"The Extended Phenotype" is the 4th and most demanding of Richard Dawkins' books that I've read. I hadn't realized that it was aimed mainly at his professional colleagues so was surprised at the amount of concentration, hard thinking and puzzled head scratching required to work through it. But what a glow of satisfaction: to finish such a challenging book, feeling that most of it has made sense to me. Like his other books (the ones I've read: "The Selfish Gene", "The Blind Watchmaker" and "Unweaving The Rainbow"), it's beautifully clearly written, with most of the more esoteric terms defined in the glossary at the back of the book. Not all of the terms could be found there however and nor were many of those to be found in an ordinary dictionary. The book is not so self-contained as those aimed at the more 'popular science' end of the market - the ones that you can read from cover to cover without reaching for a dictionary or other source of clarification. That's why I can only claim to have understood *most* rather than *all* of the book.
This book follows on from "The Selfish Gene" and in it, Dawkins argues that the phonotypic effects of genes do not stop at the limits of the organisms that carry them. He suggests, for example, that the phenotypic expression of beaver genes stretch right to the edges of the lakes formed by their dams and the genes of some parasites are expressed in their hosts. So a snail might behave in a manner that puts itself in harm's way because the fluke living inside it has, somehow, managed to modify the snail's behaviour for its own ends - say to continue its life cycle inside one of the snail's predators. That is to say, the snail's behaviour is maximizing the survival of fluke genes rather than snail genes. He puts it very succinctly: 'an animal's behaviour tends to maximize the survival of the genes "for" that behaviour, whether or not those genes happen to be in the body of the particular animal performing it.' There are plenty of other fascinating examples of this sort. There are chapters covering such intriguing areas as evolutionary 'arms races', 'outlaw' genes and 'jumping' genes. Good use is made of thought experiments to help to figure out how and why certain adaptations might have evolved. 'Outlaw' genes for instance, might try to cheat the system to get themselves replicated more than their alleles, so how can the rest of the genome fight back? I particularly liked the idea of the 'green-beard effect' whereby genes might make the organism (not necessarily a man) carrying them recognisable to other organisms carrying that gene so that all the organisms carrying the 'green beard' gene would be altruistic towards each other but not to non-green-bearded organisms.
It's not the usual easy read. As the author points out, 'this book ... assumes that the reader has professional knowledge of evolutionary biology and its technical terms'. However, it's well worth the effort of struggling with it if you're interested in evolution and Richard Dawkins ideas about how it all works. If you've read "The Selfish Gene" and found it riveting, you'll probably enjoy this too.