The Plausibility of Life-resolving Darwin’s dilemma, by Marc Kirschner and John Gerhart. Yale University Press, 2005. ISBN 0-300-10865-6. Reviewed by Louette McInnes.

This book was written for the general public with an interest in evolution, and also for people working in fields connected with evolutionary biology-geneticists, palaeontologists, biochemists, cell biologists, developmental biologists. In short, anyone who wants an overview and integrated picture would find something of interest. Language has been kept less technical, and explanations and glossary are more than sufficient.

The book at first almost appeared to be an ‘intelligent design’ ploy. That was partly from the name, facilitated variation, the authors give to their theory. Fortunately, the back flap tells who the authors are-Kirschner is chair of the Department of Systems Biology, Harvard, while John Gerhart is a graduate school professor at UC Berkeley. The real purpose of the book was to attempt to sort out the three main strands of Darwin’s theory-natural selection, inheritance, and variation. They felt variation was the main area being attacked by creation scientists and those proposing intelligent design.

For someone who is not a biologist but has tried to keep up with developments relating to evolution, the book was quite a revelation in terms of how much of biology is concerned with evolution or explaining variation. The cytoskeleton and how it forms, the ways that nerves form and interconnect, and the how, when and why of capillary formation-all this was made relevant to the ways in which a relatively small genetic change can produce major structural changes.

Hox genes, the major ‘switches’ that do things like turn on or off teeth in dinosaurs and birds, are explained; there is also a good bit of detail on how the embryo is segmented and why cells in certain areas develop in certain ways.

Some nice examples were given. Nerves were likened to an electrical outlet – you can plug any sort of equipment into the outlet and have it work. The outlet doesn’t care what is attached, it just delivers the signal. So the basic nerve cell, once it attaches an axon to a target, is really a multipurpose structure, giving the organism an opportunity for putting new types of sensors in place. The authors also showed how new, repaired or growing tissues induce the growth of new blood vessels-low oxygen causing the cells to put out a chemical that causes capillary cells to reproduce and migrate to those areas. This system allows a newly ‘enlarged’ strucure to develop the necessary blood supply without requiring a major change in the genes related to blood vessels.

The book isn’t always an easy read, but it certainly was a fascinating one.

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