A female hammerhead shark gave birth to a pup in the Henry Doorly Zoo in Nebraska in 2001 despite having no contact with a male shark. Thanks to new DNA profiling technology, scientists have been able to show conclusively that the shark pup contained no genetic material from a male. Before you whip out your Book of Revelations and start begging for forgiveness, you should know that this is an example of a naturally occurring phenomenon called parthenogenesis. In parthenogenesis, egg cells develop as an embryo without the addition of any genetic material from a male sperm cell. This reproductive process has been witnessed in bony fish before, but never in cartilaginous fish like sharks.
Asexual reproduction decreases genetic diversity, and thus can weaken a species as a whole. Witnessing the hammerhead’s virgin birth is thus a cause of concern for scientists, worried about further weakening of already threatened shark species in the world.