Virgin births move from animals to humans, experts say

Virgin births, known scientifically as parthenogenesis, occur when a female's unfertilised egg develops into an embryo. In a recent case at a zoo near Birmingham, a female casque-headed iguana laid eggs and produced eight hatchlings without any male involvement. Staff at Exotic Zoo in Telford, Shropshire described the long-term resident, Carol, as giving birth after simply laying eggs. The hatchlings were reported to be genetically identical to their mother.

Parthenogenesis is found in a wide range of animals, from sharks and snakes to crocodiles, crustaceans, scorpions and wasps. In those species, the offspring are not exact genetic clones of the mother; they are genetically similar and are always female. The process usually arises when a female isolates herself from potential mates, leaving reproduction to occur without fertilization.

The phenomenon, though rare, has challenged long-standing assumptions that mammals reproduce only through sexual means. Although parthenogenesis is observed across many animal groups, its appearance in mammals has remained controversial and limited. In 2022, researchers in China reported that parthenogenesis had been achieved in mice using a gene-editing technique called CRISPR, producing a live mouse born without fertilization that survived to adulthood and could reproduce. That finding, while limited to a laboratory setting, underscored how genetic manipulation can, in principle, enable parthenogenetic development in mammals, though it did not translate into a natural or readily replicable human event.

Experts note that, in nature, parthenogenesis typically becomes a viable option when a female has little chance of finding a mate. In the animal kingdom, this strategy can help sustain a population in the absence of males, but it also carries caveats. Offspring produced via parthenogenesis are generally not perfect copies of the mother; they share much of her genetic material but may carry variations that can affect fitness. In many species, such offspring are female, and the lack of paternal genetic contribution can limit genetic diversity over time, potentially increasing vulnerability to disease or changing adaptation dynamics.

Under current human biology, eggs require cues from sperm to initiate development, a signal process known as epigenetic modification that can be described as highlighting certain genes for expression. Some scientists say that, in theory, specific genetic changes could mimic these cues, allowing parthenogenesis to proceed in humans. But such modification would involve complex and coordinated mutations, and the ethical framework surrounding human gene editing would pose major barriers. Dr. Louise Gentle, a zoology lecturer at Nottingham Trent University, said parthenogenesis in humans is technically possible but would require unlikely, multiple genetic tweaks to occur in individuals who would need to mate in ways that could produce a birth. '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.'

Biologists also emphasize that there are biological barriers in humans that would have to be overcome. Tiago Campos Pereira, a professor of genetics at the University of São Paulo, said there are inherent limits set by human genetics that prevent parthenogenesis, although those barriers could theoretically 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. In practice, though, such an outcome remains highly speculative and ethically fraught.

Beyond the theoretical debates, real-world examples continue to emerge in other species. In recent years, researchers have noted incidents such as Yoko, a swell shark born to a mother in an all-female tank at a Louisiana aquarium, and other all-female lineages in various species. In Portsmouth, a 13-year-old snake named Ronaldo reportedly gave birth without mating, surprising students and staff who had assumed the snake was male. Such cases illustrate that parthenogenesis can occur in nature, sometimes spontaneously under specific ecological or social conditions.

Scientists warn that, even where parthenogenesis occurs, the long-term consequences for a population are complex. Because the offspring are genetically similar to the mother, widespread parthenogenesis could reduce genetic diversity and limit a species' ability to adapt to new diseases or environmental changes. '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,' Gentle said. While parthenogenesis is not ruled out in humans, experts widely regard it as unlikely to be a practical or desirable route for human reproduction, given ethical concerns and the potential for unintended consequences.

Overall, scientists describe parthenogenesis as a natural but infrequent strategy that can serve as a survival mechanism in some species. In humans, the established science points to a distant, heavily regulated possibility at best—one that confronts profound ethical and safety questions. As research continues in animal models and gene-editing technology evolves, the public should expect careful, case-by-case evaluation of any claims about human parthenogenesis, rather than any extrapolation from animal cases to real-world human reproduction.