Lizard gives birth without mating as parthenogenesis draws attention to human reproduction questions

A female lizard at Exotic Zoo in Telford, Shropshire, gave birth to eight hatchlings without any contact with a male, in what scientists describe as parthenogenesis, a natural form of asexual reproduction.

Staff said the hatchlings are genetically identical clones of their mother, Carol the casque-headed iguana, who appears to have laid eggs and produced offspring without mating.

Parthenogenesis is documented in a wide range of animals, including sharks, snakes, crocodiles, crustaceans, scorpions and wasps. In many species, it arises when a female has been isolated and lacks access to a mate, allowing eggs to develop into embryos without fertilization by sperm. Offspring produced this way are typically female and genetically similar to the mother.

The recent case has reignited discussion about parthenogenesis in mammals and, in theory, its possibility in humans. Historically, scientists believed parthenogenesis was either rare or impossible in mammals, but more recent experiments have challenged that assumption.

In 2022, Chinese researchers reported achieving parthenogenesis in mice using a gene-editing technique known as CRISPR. One live mouse born through parthenogenesis survived to adulthood and even reproduced, illustrating that the mechanism can, under specific circumstances, produce viable offspring in mammals. Still, researchers emphasize that this remains a highly controlled, experimental scenario and not something approaching natural human reproduction.

Dr. Louise Gentle, a lecturer in zoology at Nottingham Trent University, cautioned that parthenogenesis in humans is technically possible but would require a highly unlikely constellation of genetic changes. 'There have been some studies in laboratories that have produced parthenogenic embryos in mammals, but these have involved genetic modification,' she told the Daily Mail. 'Although our DNA is modified through natural processes such as mutations, the chances of modifications that lead to parthenogenesis are rare. To get parthenogenesis in humans, you would need to have individuals with the same chance mutations (there would have to be many mutations) breeding together. It’s an extremely long shot, with a tiny probability, but it is technically possible.'

Tiago Campos Pereira, a professor of genetics at the University of São Paulo in Brazil, said there are 'biological barriers' established by our genetic makeup that prevents parthenogenesis in humans. But he noted those barriers might be altered by natural mutations. 'If a woman happened to have all those specific mutations by chance, perhaps she could have a virgin birth,' he told the Daily Mail.

Herman Wijnen, a professor of biological sciences at the University of Southampton, said mice are the only mammal species where parthenogenesis has been successfully attempted. 'I don’t think that anyone is pursuing this in humans due to obvious ethical concerns,' he told the outlet.

Researchers emphasize that, in humans, eggs rely on epigenetic cues from the sperm to begin development. Epigenetic modification involves changes in gene activity without altering the DNA sequence itself—often likened to highlighting text to change how a message is read. 'The 'highlighting' that comes from the sperm is essentially what instructs the egg to develop,' Dr. Gentle explained.

While CRISPR-based editing could, in theory, induce similar changes, performing such work in humans raises profound ethical questions and is widely condemned as illegal and unethical in many jurisdictions. Even if the barriers could be bypassed, experts warn that a human population derived from parthenogenesis would face serious genetic diversity risks.

Experts note that parthenogenesis could serve as a survival strategy for some species in the short term, but relying on a single-parent mode of reproduction would reduce genetic diversity and increase vulnerability to disease. Dr. Gentle warned that if a population were founded entirely by parthenogenetic lines, a single pathogen could threaten the entire group. 'Parthenogenesis is risky in terms of species survival because if one individual is susceptible to disease, all individuals would also be susceptible, causing the population to go extinct,' she said.

The current lizard case underscores how quickly reproductive biology can surprise researchers and the public. It also highlights a broader, ongoing debate about how far scientists should push genetic techniques and what implications those advances may have for human reproduction.

Observers stress that the warm reception for scientific advances should not be conflated with imminence of human virgin births. The biology that enables parthenogenesis in some species does not mean it is readily transferable to humans, and ethical and legal frameworks remain central to any discussion about attempting such work in people. Nevertheless, the possibility—however remote—continues to invite questions about the specialized roles of the sexes in reproduction and the boundaries of genetic manipulation in medicine and biology.