Genetic markers allowed Les Noble, a shark geneticist at the University of Aberdeen, to compare the Mediterranean sharks with the other populations.
"We were absolutely astonished. It was a moment of scientific serendipity. We looked at the DNA signature of the sharks and found they were all from the same extended family. The founding mothers had the same DNA as great white sharks found off the coast of Australia," Noble said in a press release.
The geography of the Mediterranean made it a shark trap. There was only a small entrance in at the Straits of Gibraltar, and plenty of peninsulas, islands, and channels to block navigation out. The scientists do not believe any more great white's are entering the Mediterranean now.
SEE ALSO: Is the Shark a Lonely Hunter?
"But because white shark females return to the area where they give birth, once they birth in the Mediterranean they become a fixture, shaping and rebalancing the ecosystem," said Cathy Jones, a shark geneticist from the University of Aberdeen in a press release.