Several hypotheses have been put forward over the years, with the most popular suggesting that they made the 8,000-kilometre journey across the ocean on a mat of vegetation or debris. However, according to Brice Noonan of the University of Mississippi and Jack Sites of Brigham Young University in Utah, the answer is much simpler: they walked there.

Fiji and Tonga were once part of the ancient super continent of Gondwana, as were the Americas. Noonan and Sites speculated that the Pacific iguanas may have migrated to the islands during this period, which would mean that they would have to be millions of years old. Sure enough, when they used a ‘molecular clock’ analysis of the island species’ DNA, they found that they have been around for more than 60 million years, well before the eventual breakup of Gondwana.

But why aren’t iguanas found on other Pacific islands? According to Noonan and Sites, fossil evidence suggests that they were once distributed more widely, but that the other populations went extinct at around the same time as humans colonised those islands.

March 2010