Scientists recently discovered the first two-headed shark embryo from an egg-laying species.

Anecdotal evidence suggests the number of two-headed sharks has been increasing since 2008, when a fisherman discovered a two-headed blue shark embryo in the Indian Ocean, according to NationalGeographic.com.

Scientists are having a hard time agreeing why this is happening. Some researchers, like marine scientist Nicolas Ehemann, blame overfishing, according to the Daily Mail.