Charles Darwin is perhaps the world's best known scientist. Every schoolboy knows him as the originator of the theory of evolution. But today, the idea that various species evolved out of natural selection ' that is, out of mutual competition and adaptation to the environment ' looks obvious. Why did it need to be propagated'
As soon as the first human ' or dinosaur as the case may be ' learnt to think, he ran into certain elementary questions. Where was I before I was born' Where did my father go when he ceased to breathe' The questions in themselves imply the existence of other worlds which we can know nothing about. Many models of such worlds can be imagined. None of them is testable, and all of them are speculative. Elaborate stories can be told, retold and passed on to posterity.
The story in the tribe in which Darwin was born was that there was one God, and that he constructed the world in six days and rested on the seventh. The world included all living beings. Thus from the day the world was finished some 6000 years ago, every species from jellyfish to ant-eater had existed unmodified. The Bible begins with this story, and its repudiation entailed the dismantling of an element of the Christian faith ' the creationist element. Darwin propagated what was then considered blasphemy.
But he was no Galileo. He was the son of a doctor who sent him to Christ's College, Cambridge, in the hope that he would become a clergyman or classicist. Charles showed aptitude for neither. But he used to go for walks in the countryside with J.S. Henslow, the Professor of Botany. When the Admiralty decided to send a ship to survey the southern hemisphere, Henslow recommended Charles, who was taken on it as naturalist. HMS Beagle, a ten-gun brig, left Davenport on December 27, 1831, after being beaten back twice by unfavourable winds. It sailed to Cape Verde Islands, and then down the east coast of South America. Then it sailed across the Magellan Strait and up the coast of Chile and Peru, and stopped in the Galapagos. Then it sailed across the Pacific to New Zealand and Australia, and on to Mauritius. In Port Louis, he saw his first Indians. 'Convicts from India are banished here for life; at present there are about 800, and they are employed in various public works. Before seeing these people, I had no idea that the inhabitants of India were such noble-looking figures. Their skin is extremely dark, and many of the older men had large mustaches and beards of a snow-white colour; this, together with the fire of their expression, gave them quite an imposing aspect. The greater number had been banished for murder and the worst crimes; others for causes which can scarcely be considered as moral faults, such as for not obeying, from superstitious motives, the English laws. These men are generally quiet and well-conducted; from their outward conduct, their cleanliness, and faithful observance of their strange religious rites, it was impossible to look at them with the same eyes as on our wretched convicts in New South Wales.' Then the Beagle rounded the Cape of Good Hope, and finally reached Falmouth on October 2, 1836. That is how he encountered animals and birds of South America and Australasia.
So he started thinking about the variety of living beings and how it came about. He planned a detailed treatise, and would have spent a lifetime writing it. But in 1858 ' 22 years after the Beagle returned ' Alfred Wallace, a self-made naturalist, sent Darwin a paper which applied Malthus's idea of survival of the fittest to all life and thus anticipated the theory of natural selection. In a quandary, Darwin consulted Charles Lyell (Professor of geology in King's College, London) and Joseph Hooker (leading naturalist of the mid-nineteenth century). They placed Wallace's paper before the Linnaean Society, together with scattered writings of Darwin that established his priority. After that, Darwin was compelled to put down his ideas on paper. The Origin of Species was first published in 1858. Although close to 200,000 words, it was supposed to be a summary of his views; he never managed to write the extended version.
Although the book is an attack on received theory, Darwin does not criticize any of its proponents by name; instead, he draws support from as many of his predecessors as possible. Instead of claiming priority or novelty for his own views, he makes it out as if wiser men had thought them first. Darwin takes one contrary argument after another, and sets out to controvert it as gently as possible. He marshalls masses of evidence, but concedes its weaknesses.
Thus, creationists used to cite the sterility of cross-breeds, such as mules, as evidence that God had a monopoly of creation of species. Darwin says that sterility resulted when crossing disturbed reproductive systems, and was by no means universal; in many cases of controlled cross-breeding, fertility actually increased.
If all species evolved by gradual modification in response to the environment, the world should display all the minor intermediate variations. For instance, the world's cattle should not be divided into a few breeds, but must include minute variations. The reason they do not, according to Darwin, lies in competition. Successful varieties multiply faster; their competition leads less successful variations to become extinct. Thus natural selection leads to a small number of numerous varieties.
If intermediate varieties died out, they should be found amongst fossils, the entire range, extinct and surviving, should have been preserved in rocks. But actually, fossils belong to a much smaller number of strongly varying species than do live animals. This, according to Darwin, is because geological evidence is extremely incomplete. Fossils are found in sedimentary rocks. In other words, animals were fossilized when land was sinking, and skeletons were submerged in water and buried in sand. Except in periods and regions where this happened, the record of skeletons would be wiped out. So the wide differences amongst fossilized species only reflect the rarity of fossilization.
Many animals, birds and plants are found on islands and in areas between which there is no land connection; that could be evidence that God had created them separately in situ. Darwin rejects the idea that the common species must have been separated when continents drifted apart and islands were created. Birds, according to him, fly enormous distances. Animals and insects are often carried long distances on driftwood. But most of the separation of common species must have occurred when the last ice age ended and ice bridges across seas melted. He shows that species, such as bats, which can fly long distances, are more widely diffused across the world than those that cannot; and that the further away an island is from the nearest continent, the fewer varieties it has.
Despite his detailed argument and conciliatory approach, Darwin's theory won ground only slowly; there are Americans even now who believe that God created all beings at the same time. The Origin of Species is still worth reading for its courtly language, and as an exercise in persuasion.