LONDON — It was a vast boat that saved two of each animal and a handful of humans from a catastrophic flood. But forget all those images of a long vessel with a pointy bow — the original Noah’s Ark, new research suggests, was round. A recently deciphered 4,000-year-old tablet from ancient Mesopotamia — modern-day Iraq — reveals striking new details about the roots of the Old Testament tale of Noah. It tells a similar story, complete with detailed instructions for building a giant round vessel known as a coracle — as well as the key instruction that animals should...