Great white sharks in the Mediterranean may have first arrived from the seas around Australia about 450,000 years ago, genetic studies have suggested.
Researchers writing in Proceedings of the Royal Society B believe the arrival may have been simply a migratory wrong turn by a few pregnant females.
A tumultuous climate between ice ages may have been the cause.
The species - Carcharodon carcharias - would have remained in the Med because it returns to spawn where it was born.
It was previously assumed that the great whites in the Mediterranean were most closely related to their nearby cousins in the Atlantic Ocean.
But now, a team led by Les Noble of the University of Aberdeen has examined the several groups of sharks' mitochondrial DNA - genetic material passed through the maternal line that is particularly suited to tracing lineages.
The team found that the Mediterranean sharks were very different to the Atlantic group and more like sharks from Australia and New Zealand.
Although changes to the DNA in the different populations happen randomly, they do happen with a regular average rate.
As a result, the few differences between the Australian and Mediterranean sharks are an indication of how long ago they parted ways: 450,000 years ago - a time between ice ages that would have seen many effects of a changing climate.
That was a time of interglacials, when you would've had all kinds of changes in the currents going down the east and up the western coast of Africa, Dr Noble told BBC News.
The team hypothesises that strong, warm currents pushing the sharks northward would have put them far off course.
They might have gone a considerable way up there before the warmth ran out. Then they start trying to turn east and north and the first place you can go east, of course, is the Straits of Gibraltar.
It's not too much of a stretch to imagine the odd one might indeed do a 'wrong turn' and make this kind of migration.
Rest of article: http://www.bbc.co.uk/news/science-environment-11765412
