"We thought it was a very long shot but that we ought to check it out," London Zoo's Gibson said. "We were able to rule out sexual reproduction completely."
In parthenogenesis, an unfertilized egg develops into an embryo using its two sets of maternal chromosomes.
The unusual process is most commonly known in smaller invertebrates, such as aphids and zooplankton. But it is occasionally recorded in much larger animals, including some reptiles and amphibians.
The main drawback to this mode of reproduction is that populations can become genetically very similar, making them more vulnerable to disease and less able to adapt to change, such as altered climate conditions or new predators.
But there may have been an important advantage to Komodo dragons having fatherless young, the study team says.
The reptiles are native to islands in Indonesia, where female castaways could have need to start new colonies on their own, the researchers say.
"If a female gets swept off her desert island to a new desert island where there are no other dragons, then she can reproduce parthenogenetically," Gibson said.
The offspring of such virgin births are all male, because of the genetics involved in self-fertilization in lizards, Gibson explained.
"When the offspring reach sexual maturity, the mother can reproduce with her own sons, and you're back to a sexually reproducing population," Gibson said.
Parthenogenesis has been found in a number of other unexpected animals in recent years, he added.
"It was recorded in a python a couple of years ago," he said. "Turkeys can do it, and it's also happened in fish."
Previous suspected cases of virgin births in zoo animals include a white spotted bamboo shark at the Belle Isle Aquarium in Detroit.
(Read "Shark Gives 'Virgin Birth' in Detroit" [September 25, 2002].)
When the female shark laid a clutch of eggs in 2002, six years after her last contact with a male, aquarium staff assumed they were infertile. Yet the eggs later hatched.
Gibson says such cases raise the question of whether this phenomenon is happening in wild animals as well as those in captivity.
But he thinks it unlikely that parthenogenesis can shed any light on how the Virgin Mary gave birth in a manger.
"I'm not aware of it in a mammal species," he said, "So if you're looking for support for the theory of the Virgin Birth, then I think it's a bit of a long shot."
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