Last year the discovery of a tiny fossilised jawbone hit the headlines. The jawbone, only a few centimetres long, and with 7 rows of teeth, had been found lying abandoned in a dusty museum where it had lain unnoticed for decades. It's rediscovery has caused a sensation in the world of palaeontology because scientists now believe it may be a tiny remnant of a "missing link", an ancient extinct animal that could provide a vital clue in our understanding of one of the great mysteries of science - how, 360 million years ago, a slimy fish-like creature grew legs and walked out of the sea, onto the land, and became our ancestor. This mystery, of how and why, long ago, we grew legs and crawled out of the water, has taken scientists a century to unravel. And this tiny jawbone may be a final clue.