Charles Darwin (Fig. 1) developed the first naturalistic mechanism for evolution, that of natural selection, thus explaining the diversification of life through a lengthy process of change by adaptation. He was born in Shrewsbury, England, the fifth of six children of Robert and Susannah Darwin (née Wedgwood), and the grandson of Erasmus Darwin, and of Josiah Wedgwood.
After finishing school, Darwin studied medicine in Edinburgh in 1825. His dislike for dissection and the brutality of surgery at the time led him to leave the medical school in 1827. Whilst there, however, he was influenced by the Lamarckian Robert Edmund Grant.
His father, concerned by his son's apparent academic failure, and fearing that he would become a "ne'er do well", enrolled him at Cambridge to read Theology, with the hopes of Charles eventually becoming a parson. While at Cambridge, he came under the intellectual influence of scientific minds cuch as William Whewell andJohn Stevens Henslow who, (combined with his interest in collecting beetles, which was encouraged by his cousin, William Darwin Fox), resulted in him pursuing natural history.
Darwin planned to visit Madeira with some class-mates upon graduation in 1831. These plans, however, fell through and after Darwin finished his studies, Henslow recommended him for the position of gentleman's companion to Robert Fitzroy, the captain of HMS Beagle, which was departing on a five-year expedition to chart the coastline of South America.
Prior to departure, Darwin spent a few weeks with the geologist Adam Sedgwick mapping strata in Wales. It must be noted that (aside from a few lectures that he endured in Edinburgh) this was Darwin's sole exposure to formal geological study.
Darwin's work during the expedition allowed him to study both the geological properties of continents and isles and a multitude of living organisms and fossils. During his voyage, he visited the Cape Verde Archipelago, the Falkland Islands, the South American coast, the Galapagos Islands and Australia, collecting considerable quantities of specimens.
After returning from the voyage in 1836, Darwin analyzed the specimens he collected, and noticed similarities between fossils and living species within the same geographic area. In particular, he noticed that every island had its own kind of tortoises and birds that were all slightly different in appearance, favored food etc., but otherwise quite similar. This observation was especially apparent among the specimens collected on the Galapagos Islands. He developed the theory that, for example, all the different turtles had originated from a single turtle species, and had adopted to life on the different islands in different ways.
Based on these thoughts, he formulated his thoughts about the changes and developments of species in his Notebook on the Transmutation of Species, which was in accordance with Lyell's Principles of Geology and Robert Malthus' Essay on the Principle of Population, which stated that the size of a population is limited by the food resources available. (This needs to be seriously revised, as it does not adequately represent the maturation of Darwin's thoughts. John Lynch Agreed. sjc).
In 1842, Darwin formulated a short "Pencil Sketch" of his theory and by 1844 had written a 240 page "Essay" which provides an expanded version of his early ideas on natural selection. Between 1844 and 1858, when he would prevent his theory to the Linnean Society of London, Darwin would modify his theory in a number of ways.
Darwin married his cousin Emma Wedgwood in 1839. After living for a number of years in London, the couple eventually moved to Downe House, in Downe, Kent. Darwin and his wife had ten children, three of whom died early. Between 1839 and 1843, Darwin's Zoology of the Voyage of H.M.S. Beagle was published in five volumes. (Need more on publications)
On July 1, 1858, Darwin's paper about The Origin of Species by Means of Natural Selection was read to the Linnean Society in London, on the same day as a paper from Alfred Russel Wallace, who had developed a similar theory independently. (Expand)
Darwin's book On the Origin of Species by Means of Natural Selection was published one year later, and was of sufficient interest to have the publisher's stocks completely sold to bookstores on the first day. In his later books The Variation of Animals and Plants Under Domestication (1868), The Descent of Man, and Selection in Relation to Sex (1871) and The Expression of Emotions in Animals and Man (1872), Darwin expanded on many topics introduced in Origin of Species.
In spite of some criticism, the value of Darwin's work was appreciated throughout the scienctific community. He became a member of the Royal Society of London in 1839 and of the French Academy of Science (l'Académie des Sciences) in 1878. Darwin died in Downe, Kent, England, on April 19, 1882 and was buried in Westminster Abbey.
Darwin was given particular recognition in 2000 when his image appeared on the Bank of England ten pound note, replacing Charles Dickens. Reportedly his impressive and supposedly hard to forge beard was a contributing factor in this choice.
