells that could replace damaged tissues without triggering immune rejection, since the cells carry the patient’s own DNA.
In practice, however, therapeutic cloning via SCNT has remained expensive and inefficient even after Mitalipov’s breakthrough. A competing technology, induced pluripotent stem cells (iPSCs), can achieve something similar without requiring human eggs at all. A patient’s skin or blood cells are chemically reprogrammed into stem cells directly. Some researchers have argued that SCNT-derived stem cells may offer more thorough reprogramming of the cell’s epigenetic memory, potentially making them behave more like “true” embryonic stem cells.14Cell Stem Cell. Nuclear Transfer Dilemma: SCNT vs. iPSCs in Personalized Medicine But the practical advantages of iPSCs, which do not require egg donors or complex microsurgery, have made them the dominant approach for personalized stem cell therapies.15PubMed Central. A highly efficient method for generation of therapeutic quality human pluripotent stem cells by using naive induced pluripotent stem cells nucleus for nuclear transfer
The Legal Landscape Is Nearly Unanimous
Virtually every country that has addressed the question has banned human reproductive cloning. In 2005, the United Nations General Assembly approved a non-binding declaration calling on member states to prohibit all forms of human cloning as incompatible with human dignity, passing by 71 votes to 35 with 43 abstentions.16PubMed Central. UN committee approves declaration on human cloning The abstentions and the non-binding character of the declaration hint at the real complexity: countries disagree sharply on whether to ban only reproductive cloning or therapeutic cloning as well. No two countries have adopted identical regulatory frameworks, and the legal position in many places remains unsettled or deliberately vague.17PubMed Central. Variations and voids: the regulation of human cloning around the world
In practice, the countries with the most advanced biotechnology sectors tend to explicitly ban reproductive cloning while permitting some forms of therapeutic research. The United Kingdom, for example, allows licensed SCNT for research purposes. The United States has no federal law banning human cloning, but the FDA has asserted authority over any attempt to clone a human, and several states have their own bans. China prohibits reproductive cloning while supporting therapeutic research. The patchwork means that in theory, someone could attempt human cloning in a jurisdiction with weak or absent regulation, but the biological barriers described above make this a hypothetical threat rather than a realistic one.
Could iPSCs or Other Technologies Be Used Instead?
SCNT is not the only conceivable route to a cloned human. In 2009, three independent research teams produced live mice entirely from induced pluripotent stem cells using a technique called tetraploid complementation. The process works by fusing two early embryonic cells to create a tetraploid embryo (one with a doubled chromosome set), then injecting iPSCs into it. The tetraploid cells form the placenta, while the iPSCs develop into the fetus. The resulting mouse is genetically identical to the iPSC donor, making it a clone produced without any nuclear transfer at all.18Cell Stem Cell. Cloning Mice and Men: Prohibiting the Use of iPS Cells for Human Reproductive Cloning
In theory, the same technique could work in humans: inject human iPSCs into a human tetraploid blastocyst to produce a child who is a clone of the iPSC donor. In practice, this has never been attempted, and ethicists have called for existing anti-cloning laws to be updated to cover iPSC-based methods as well as SCNT.19PubMed Central. Cloning mice and men: prohibiting the use of iPS cells for human reproductive cloning The biological obstacles are at least as daunting as those for SCNT-based cloning, and in some respects worse, since tetraploid complementation has never been demonstrated in any primate species.
Blastoids and Synthetic Embryo Models
A separate line of research has produced structures that resemble very early human embryos but were made entirely from stem cells, without sperm, egg, or cloning. These structures, called blastoids, mimic the blastocyst stage of development and can be generated at high efficiency. Researchers have produced human blastoids that develop the correct cell types in the right proportions and even simulate early implantation behavior when exposed to uterine-like conditions in a dish.20Nature. Human blastoids model blastocyst development and implantation They can be generated in essentially unlimited numbers, making them powerful tools for studying the earliest stages of human development.21Nature Protocols. Generating human blastoids modeling blastocyst-stage embryos and implantation
Blastoids are not clones. They are not really embryos in the traditional sense either, since they are assembled from stem cells rather than arising from fertilization or nuclear transfer. But they raise some of the same philosophical and legal questions. Current laws governing embryo research tend to define an embryo by how it was made, such as through fertilization, cloning, or parthenogenesis. Structures built from stem cells that look and behave like embryos but do not fit any of those categories expose gaps in existing legal frameworks.22PubMed. Simulating Life, Challenging the Law: Creation and Responsibility in the Governance of Human Embryo Models As these models become more sophisticated, deciding what counts as an embryo, and what protections apply, becomes an increasingly urgent question.
The Ethics Question Nobody Has Resolved
Even if every technical hurdle were cleared tomorrow, human reproductive cloning would still face an ethical gauntlet that no scientific advance can bypass. The core dilemma pits two rights against each other: a potential parent’s right to reproductive freedom and a cloned child’s right to self-determination. Proponents of reproductive cloning do not generally deny that it could cause psychological harm to the resulting person; the disagreement is over whether that potential harm outweighs reproductive autonomy.23PubMed. Human reproductive cloning: a conflict of liberties
A cloned child would share their entire nuclear genome with a living (or previously living) person. That raises questions about identity, expectations, and the psychological burden of being a genetic copy of someone whose life trajectory is already known. These are not mere thought experiments. They are real concerns that have persuaded bioethicists across a wide ideological spectrum to oppose reproductive cloning even when they support other controversial reproductive technologies.
The debate has also been shaped by how the media frames cloning stories. Research analyzing over 5,000 news articles about therapeutic cloning found a persistent dialectic of hope and fear in both American and British press coverage, with sensationalism driven largely by the economic pressures of newsrooms rather than by the science itself.24Journalism & Mass Communication Quarterly. Scientific Sensationalism in American and British Press Coverage of Therapeutic Cloning Public perception of cloning has been influenced as much by science fiction and breathless headlines as by anything that has actually happened in a laboratory.
In Vitro Gametogenesis and the Shifting Frontier
While traditional cloning research has stalled at the reproductive threshold, a related technology is quietly reshaping conversations about who can become a biological parent. In vitro gametogenesis, or IVG, aims to create functional eggs and sperm from ordinary body cells. If it works in humans, it could allow same-sex couples to have children who are biologically related to both parents, or let a single person produce both egg and sperm from their own cells.25PubMed Central. Considerations for the future of in vitro gametogenesis in fertility care IVG does not produce a genetic clone, since the resulting child’s genome would be a new combination of parental DNA, like any naturally conceived child. But it shares with cloning the capacity to upend assumptions about biological parenthood, and it faces some of the same regulatory uncertainties. As synthetic embryology, blastoid research, and IVG converge, the boundaries that once clearly separated “cloning” from “assisted reproduction” from “embryo modeling” are blurring in ways that existing laws and ethical frameworks were not designed to handle.