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Cradled by the sea

Aquagenesis: The origin and evolution of life in the sea by Richard Ellis,
Viking/Penguin, $25.95, ISBN 0670030236

THEY鈥橰E an opinionated and pugnacious bunch, palaeontologists. Hardly
surprising, really. You need to be a bit of an obsessive to take on more than 3
billion years of evolution. Add in the phonetic mayhem of fossil names to sift,
and you have the ideal subject for Richard Ellis鈥攚riter, illustrator and,
his agent says, 鈥渇act junkie鈥�.

In Aquagenesis, Ellis turns to the sea to plot life鈥檚 evolutionary path from
those early Precambrian beginnings. He follows a slightly erratic path through
ideas and interpretations of the Precambrian Ediacaran organisms, the Burgess
Shale creatures and a few other invertebrate fossils.

Most of the book is devoted to the evolution of marine vertebrates, from fish
to mammals. I wished Ellis had used his considerable artistic talents to explore
the little-known and bizarre world of the extinct jawless fish as well. But he鈥檚
gripped by an unanswerable question. For Ellis, it鈥檚 鈥渢he most mysterious and
most spectacular鈥� of all evolutionary events. Why did some mammals, reptiles and
birds return to the sea?

Unfamiliar and interesting problems get a welcome airing before we are
plunged into the familiar muddy waters of the aquatic ape hypothesis. Ellis
gives a sympathetic hearing to the notion put forward by Alister Hardy and
Elaine Morgan鈥攖hat modern human physiology owes much to ancestral hominids
that lived half in, half out of water.