An extinct Galapagos tortoise species could walk again, scientists believe.

Writing in Proceedings of the National Academy of Sciences, researchers report finding relatives of Geochelone elephantopus alive and well.

Cross-breeding these living tortoises might re-create the extinct species - though it could take a century.

The distribution of related tortoises between the islands was one of the pieces of evidence Charles Darwin used in formulating his theory of evolution.

But of 15 known Galapagos species, four have since gone extinct - elephantopus less than two decades after Darwin visited the island.