On the Natural Selection of Charles Darwin
A Review of The Origin of Species
Around the middle of the nineteenth century, an Augustinian friar, physicist and mathematician called Gregor Mendel experimented with pea plants and, without realising it, founded a whole new field of scientific endeavour. Mendel’s valuable contribution to science became known and recognised only after his death in 1884. If Charles Darwin knew of his work at all, and it has been argued that he did, he clearly did not recognise its significance. Had he done so, it seems possible that the progress of evolutionary theory, and of heredity, might have taken quite a different course. Now that our understanding of the evolutionary process has been illuminated by the study of genetics, many of the ideas expressed by Darwin seem quaint to say the least. Some of his conclusions – though, to be fair, he often admits he doesn’t know the answers – are just wrong. Be that as it may, we can surely share his awe that “from so simple a beginning endless forms most beautiful and most wonderful … are being evolved.”
Darwin’s groundbreaking work, On the Origin of Species by means of Natural Selection etc etc, first published in 1859, received a mixed reception from its readers, perhaps more because of what many thought it implied, rather than because of what it actually said. That is, the logical extension of the theory of natural selection was that homo sapiens too had evolved from the animals, a concept that was in violent opposition to the teachings of the Christian Church. Even today, Darwinian ideas provoke strong emotions on both sides of the science/religion divide, and it is near impossible to review The Origin of Species without sparking anew the controversy surrounding this seminal work. Darwin realised his arguments would stir deeply entrenched beliefs, but he saw “no good reason why [his views] should shock the religious feelings of anyone.” It is a sentiment I share and feel obliged to express.
The truth is that homo sapiens has been aware of evolution by adaptation and selection for many centuries. The great Persian polymath Nasr ad-Din Tusi wrote in the thirteenth century that “organisms that can gain the new features faster are more variable. As a result they gain advantages over other creatures.“ Humanity has promoted and encouraged selection, not always in the best interests of the species (neither ours nor those with which we have experimented). And it is with this fact that Darwin begins his great work, supplying much embryonic support for his theory from the practices of selective breeders of dogs, pigeons and other organisms. In the second chapter, he turns to the consideration of the same process in nature, positing that what man can do nature can surely do better. However, the burning question remains: how do varieties become incipient species, incipient species transform into species, and species into genera? The answer is that it’s a matter of definition, as the author is fond of pointing out.
The theory of natural selection, which Darwin outlines in the third and fourth chapters, is simple and maybe, to our 21st century minds, obvious. All living organisms struggle with nature; they compete for limited resources. There are predators and there are prey; some creatures are both. And it is only by adapting and changing, by acquiring characteristics that enable them to prosper, that some living beings survive to reproduce while others do not.
Darwin’s scientific opponents focussed on three apparent problems with the theory: the absence of intermediate forms, the sterility of hybrids and the weak support from the fossil record. Some others argued that the apparent ‘wonders’ of, for example, the human eye, or the fully developed instincts in the ant and the bee could not be explained by the evolutionary process. Darwin himself was only too aware of the criticism and in the middle chapters of his book he endeavours to answer it. By clever reasoning, and example from his own experimentation and that of other naturalists, he demonstrates that his theory does not break down because of these difficulties. The chapter on instinct shows Darwin at his best as an experimental observer of nature. The sections on slave ants and hive-making are among the most intersting passages in the whole book.
There follow chapters on the migration of species throughout the world with descriptions of both differences and similarities between related organisms. Darwin discusses in detail how the glacial period, the ice ages and the probable changes in the shape of land masses have contributed to the distribution of forms we see today. Finally, he discusses embryology and focusses on the striking similarities between the foetal stages of different species and genera, offering these facts as support for his theory.
“The laws governing inheritance are for the most part unknown.”
The Origin of Species is not a book of popular science, rather it is an academic dissertation by one naturalist addressed to others of his profession. Thus it is, in places, difficult for the non-naturalist to follow. Sometimes, Darwin seems to be arguing in circles. On the basis of Origin alone he does not quite make his case. By his own admission, he did not understand the precise mechanism of natural selection, nor did even he appreciate the many aeons of geological time available for evolutionary adaptation. Mid 19th century science grossly underestimated the age of the Earth and to that extent Darwin was very much a man of his time. These are the real weaknesses in his presentation. Yet, in a sense, they are strengths too. Darwin arrived at his theory of natural selection despite these disadvantages. Armed with an additional century-and-a-half of scientific knowledge and discovery, we know today that most of his conclusions were valid and his leap of faith entirely justified. We can read The Origin of Species and marvel that its author got so much of it right.