During the 17th and 18th century classification of the natural world led to the observation that species of plants and animals are found as variations on common themes. It is this observation that impressed many naturalists and in the 19th century led Charles Darwin to seek an explanation.
A general belief in direct creation by God prevailed in Christian Europe at this time. But by the 19th century, naturalists generally believed in the continuous special creation of each species of plant and animal, while varieties belonging to species were believed to be produced by secondary causes. The secondary causes included the artificial breeding of animals and cultivation of plants by Man to produce a great diversity of varieties. It was known that extinctions had occurred in past geological eras and that ancient forms of life found as fossils are no longer found living today. It was thought by many that God replenished the Earth with the creation of new species after extinctions had occurred; there was a general belief in Progressive Creationism.
Over the course of the famous five year voyage around the world as naturalist on board HMS Beagle between 1831 and 1836, Charles Darwin became convinced that species are not fixed. Many years later, after much work on barnacles, beetles, orchids and all manner of other natural things including a hobby in pigeon fancying, Darwin wrote On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life published in 1859.
In The Origin of Species Darwin argued against the doctrine of the creation of each separate species. Belief in the design of each species of plant and animal by God was known as the fixity, immutability or permanence of species.
There had already been some attempts at an evolutionary understanding of the world, the most famous of which was proposed by the French naturalist Chevalier de Lamarck in Zoological Philosophy (1809). Lamarck’s evolutionary ideas were quickly rejected, although the term ‘biology’, which he coined, became widely used. Darwin’s own grandfather, Erasmus Darwin (1731-1802) also held evolutionary views. Erasmus Darwin was a free thinker and political radical, who founded a philosophical society in Derby. He had an unusual talent for writing scientific treatises in rhyming verse. Erasmus Darwin wrote Zoonomia or the Laws of Organic Life in 1794-1796 in which he expressed the notion that species modify themselves by adapting to their environment with purpose residing in the desires of the animal itself. Lamarckism was similar to this view.
Vestiges of the Natural History of Creation (1844) published anonymously by the Scottish autodidact and publisher Robert Chambers also had some influence at the time. The case for evolution in Vestiges rested upon the observation that fossils found from the most ancient to the most recent geological strata demonstrate a gradual ‘ascent’. It was proposed that new species could arise by sudden mutations in the course of reproduction. These ‘hopeful monsters’ met with much ridicule from other naturalists and professors such as Adam Sedgwick. However, Sedgwick argued against Vestiges on the grounds of theology, rather than science. (The geological collection of Adam Sedgwick is kept at Cambridge University and is open to the public).
Evolution was ‘in the air’, especially among families with progressive ideas such as the Darwins, but Charles Darwin went much further. He hit upon a new idea and followed it up with detailed scientific arguments. Darwin proposed what he described as a principle of evolution and laws of variation in organic beings; he named the principle Natural Selection. Natural Selection, as conceived by Darwin, is a natural process which is not guided towards any defined purpose or preconceived goal. Even so, Darwin believed that the principle would have been set up by God in the beginning with the creation of the first forms of life.
In how Natural Selection stands in relation to the Creator, Charles Darwin suggests that the Creator created the laws of science. Darwin states emphatically in letters such as in a letter written to Asa Gray dated 22nd May 1860, that he never had the intention to write “atheistically” (Francis Darwin 2000, page 249). Darwin writes in this letter, “I am inclined to look at everything as resulting from designed laws, with the details, whether good or bad, left to the working out of what we may call chance.” Further down Darwin concludes, “I can see no reason why a man, or other animal, may not have been aboriginally produced by other laws, and that all these laws may have been expressly designed by an omniscient Creator, who foresaw every future event and consequence.”
Within Darwin’s concept of Natural Selection described in The Origin of Species there are three main strands of evolutionary thought. I will explore the three strands of evolutionary thought under the subtitles Modified traits, Highly perfected organs and Replacement of less-improved forms.