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Darwin

Darwin formulated his theory of evolution as early as 1839 when he was 30 years old, but he was so concerned about the hostility his theory might provoke, that he waited twenty years before publishing it. Even then he was forced to do so by his younger friend, Alfred Wallace who had arrived at the same conclusions but wanted to publish immediately in a paper entitled 'On the Tendency of Varieties to Depart Indefinitely from the Original Type'. The outcome was a joint presentation to the Linnaean Society in July 1858 and Darwin hurriedly published his 'The Origin of Species' the following year.

Both Wallace and Darwin had been inspired by reading 'An Essay on the Principle of Population' by Robert Malthus. In his essay, Malthus argued that human population increased faster than the production of food and this would lead eventually to famine or even indirectly to war.

In 1776, Adam Smith, a Scottish professor of logic and philosophy, published a book called 'The Wealth of Nations' in which he proposed that it was in the public's interest to give employers unlimited freedom. Competition would result in the elimination of impoverishing inefficiency by ensuring that only the fittest entrepreneurs survived. It is likely that Darwin's reading of Adam Smith led to his first ideas on 'Natural Selection'.

For many educated people, the Bible no longer gave an adequate scientific explanation for the appearance of life on earth and the 'The Origin of Species' provided just such a scientific explanation. For some, it also conveniently replaced an 'old fashioned religion' with a modern philosophy and it is this that probably accounts for the phenomenal success of Darwin's book.

Darwin's Theory proposes that every living creature has a mother with a continuous ancestral maternal line going back thousands of millions of years and that the mechanism of evolution are small changes selected by Nature for suvival. Since this cannot be proved by scientific deduction, his theory has to rely entirely on fossil evidence. At the time, several eminent geologists such as Adam Sedgewick and Richard Owen pointed out the abrupt rather than the gradual appearance of many distinct forms. A boost for Darwin's theory, was the discovery in 1861 of Archaeopteryx, a fully fledged bird with some reptilian features such as teeth - an obvious candidate for an intermediate fossil.

In 1876 Thomas Huxley, a distinguished British biologist and a close friend of Charles Darwin, was introduced to U.S. paleontologist O.C. Marsh and his large collection of horse fossils. While horses went extinct in North America some 10,000 years ago, horses originated there before dispersing around the globe. With Huxley's publicity, Marsh's collection soon came to be seen as a classic example of how an animal's evolution could be traced back through a single line. This sequence, from the earliest forest dwellers to modern-day savanna zebras, has since been reproduced in countless textbooks and natural history museum exhibits.

Horse evolution was never as straightforward as Marsh's smooth fossil sequence suggested and its ancestral tree sprouted numerous branches, many of which led to species that no longer exist. The simple 'ladder' has now had to be replaced with bushy diagrams such as that shown above.

Darwin's Theory is of immense importance since it has taken us away from an 'interventionist' theory of life to a natural one and it is now upheld by the majority of scientists. The problem with the theory is that it is only partially true - natural selection clearly does cause gradual changes that ensure the survival of a species. It can even, as Ernst Mayr has pointed out, create new species if a group becomes completely isolated from its origins. But this ability to change is built into life itself. Today we know far more than Darwin about the complexities of genetics and we now know that it is this 'built-in' variability that Darwin and Wallace observed. Even if gradual changes could create new species, they are unable to explain how complex life, with its kingdoms, phyla, classes and orders, originated in the first place - before this built-in variability existed. It is also far from proven that small adaptations can, of themselves, create say the eye of an eagle or the ear of a shark. It is therefore quite reasonable to suppose that there is, as yet, some unknown mechanism involved.

To believe that there may be some unknown factor involved in the creation of the living world does not mean going back to a 'God of the Gaps', but it does mean scientists facing up to the truth rather than cling to an outdated paradigm as did the Catholic Church with Galileo's discoveries, four hundred years ago.

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