What Is Human Cloning?

A working definition

In biology, a clone is an organism, cell, or DNA sequence that is genetically identical to another. The word covers everything from a strawberry plant that has been propagated by cuttings to a strand of DNA copied inside a laboratory tube. When people say human cloning, they usually mean something far more specific and dramatic than the science actually does — typically the idea of creating a genetically identical person.

That gap between everyday language and scientific usage is the reason cloning is so widely misunderstood. The same word is doing several different jobs at once. To talk about it carefully, we have to pull those jobs apart.

Three kinds of cloning, not one

Scientists generally distinguish three categories of cloning. They share a name and a basic idea — producing something genetically identical to something else — but they are otherwise very different in technique, purpose, legality and ethics.

1. Gene (or molecular) cloning

This is the most common, routine, and least controversial kind. Researchers copy a specific stretch of DNA — a gene or fragment — inside a laboratory dish, usually by inserting it into a bacterial cell that will replicate it. Gene cloning underlies much of modern biology, biotechnology, and pharmaceutical development. It does not involve embryos and does not produce a clone of a person.

2. Therapeutic cloning

Here the goal is research, not reproduction. Scientists use a technique called somatic cell nuclear transfer (SCNT) to produce early-stage cells that can be studied in the lab. The intention is to learn about disease, develop potential cell-based therapies, or model how cells behave in regenerative medicine. Therapeutic cloning is heavily regulated and is permitted under strict conditions in some jurisdictions and prohibited in others.

3. Reproductive cloning

This is the meaning that captures the public imagination: producing a living organism that is genetically identical to an existing one. In animals, reproductive cloning has been demonstrated since the 1990s. In humans, it has not been done. It is broadly prohibited by national laws and international declarations, and the leading scientific and medical bodies consider it unsafe and ethically unacceptable.

How somatic cell nuclear transfer works, in plain language

Both therapeutic and reproductive cloning rely on a technique called somatic cell nuclear transfer, or SCNT. The high-level idea is straightforward, even though the practice is anything but.

Every cell in your body except the egg and sperm carries a full set of your DNA. SCNT exploits that fact. Researchers take the nucleus — the part of the cell that contains the DNA — from a body cell, and they place it inside an egg cell that has had its own nucleus removed. The reconstructed cell can then begin to divide, producing an early-stage embryo whose DNA closely matches the donor of the body cell.

What happens to that early embryo is the point at which therapeutic and reproductive cloning part ways. In therapeutic cloning, the cells are studied in the lab. In the (still hypothetical) human reproductive case, the embryo would be transferred to a uterus with the aim of producing a pregnancy.

We deliberately keep this explanation at a high level. This site does not publish laboratory protocols.

For a more detailed conceptual treatment see our explainer on somatic cell nuclear transfer and the comparison piece therapeutic vs reproductive cloning.

Has a human ever been cloned?

No verified case of a cloned human being exists. There have been claims over the years, including from groups promising imminent human clones, that have not been supported by independent evidence. The leading peer-reviewed literature, national academies and international health authorities treat reproductive human cloning as something that has not been accomplished, that would face severe safety risks based on animal data, and that is broadly prohibited.

In 2013, researchers reported producing human embryonic stem-cell lines using SCNT. That was a research result, not a step toward producing a baby. It mattered because it confirmed that the technique was possible in human cells, but the cells were studied in the lab and were not implanted.

Why the topic is controversial

Even if reproductive cloning were technically feasible — and there is no consensus that it currently is in humans — the ethical, legal, and social objections are substantial. The most consistently raised concerns include:

• Safety. Animal cloning has produced high rates of miscarriage, developmental abnormalities, and shortened lifespans in the resulting animals. Extending those risks to a human would be unacceptable to almost every medical ethics framework.
• Consent and identity. A future person cannot consent to the conditions of their own creation. Reproductive cloning would introduce a deliberately chosen genetic similarity in a way that ordinary reproduction does not.
• Dignity. International declarations frame reproductive cloning as a question of human dignity, not only of safety — a person should not be designed to be a copy.
• Family and legal status. Cloning blurs ordinary categories of parent, sibling, and donor in ways that family and inheritance law have not resolved.
• Equity and access. Powerful reproductive technologies historically concentrate among the wealthy. That alone raises fairness concerns.

Therapeutic cloning has its own debates, often centred on the moral status of early embryos. Different jurisdictions have arrived at different answers.

Where the field is now

In practice, much of the regenerative-medicine work that once depended on SCNT has shifted toward induced pluripotent stem cells (iPSCs) — ordinary adult cells that have been reprogrammed in the lab into a more flexible state. iPSCs do not require an embryo and are easier to work with, which is why most of the most-cited stem-cell research of the past fifteen years uses them.

Animal cloning continues for research purposes, particularly in agriculture and biomedicine, but is not mainstream. Reproductive human cloning remains widely prohibited and is not a credible near-term prospect in the scientific literature.

Further reading

• Types of cloning compared
• Therapeutic cloning
• Reproductive cloning
• Is human cloning legal?
• Glossary of cloning terms

Source standards. This explainer is based on widely accepted accounts of cloning biology and policy from the U.S. National Institutes of Health (NIH), the National Human Genome Research Institute (NHGRI), the World Health Organization (WHO), UNESCO declarations on the human genome and human cloning, and peer-reviewed literature in mammalian developmental biology.