Newspaper article The Christian Science Monitor

Best Recipe for Primordial Soup ; Back When Whales Walked on Land and Apes Swam in the Water

Newspaper article The Christian Science Monitor

Best Recipe for Primordial Soup ; Back When Whales Walked on Land and Apes Swam in the Water

Article excerpt

Richard Ellis's earlier books "Deep Atlantic" and "The Search for the Giant Squid" provided brilliant explorations of the ocean's depths and its mysterious life forms. His new book, "Aquagenesis," moves much further back in time. It's a dazzling tour de force that combines the deep insights of evolutionary biology, marine biology, and paleontology. Ellis traces the evolution of life in the sea from its earliest recorded appearance, dated by fossil evidence to about 565 million years ago, to the emergence of life from the sea about 55 million years ago.

The oldest fossils are simple animals shaped much like jellyfish or like annelids or worms, but the only characteristic that binds these fossils together is their symmetry. The most famous of these is Dickinsonia, which, in Ellis's words, "has the distinction of being the only fossil to be described as a jellyfish, a coral, a sea anemone, an annelid worm, an arthropod, a protozoan and a member of a new kingdom." These animals, who died out some 545 million years ago, were precursors to the greatest "evolutionary event in Earth's history: the Cambrian explosion."

The Cambrian seas were filled with "representatives of essentially all modern phyla." In these ancient waters, many marine invertebrates began to develop hard shells, passing along various forms and shapes to their descendants, such as the horseshoe crab and the nautilus.

Some of the largest marine invertebrates - the cephalopods, the order which includes octopi, squid, and cuttlefish - evolved during this period, eventually providing an important source of food for marine vertebrates.

According to Ellis, fish are one of the great evolutionary success stories: "Fishes have been swimming on Earth for more than 450 million years." They predated the dinosaurs by hundreds of millions of years, and they were the first creatures to have an internal skeleton. In that sense they are the ancestors of all vertebrates - amphibians, reptiles, birds, and mammals. Fishes are the most diverse of all vertebrates; more than 24,000 species inhabit the world's waters.

About 400 million years ago, aquatic vertebrates passed through a transitional stage from fishes to land reptiles. …

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