Posted: Fri, February 03, 2017 | By: Humanism
By SNS On · in General, Member Articles Add Comment
On 12 February Humanists and many others celebrate Darwin Day. We do this to recognise the life work of Charles Darwin, which is characterized by
- intellectual rigour,
- perpetual curiosity and
- a hunger for truth. The simple version of ‘the Darwin story’ tells of him doing a 5-year voyage around the world, observing and collecting specimens. He then marries, settles down to mull over his collection and to write numerous papers and books including The Origin of Species. In this world-famous book he gives a detailed case for life having evolved by natural selection.
The fuller version tells that Darwin ‘stood on the shoulders of others’, i.e. he relied on the contributions of many others such as animal breeders, naturalists, scientists and philosophers, when setting out the arguments for natural selection. Knowing the fuller version doesn’t lessen Darwin’s world-changing contribution, it just tells a truer story.
Charles Darwin’s life – in brief
Darwin was born 12 February 1809 into a middle-class English family. From boyhood he had a keen interest in nature. This grew into a serious pastime, when he began spending time with naturalists, like John Henslow, Professor of Botany at Cambridge University. It was Henslow who enabled Darwin to take the position of naturalist and gentleman companion to Captain James FitzRoy on the research ship HMS Beagle.
During the five-year-long voyage around the world (1831–36) Darwin collected a vast number of specimens and made detailed observations of the natural world. On his return to England he used this material as the basis for further experimental work. This resulted in Darwin writing four major books and numerous papers and monographs.
He was fortunate to have an independent income, further augmented by marrying his well-off cousin Emma Wedgwood in 1839. The couple settled in Downe, Kent, and had 10 children, seven of whom survived to adulthood.
Darwin lived during a time of great change through political, economic and religious forces, along with advances in science. For example, it was evident to scientists that the universe was vastly bigger than previously supposed. And railway cuttings and canal excavations were revealing multiply layered sedimentary rocks, many embedded with strange fossils. This indicated the Earth was much older than previously claimed and subject to change. This led many to suppose that it was also likely for plants and animals species to change.
Yet up until the mid-1800s it was believed that all species were fixed in the form in which they first appeared. This idea, known as the fixity of species, matched both everyday experience and the religious idea of God creating all species at the same time.
However, lurking as an under-current to this accepted view was the idea that life had evolved from simple to more complex forms, i.e. life forms were changeable. First suggested by the early Greeks, it was an idea that was gathering more adherents, including Darwin’s grandfather Erasmus. Despite the apparent logic of life forms changing, no one had proposed a plausible mechanism for how this might occur.
However, naturalists did have some observations that made them wonder just how fixed species really were. One was the well-known fact that while individuals usually bred with members of their own species, sometimes related species interbred with varying degrees of success, e.g. horses and donkeys. Such examples of cross-breeding showed that the boundary between species was not clear-cut.
Another set of observations was provided by fossil remains. These revealed the existence in the past of beings similar to living types as well as specimens that had no living representatives.
While we usually think of Charles Darwin as the person who came up with the idea of natural selection, he wasn’t the first to publish. That honour goes to another naturalist, Alfred Wallace, who wrote a paper about the transmutation of species in 1855. Although that paper was not well received, Wallace persisted with his ideas and wrote another paper in 1858, again outlining the process of natural selection. At the time he was collecting specimens in the Moluccas, so he sent his paper directly to Darwin.
Being naturalists who had travelled widely and mulled over the variation and distribution of species, and read the relevant earlier work by other scientists, both Wallace and Darwin independently came to the following interpretation of how species could change.
This process of differential survival and reproduction is called natural selection. It enables each species to change or evolve over time, thereby refitting themselves to altered environments.
- Individuals in a species vary.
- More offspring are produced than can survive.
- Those that survive have advantageous features, i.e. some are better adapted to the environment.
- If the environment changes, different but better-adapted individuals survive.
Darwin, who had been systematically working on the idea of natural selection, was yet to publish. When he read Wallace’s latest paper he was devastated. In science parlance he appeared to have been ‘pipped at the post’, for failing to publish first.
But Darwin’s scientific confidants Dr Joseph Hooker (Royal Botanic Gardens, Kew) and Sir Charles Lyell (Professor of Geology at King’s College London), who knew he had also been working on the same idea, organised for papers by both Wallace and Darwin to be jointly presented at a meeting of the Linnaean Society in London, 1 July 1858. Thus both can be credited with outlining natural selection.
Darwin then spent the next year revising and finalising a lengthy book he had long been working on. It was published on 24 November 1859 as On the Origin of Species by Means of Natural Selection. Later known by a shorter title, The Origin of Species, Darwin repeatedly revised his magnum opus, with each new edition, until his death in 1882.
Ultimately it was not the 1858 papers, but Darwin’s book that convinced other scientists and much of the wider public, that natural selection could explain how species change and life evolves over time. Hence the reason we celebrate Darwin Day.