This post is a continuation from The Creation of the World
Unlike physics and astronomy, in which unbiased observation directly contradicted religious teachings, for a long time progress in biology did not challenge old wisdom. Throughout the 16th and 17th centuries the work of biologist was limited to the classification of all known plants and animals into taxonomic groups. While their highlighted the commonalities living organisms shared, the belief that all living organisms had been created in their current form was so well rooted that no serious alternative had been proposed before 1859. This was the year that Charles Darwin shocked his contemporaries by implying that humans and animals shared a common ancestor.
In 1831, Charles Darwin (1809–1882) joined as a naturalist the survey ship HMS Beagle for an expedition around the world. When he returned home in 1836 with over 2000 pages of notes and thousands of skins, bones and fossils, his work had just begun. It took over 20 years before he finally formalized his findings and observations into a consistent theory which he published in his book On the Origin of Species by Means of Natural Selection.
Natural selection theory suggests that adaptation to the environment through the survival of the fittest is the main (though not the only) mechanism of evolution. Random variations continuously occur in species, which are constantly under struggle for resources. When “the surviving one of ten thousand trials” gives an organism an advantage in its environment, it would pass on this favorable change to its offspring. Accumulation of such variations within a population – particularly when major environmental changes occur, and fast adaptation to the new environment is required – could eventually lead to the creation of new species.
It took Darwin many years and many attempts to find a theory that could answer the many questions that perplexed him during his voyage. His theory could explain why fossils of extinct animals carried a close resemblance to existing species. It clarified why each of the Galapagos Islands had its different but very similar species of animals. It also accounted for the existence of creatures that, in Darwin’s view, could never be designed by a benign entity, like the parasitic wasp, which – to Darwin's horror and disgust – stored caterpillars to be eaten alive by its grubs.
Modern evolution theory has evolved considerably since Darwin’s days. However, regardless of the major changes the theory has undergone, the new body of evidence, accumulated from otherwise unrelated fields of science, only strengthen its plausibility. While unlocking the secrets of DNA revealed the engine behind the random variations, microbiology gave empirical evidence that not only do such variations occur regularly, but that they directly impact on human lives, as they are both the cause of new diseases (e.g. aids, bird-flu) and the means for their cure.
Further evidence has been derived by paleontologists and evolutionary molecular biologists, who have been able to fill many of the gaps in the history of species. Evolutionary molecular biology provides the tools to measure the amount of DNA change that differentiates one species from another. This has led to the surprise discovery that the difference in the DNA sequence between human and chimpanzee is no bigger than 2%. Humans were no longer the crown of the creation, but the result of random changes that happened to make them better adapted for survival – Aristotle’s scale of value had lost its meaning.
It is not surprising that evolution theory had evoked such passionate antagonism. This time it was not the Church that rose against it, but the public. Its radical implications were far wider than the populist “we are not monkeys” emotional response that led crowds to the streets. Evolution theory eliminated the need for a designer or a creator, and it undermined what was probably the oldest and most frequently used proof for the existence of God, as first expressed by the ancient Roman Marcus Tullius Cicero (106– 43BC):
When you see a sundial or a water-clock, you see that it tells the time by design and not by chance. How then can you imagine that the universe as a whole is devoid of purpose and intelligence, when it embraces everything, including these artifacts themselves and their artificers?
Those who object to the evolution theory can be broadly classified into two camps: creationists, and the advocates of intelligent design, also known as design theorists. Creationists believe that the literal biblical narration provides a factual account of events, and reject any kind of evolutionary process. Intelligent design, on the other hand, accepts that organisms could evolve from other organisms, but rejects the randomness of the process and suggest that it was preordained and following a blueprint. To use an analogy, when dominoes fall, although each piece falls because it is pushed by its predecessor, the pattern of the fall is predefined by the original setting of the dominoes.
Intelligent design theorists claim that without such a blueprint, biological organs and systems that display irreducible complexity could not have evolved. That is, no random process could account for the development of an organ, like the eye, which is composed of several interacting parts, all required for its functioning. As the evolution anything but the complete, operating organ could not be of any use, it would not have survived the process of natural selection.