Darwin’s theory of evolution: Survival of nature’s fit!

Abstract

Even after 200 years after his birth, Charles Robert Darwin and his work are still central to any discussion on evolution. What is the relevance of evolution as Darwin perceived it? What were the pre-Darwinian, Darwinian and post-Darwinian pictures? Among the ancient pre-Darwinian theories Aristotle’s ‘Scala Naturale’ and the ‘Special Creation’ theory are perhaps the most important, whereas Lamark’s theory of ‘Evolution’ and Lyell’s theory of ‘Uniformitarianism’ are perhaps the most important modern ones, before Darwin’s work. His voyage of circumnavigation on the Beagle lead to pertinent observations: the similarities of structures between fossils and living forms in the same area; the presence of related but different species in adjacent areas of the same continent; the resemblance of species on isolated islands to those of the nearest continent and differences between species on closely adjacent islands of the Galapagos Archipelago in relation to their modes of life and feeding; natural selection and survival of the fittest. The conclusions arising out of these and other observations were published as “The Origin of Species by means of natural selection or the preservation of Favored Races in the Struggle for Life”. But Darwin’s theory could not explain how the variations favored by natural selection initially arose or were inherited; the lack of intermediate forms and the long time frame needed for the changes to occur were two further objections to it. However, in the post-Darwinian era beginning with the rediscovery of Mendelism to modern day molecular biology, and the inputs from radioactive dating, these and other queries have not only been answered but they also strongly vindicate Darwin’s theory that has indeed stood the test of time and has emerged as the most convincing and fittest of all!

Man has always wondered where he came from, wondered what his origins were and wondered spellbound at the wonderful variety of life around him! Was he a demigod, a spectator or participant in the natural scheme of things? May be on a star studded night, when man looked up at the sky and wondered, he became mankind. It is probably this single quality of wonder, more than anything else that made Charles Darwin synonymous with evolution in particular and biology in general. Even two hundred years after his birth, Charles Robert Darwin and his work are still central to any discussion on evolution. Darwin was an ‘evolutionary’, with a M.A. degree in theology and with an unquenchable thirst for natural history! Darwin carefully marshaled his facts for more than two decades after his return from the famous Beagle voyage before publishing his magnum opus in 1859. Through this book, he set out to provide evidences that all life is interrelated and life forms are mutable; that they evolve from the simple to complex forms directed by nondeterministic natural selection; and the changes that make the organism suited to its environment and are passed onto the progeny result in descent with modification. The theory made change in organisms an irrevocable part of life. It created a controversy, because to accept this change would be going against certain religious dogma. But change is an inescapable fact of life. Is it therefore true that “nothing in biology makes sense except in the light of evolution”?¹

In the century and half since publication of this book, the rapid advances in Biology have lead to investigating the very molecules that make up life! From the first detailed description of the nucleus in 1830 to the elucidation of the human genome is a mere 170 years! In this quickly progressing scenario, what is the relevance of evolution as Darwin perceived it? What were the pre-Darwinian, Darwinian and post-Darwinian pictures? And, how are they relevant today?