Sex is not necessary for all members of the animal kingdom. Of course it has its advantages, primarily, combining genetic material adds to the diversity of a species and makes it more ‘hardy’. But in vertebrates, organisms that are considered ‘more complex’ (ie. fish, amphibians, reptiles, birds and mammals) asexual reproductions is extremely rare and is thought to be limited because of the complexity of vertebrate genetics and body plans.
Recent discoveries has defied this logic however. A captive female hammerhead shark had a ‘virgin’ birth. The shark, which lives at Henry Doorly Zoo in Nebraska gave birth to a pup despite having had no contact with a male. A similar incidence was reported of a komodo dragon in Chester Zoo in the UK.
Originally it was thought that the females were storing sperm from a previous encounter for an extended length of time but genetic tests have now confirmed that the offspring share their DNA with only individual, their mother. This type of reproduction is known as parthenogenesis and it not entirely clear how or why it developed. One theory suggests that it evolved as a mechanism to deal with times of isolation. For example, if a komodo dragon found itself on an island without a mate, a few offspring could be produced while it waited for another komodo dragon to arrive and the population could be sustained until a viable breeding pool arrived.
This new ‘twist’ has created many questions including what other animals are capable of reproducing in this fashion. So far the ability has not been documented in mammals and birds but it has only been with the recent advent of genetic testing that such unusual cases can be investigated.