Why don't you look more like a hagfish? Scientists offer clues.

As the forces of natural selection led our aquatic ancestors wriggling into ever-shallower waterways and transformed their powerful fins into land-faring legs, most of the world was far too busy swimming to notice.

It was the Paleozoic Era's Devonian period, known as the Age of Fish, and these eccentric forays were occurring at the fringes of ocean society. In the meantime, the world's waterways were coming to be dominated by the beaky, often turtle-like, faces of the armored class of fish known as placoderms.

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