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Book Review: The Greatest Show on Earth: The Evidence for Evolution by Richard Dawkins

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In 2008, a Gallup poll in the US showed that 44% of people believed that God created human beings pretty much in their present form at some time in the last 10,000 years. In the UK, the Ipsos MORI poll of 2006 showed the equivalent figure to be around 22%.

For many people then, the whole idea of evolution is considered as false. Since many of those people who think that way are in positions of power, for example, running educational establishments or political organisations, there is a powerful lobby against evolution.

Scientists though regard evolution as the most successful scientific theory ever, with so much independent evidence, that they cannot understand why it should ever be rejected. So the question is, if the evidence is so clear and obvious, why isn't it accepted?

One answer is that perhaps the evidence is not as clear cut, or as abundant, as scientists claim. Another is that perhaps, the theory of evolution is not well-understood and for that reason, is not accepted. A third possibility is that the evidence itself has rarely been presented in its abundance with an explanation that is convincing. Another possibility is that vested interests have steered potential students away from the evidence.

Richard Dawkins has published a great deal of scientific material on the theory of evolution, most notable in his book The Selfish Gene, which building on Darwin's theory of evolution, explained evolution from the point of view of the gene. His further work explored the implications for evolution of new discoveries in biology, particularly genetics. All of this could well have been over the heads of the general reader.

It was the recognition that the demand for an exposition of the evidence was reasonable, that prompted Dawkings to write The Greatest Show On Earth. Although evolution is demonstrably a fact, many people still do not accept it. Dawkins sets out to present the evidence.

Biologists make a distinction between the fact of evolution, and the theory of evolution, namely natural selection. That evolution is a fact is based on the demonstrable evidence that all living things are related, are cousins, and somewhere along the line, have common ancestors. The theory of evolution is that theory which explains how evolution works, what drives the successive modification of species. Natural selection is a theory that explains the fact of evolution and although some biologists offer modifications to the theory, or even different theories, they are all trying to explain adequately that fact: evolution.

Dawkins shows in careful detail how humans have deliberately modified species throughout history, developing breeds of dogs and cows, and refining plant species to provide abundant crops. In this way Dawkins shows the reader that selection is a powerful mechanism for the modification of species, accentuating particular characteristics. This we are all familiar with.

The mechanism of unnatural selection is a tool humans have used for generations. It works over a period of generations and even in the space of just thirty-five generations, the Russian geneticist Dimitri Belyaev was able to develop a tame affectionate generation of wild foxes, notoriously difficult to handle. The relatively short number of generations is what is interesting here. Unnatural selection, just selective breeding, could accomplish major change in a relatively short time. What then could happen over a very long period of time, perhaps millions of years?

In order to understand the evidence for evolution, we have to understand the timescales and the methods used to study changes over such long periods of time. We need some kind of clock, and there are many to choose from. Dawkins explains in the course of the book, the atomic clocks of radioactive elements, the molecular clocks based on genetics, and dendrochronology, the measurement of tree rings. With our clocks at the ready, we can start to measure changes on different timescales and start to piece together the changes which took common ancestors to their differentiated descendants.

It is a common misunderstanding about evolution that humans are descended from chimpanzees. The truth is that humans and chimpanzees have a common ancestor, which was neither human nor chimp. The intermediates linking humans back to this common form are abundant, and there is overwhelming evidence both from fossil remains and genetics to convince even the most ardent critic.

Such misunderstandings produce demands from creationists for evidence of hybrid species such as crocoducks, a doggypotamus, or a kangaroach. Dawkins explains patiently why such a question is nonsensical. No modern species is directly descended from any other modern species. They have common ancestors.

Dawkins explains how geographical distribution is explained by the idea of population islands which are prevented from mixing their genes with their neighbours. It could be a mountain range, or a sea which provides the barrier. These barriers do not appear overnight, by in geological time, in hundreds of thousands, or millions of years, creating a genetically isolated population whose future evolutionary path will be distinct. That is why we end up with lemurs in Madagascar and nowhere else, why Australia had only marsupial mammals (and bats who could fly there). The fact of continental drift explained the biological variation between countries. The evidence leaves no doubt that this is the case.

Having demonstrated the fact of evolution, Dawkins takes the second half of the book to bring us up to date with modern developments. He shows how using genetic techniques, it is possible to construct in great detail, the tree of life, tracing back very many species to their ancestors, showing how species and families are related. He looks at the evidence from skeletons showing how tiny advantageous mutations resulted in better adaptation and an increased survival rate of the species.

In the last chapter, Dawkins gets a little more philosphical and looks at the issue of pain and suffering in nature. It has long been a problem for religious people to explain how a benevolent god can permit suffering on an absolutely massive scale in nature. Why for example, has a gazelle not developed a last minute anaesthetic to save it pain when it is finally caught by a lion? Such needless suffering demands an explanation.

The explanation is in terms of the economy of natural selection. Developing new functionality costs resources because it is diverting energy needed in development away from something that is already there. So unless the new feature, a very small change, increases the likelihood of survival, it won't be inherited through the genes. That's exactly the case of the anaesthetic for the gazelle. By the time it might be needed, the gazelle is already condemned. So there's no evolutionary advantage.

This utter insensitivity of evolution is shocking to some, and it conflicts with how we'd like nature to be. But the evidence itself shows that evolution is blind. It doesn't aim towards higher development, it doesn't lead to man as the highest form. Its motor is survival.

And that brings out another remarkable feature of this book, that of the notion of design. Just one example will suffice to show that idea of an intelligent designer does not fit well with even the mammalian body let alone all the other forms of life.

In mammals there is a nerve called the recurrent laryngeal nerve which comes from the brain to feed the larynx. Unfortunately, it goes down into the chest, loops around a branch of the aorta, and then comes back up, a detour of around six inches. Clearly a design fault — any designer would cut out the loop, save tissue and increase efficiency. In adult giraffes, that design fault costs them a detour of 15 feet.

Natural selection can easily explain these curious facts through an understanding of embryology, and this is one of the most fascinating parts of the books, vividly bringing home how we are related to other forms of life on earth.

The book is beautifully written, teeming with information and explanation, and presents the overwhelming evidence for the fact of evolution. It would be strange indeed if, given the opportunity to see this evidence, so many people would remain unconvinced.

It remains to be seen whether schoolchildren and students will be permitted open access to this resource in their classrooms, or whether, as has happened in so many places, religious opposition will restrict their opportunity to learn about the greatest show on earth.

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About Bob Lloyd

  • http://corp-minamiji.typepad.com Christy Corp-Minamiji

    Nice review. Particularly liked the bit about the philosophical aspect.