Cloning never disappeared, but it took a very different path than most people expected in the late 1990s. After Dolly the sheep made worldwide headlines in 1996, the public imagined a future of copied humans and identical armies. Instead, cloning ran headfirst into biological barriers that proved far harder to overcome than anyone anticipated. Today, cloning technology is quietly at work in pet reproduction, livestock breeding, wildlife conservation, and ambitious de-extinction projects, while human cloning remains banned in over 30 countries and has never been successfully attempted.
Why the Early Excitement Faded
Dolly the sheep was the proof of concept that a mammal could be cloned from an adult cell. But Dolly also became the first warning sign. By age five and a half, she developed arthritis in her left hind leg, a condition that typically doesn’t appear in sheep until around age 10. The joints affected, her rear hip and knee, were unusual locations for sheep arthritis, which normally strikes the forelegs. Researchers had suspected since 1999 that Dolly might be aging prematurely after discovering her telomeres, the protective caps on chromosomes that shorten with age, were about 20% shorter than expected for a sheep her age. She was euthanized at six due to progressive lung disease.
Dolly’s problems weren’t a fluke. They reflected a fundamental issue with how cloning works at the molecular level. The process, called somatic cell nuclear transfer, involves taking the DNA from an adult cell and inserting it into an egg that’s had its own DNA removed. The egg then has to “reboot” that adult DNA back to an embryonic state. That reboot is almost always incomplete. Researchers at Harvard Medical School identified 222 regions of the genome that activate normally in IVF embryos but stay silent in cloned ones. Those genes are held in check by chemical tags, essentially locks on the DNA packaging that the cloning process fails to remove. Forty-nine of those locked genes are themselves responsible for turning on other genes, creating a cascade of failures.
The practical result: cloning efficiency in mice still hovers around 1 to 2 percent. In cows, it ranges from 5 to 20 percent. In most other species, it’s 1 to 5 percent. For comparison, standard IVF in mice succeeds about 50 percent of the time. Among the cloned embryos that do survive to later stages of pregnancy, many develop placental abnormalities, and a significant number die shortly after birth because their bodies can’t adapt to life outside the womb.
Human Cloning: Universally Off the Table
No one has ever cloned a human being, and the legal landscape makes it extraordinarily unlikely. Over 30 countries, including France, Germany, and Russia, have outright bans on human cloning. In 2005, the United Nations General Assembly adopted a declaration calling on all member states to prohibit human cloning as incompatible with human dignity. The Council of Europe’s 1997 Convention on Human Rights with Regard to Biomedicine explicitly prohibits “any intervention seeking to create a human being genetically identical to another human being, whether living or dead.” The European Union funds embryonic stem cell research where national laws allow it but has banned funding for human cloning.
Beyond the legal barriers, the biological ones are just as daunting. When Chinese researchers cloned the first primates in 2018, two macaque monkeys named Zhong Zhong and Hua Hua, only embryos made from fetal cells survived. Those created from adult cells died shortly after birth. Given that cloning success rates in primates are even lower than in other mammals, and that the health complications remain unpredictable, no credible scientific institution has pursued human reproductive cloning.
Stem Cell Science Took a Different Route
One of the original promises of cloning was therapeutic: the idea that you could create cloned embryos to harvest perfectly matched stem cells for regenerative medicine. That vision was largely overtaken in 2006 when researchers discovered they could reprogram adult cells directly into stem cells without cloning at all. These induced pluripotent stem cells can be generated in bulk from a simple skin or blood sample. Newer methods produce these cells without permanently altering the patient’s DNA, which reduces the risk of genetic problems. This technology effectively removed the main medical justification for human cloning research, and most labs pivoted accordingly.
Where Cloning Is Actually Thriving
The biggest commercial success story for cloning is surprisingly mundane: copying pets. ViaGen Pets and Equine, the only pet cloning company in the United States, charges $50,000 to clone a dog or cat and currently has a five to seven month waitlist. The company has cloned over two thousand animals in its 25-year history. The process works the same way as any other cloning: a tissue sample is preserved from the original animal, and the DNA is transferred into a donor egg. The resulting puppy or kitten is a genetic twin of the original, though personality and markings can vary since those are shaped partly by environment and random developmental processes.
In agriculture, the FDA concluded in 2008 that meat and milk from cloned cows, pigs, and goats, along with the offspring of any cloned animals, are as safe as conventionally produced food. Cloning in livestock is used primarily to replicate animals with exceptional genetics for breeding purposes rather than to produce food directly. The clones themselves are expensive to create, so they typically become breeding stock whose offspring enter the food supply through normal reproduction.
Conservation Cloning Is Producing Results
Perhaps the most compelling current use of cloning is in saving endangered species. In 2020, a black-footed ferret named Elizabeth Ann became the first cloned U.S. endangered species. She was created using preserved tissue from a ferret named Willa, who lived in the 1980s. The effort has since expanded significantly. In 2023, two more ferrets, Antonia and Noreen, were cloned from Willa’s tissue. By 2024, the program hit a critical milestone: Antonia’s offspring successfully reproduced naturally, producing four litters totaling 12 kits (6 females and 6 males) at the Smithsonian’s National Zoo and the National Black-footed Ferret Conservation Center.
This matters because all living black-footed ferrets descend from just seven individuals, leaving the species dangerously inbred. Cloning ferrets from decades-old tissue reintroduces genetic diversity that no longer exists in the living population. Elizabeth Ann and Noreen have both since died, but their genetic legacy continues through the next generation. The U.S. Fish and Wildlife Service is clear that cloning isn’t a replacement for habitat protection and traditional conservation, but it adds a tool that didn’t exist before.
De-extinction: The Boldest Bet
The most ambitious cloning-adjacent project underway is Colossal Biosciences’ effort to create a cold-adapted elephant with the key biological traits of a woolly mammoth. The company isn’t cloning a mammoth in the traditional sense, since no intact mammoth cells exist. Instead, they’re using CRISPR gene editing to modify Asian elephant DNA, which shares 99.6% similarity with the woolly mammoth genome. The goal is to edit roughly 65 genes responsible for cold-weather adaptations like dense hair, smaller ears, and subcutaneous fat layers, then use nuclear transfer to create embryos implanted in elephant surrogates.
The timeline is long. Elephant gestation alone takes 22 months, and the technical challenges of harvesting elephant eggs and maintaining surrogate pregnancies are enormous. Colossal frames the project around five goals, ranging from restoring Arctic grassland ecosystems to advancing multiplex genome editing techniques that could benefit conservation of living species. Whether or not a mammoth-like calf is ever born, the gene-editing tools being developed for the project are already being applied to endangered species work.
Why Cloning Stayed Niche
The short answer to “what happened to cloning” is that biology imposed limits the initial hype didn’t account for. The incomplete reprogramming problem, where cloned embryos fail to properly activate hundreds of critical genes, has proven stubbornly resistant to solutions. Success rates remain low across species, and health complications in cloned animals, while less dramatic than Dolly’s case suggested, are still more common than in naturally conceived ones. The technology works well enough for high-value applications where inefficiency is tolerable: a $50,000 pet, a prize breeding bull, or a last-ditch effort to save a species. But it never became the routine, reliable tool that 1990s headlines imagined. Instead, cloning settled into a handful of specialized roles where nothing else can do the job.