Life on a Young Planet: The First Three Billion Years of Evolution on Earth [Illustrated] (Hardcover)

Knoll asserts the benchmark for comprehending how life may have started was the Urey-Miller experiments of the 1950s. By assuming a particular composition of Earth's early atmosphere and bombarding that recipe with electricity to duplicate lightning, Urey and Miller produced amino acids. Knoll credits these experiments not with showing how life began, but by their stimulation of much further research. Since then, geologists have revealed increasingly older rocks. Instead of buried deep beneath the surface as might be expected, they are often found well exposed. Knoll's expeditions to chilly Siberian sites are offset by the roaring desert of outback Australia. Both locations have provided researchers with new information on composition, chemical and environmental processes, and, most significantly, Precambrian fossils.

The many research fields now involved in developing a picture of life's beginnings indicate how complex a task unveiling "simple" can be. Early life, of course, was microscopic. Sometimes it isn't fossils that are found, but spoor remains - tracks once left in mud, images of forms, and, most intriguing for many, chemical signatures. The chemical, is usually carbon, that fundamental element of life. But other elements, iron, sulfur and oxygen also carry messages about living processes.

Knoll manages a delicate arabesque as he presents us with the evidence obtained and the interpretations derived from it. He carefully delineates the fossil information given by the rocks, mixing it with geological and geochemical processes. Various researchers are given voice through his narrative. Where issues are contentious, and most ideas of early life fit that description, he explains the reasons behind the stance, then offers his own choice. While the conflict is rarely solved, none of his solutions are arbitrary or based on personality. You are still left to satisfy your own mind through his references. Knoll's prose presents this information and discussion with clarity and balance. At the end, with these lucid explanations as background, he considers that answers to many of our questions may be found on our nearest planetary neighbour - Mars.

Beyond the informative text provided, Knoll enhances the book with site photographs to convey the scale of the locations excavated. Ancient landscapes are today stark, and the photos do little to convey the nippy Kotuikan cliffs or the roasting Precambrian site of North Pole, Western Australia. A collection of plates offers stunning colour images of ancient fossils and some modern equivalents. He further diagrams phylogenetic trees showing the relationship of organisms and why they are considered related. Not all life, he reminds us, has followed the path to complexity. With a good, but not exhaustive, reading list to examine, the reader may continue the pursuit. The younger reader may even wish to further the knowledge we have. Knoll exhorts the next generation of early life researchers to examine the questions and go afield to provide more answers. There are few worthier causes.