University of Tulsa researchers discovered virgin female cottonmouth and copperhead snakes giving birth, a process called parthenogenesis. This evolutionary rarity had previously been observed in captive female snakes, Komodo dragons, birds and sharks when they had no other option for reproduction, as there were no males available. But strangely, the cottonmouth and copperhead snakes had given birth as virgins even though there were plenty of healthy males around [source: Than].
Scientists don't know why the virgins forged ahead on their own. One theory is that the snakes, which were smaller than normal, had been scorned by the males and thus didn't have any other options. Another idea is that their parthenogenesis was simply a random biological error, or that the snakes had contracted some kind of bacteria or virus that triggered the blessed events [source: Than].
Parthenogenesis happens when a cell is produced along with the egg, and the cell acts like a sperm to fertilize the egg. The resulting offspring, then, are part-clone and part individual [source: Than].