"Pythons are an old, ancient species. We've seen this in more advanced species like garter snakes," said Booth, adding that the discovery helps scientists learn more about the snakes' evolutionary family tree.

It's still a mystery as to why parthenogenesis happens, though Booth hypothesizes that geographic isolation from males and captivity may have a lot to do with it.

In Thelma's case, her virgin birth may have been triggered by ideal living conditions, zoo curator McMahan speculates.