Before the nineteenth century, the accepted theory for the extinction of species was called Catastrophism, which stated that species went extinct due to catastrophes that were often followed by the formation of new species ex nihilo (out of nothing). The extinct species can then be found as fossils. The new species were considered unchangeable. This theory was in accordance with the story of the Flood in the Bible. In the early nineteenth century, several new theories started to compete with Catastrophism. One of the most important ones was developed by Jean-Baptiste Lamarck (1744-1829). He observed that every new generation inherits the traits of its ancestors. He suggested that traits or organs become enhanced with repeated use and weakened or removed by disuse in each individual, who will pass these improvements or losses directly to their offspring. In 1830, the British geologist Sir Charles Lyell disproved the Catastrophism Theory, but held on to the theory of species staying unchanged during time. Lyell founded uniformitarianism, a theory stating that the surface of earth changed slowly through eons by constant forces.
The Structure of Darwin's Theory
Darwin's theory of evolution states that all individuals of a population are different from each other. Some of them are adapted better for their actual environment than the others and have therefore better chances to survive and procreate. That way, their genetic properties are given to the following generations, becoming dominant among the population throughout time (Fig. 2). This gradual and continuous process results in the evolution of species. The four key points of his theory were :
- Evolution does occur
- Evolutionary change is usually gradual, requiring thousands to millions of years
- The primary mechanism for evolution is natural selection
- All species alive today originated from a single life form through a branching process called specialization
Figure 2 : Schematic drawing of the evolution process.
(1) Natural selection. (2) Reproduction. (3) Mutation.
The Response to Darwin's Theory
After the publication of Darwin's book, evolution as the means of natural selection was widely discussed (Fig. 3), particularly by the religious and the scientific communities. Though Darwin was supported by some scientists (e.g., T.H. Huxley), others hesitated to accept the theory due to the unexplained ability of individuals to pass their special abilities to their offspring. The last point remained a mystery until the existence of genes was discovered. In 1874, the theologian Charles Hodge accused Darwin of denying the existence of God by defining humans to be a result of a natural process rather than a creation designed by God. Even today, many Christian and other religious fundamentalists continue to fight the Darwinian theory of evolution. Darwin's theory is now backed up by the comparison of DNA from different organisms which shows the closeness of their relationship.
Contrary to popular opinion, Darwin did not "discover" evolution as it was accepted by many since the beginning of the 1800's. Instead, he provided the first really coherent theory of how evolution occurs (via the mechanism of natural selection). Other important aspects of Darwin's overall theory were: common descent, sexual selection, gradualism, and pangenesis. It is important to remember that Darwin's version of natural selection was different from that presented by Wallace in that he held that natural selection was continuously operating, whereas Wallace argued that selection only occurred when the environment changed.
Figure 3 : Caricature of Darwin as an ape in the Hornet magazine. (Image in the PD)
Ospovat, Dov ....
Desmond, Adrian & James Moore, Darwin
- 'Expression of Emotions in Man and Animals' http://paradigm.soci.brocku.ca/~lward/Darwin/darwin00.html
- 'Life and Letters of Charles Darwin' http://digital.library.upenn.edu/webbin/gutbook/lookup?num=2010
- 'Descent of Man' http://www.infidels.org/library/historical/charles_darwin/descent_of_man/
- 'Formation of vegetable Mould Through the Action of Worms' http://digital.library.upenn.edu/webbin/gutbook/lookup?num=2355
- 'Geological Observations of South America' http://digital.library.upenn.edu/webbin/gutbook/lookup?num=3620
- 'Geological Observations of Volcanic Islands' http://digital.library.upenn.edu/webbin/gutbook/lookup?num=3054
- 'Movement and Habits of Climbing Plants' http://digital.library.upenn.edu/webbin/gutbook/lookup?num=2485
- 'Structure and Distribution of Coral Reefs' http://digital.library.upenn.edu/webbin/gutbook/lookup?num=2690
- 'Variation of Plants and Animals Under Domestication' http://www.esp.org/books/darwin/variation/facsimile/title3.html
- 'Voyage of the Beagle' http://www.infidels.org/library/historical/charles_darwin/voyage_of_beagle/
- 'Autobiography of Charles Darwin' http://digital.library.upenn.edu/webbin/gutbook/lookup?num=2010