The resulting offspring therefore is doubly genetically disadvantaged.
"It had no father to provide genetic diversity, and it even lacks its mother’s full genetic makeup," Shivji said.
He speculates that such births can only occur when females do not have access to males, such as in a captive setting, or in the wild when overfishing depletes shark populations.
"We now are concerned, because if conditions prompt asexual reproduction in the wild, the species could be at an evolutionary disadvantage," he said.
While the new research, published in today’s Royal Society Biology Letters, represents a rare, documented case of an asexual birth in a shark, it's already known that certain birds, reptiles and amphibians also possess the ability.
Shivji said it is significant that sharks can now be added to the list, since they are the world’s oldest living vertebrates, a group of backboned animals that also includes humans.
Since humans and mammals lack the ability, he suspects it evolved early on in the vertebrate lineage, but was lost in some groups when they diverged from their common ancestor with sharks about 450 million years ago.
