At the Water's Edge: Macroevolution and the Transformation of Life

One of the hallmarks of life is change. In his first book, Zimmer, a senior editor and feature writer at Discover magazine, has chosen to explicate two of the biggest examples of organic evolution the Earth has ever seen. He starts by describing how fish, beginning between 350 and 400 million years ago, evolved into creatures who crawled out of the water and, eventually, into terrestrial mammals able to breathe air, withstand the pressures of gravity and move about without the aid of water. He then turns his attention to how, 40-50 million years ago, some well-adapted terrestrial mammals went back into the sea and, over time, gave rise to whales, porpoises and their marine relatives. Zimmer shows that the transformation back to aquatic life--without the luxury of gills, fins and the host of additional adaptations that make fish so successful--was an amazing evolutionary feat. Zimmer treats the controversy surrounding the mechanism of macroevolution only cursorily: he opts not to take a position in the conflict between the proponents of punctuated equilibrium and the advocates of gradualism. But he makes up for that lack with his gripping account of how scientists work. By accompanying scientists into the field, visiting them in their laboratories and conducting extensive interviews with them, Zimmer communicates the excitement of cutting-edge scientific research and fieldwork. More than just an informative book about macroevolution itself, this is an entertaining history of ideas written with literary flair and technical rigor. Line drawings and diagrams throughout. (Apr.)