Charles Darwin (1809-1882) was a British naturalist who is famously associated with the term ‘natural selection’ which he believed was the process that caused species to evolve. In this essay I aim to explain Darwin’s theory of evolution through natural selection, contrast it with other similar theories set before it and then an overall conclusion.
Darwin originally studied medicine at Edinburgh University but had an interest in natural history where he was influenced by the work and evolutionary theory of French naturalist Jean-Baptiste Lamarck (1744-1829). In 1831 Darwin joined a five year exploration ship, The Beagle, where he read the ‘Principles of Geology’ (1830), the works of geologist Charles Lyell (1797-1875). Lyell comments on the change in rock sediments and suggests that fossils found in rocks may be proof that animals lived thousands, if not millions of year previously. This influenced the ideas of Darwin greatly.
During the explorations of The Beagle, Darwin discovered several different types of closely related finch species on the Galapagos Islands near South America. Although very similar, they had differing characteristics such as their beaks which he later concluded were adaptations for what food was accessible on specific islands that they inhabited. (Web ref 1). On Darwin’s return home he tried to explain his findings and concluded that similar to the geology of rocks, biological organisms also changed through evolution and produced with the idea of ‘natural selection’.
Darwin spent years exploring this idea, and although genetics hadn’t been discovered at the time, his theory is based upon them. He published his idea of evolution in his most famous book ‘The Origin of Species’ (1859).
Darwin had realised that there must be changes in the characteristics of animals, plants and humans and that there was not a fixed nature that had come from a ‘creator’. (Trigg, R. 1999, P109).
Thomas Malthus (1766-1834), a clergyman and economist, produced the essay ‘The Principles of Population’ (1798), which described how the population of humans would double every 25 years unless restricted by food supplies. (Web ref 1). Darwin applied this to animals and plants and realised they too must be ‘kept in check by predators, diseases, and limitations in food, water, and other resources that are essential for survival.’ (ibid). Frogs and spiders for example produce a large number of offspring and there are many of them reproducing. The struggle to survive there for is not only dependent on resources and predators but on variability individual chances that give the advantage of passing on this to another generation.
On natural selection, Darwin says’ Owing to the struggle for life, any variation, however slight, and from whatever preceding, if it be any degree profitable to an individual species….will tend to the preservation of that individual, and will generally be inherited by its offspring.’ (Trigg, R. 1999. P109).
He therefore suggests that the change of individuals through evolution is because of the variation of characteristics each generation has. Individuals with the characteristics suiting the environment to help survival will have a higher opportunity to reproduce passing on these traits. For example, if the colour of a similar selection of insects in one environment is red or brown and the red species are more noticeable to predators, the brown insects are more likely to survive, increasing their chance to reproduce, passing on their variable characteristics and becoming the dominant population. Should the environment change to make the red less noticeable, the opposite then would occur.
This can be related to Darwin’s understanding of ‘The Survival of the Fittest’, he has been misinterpreted as meaning ‘the survival of the strongest’ individual or species. What he actually meant is ‘natural selection’, the survival of the individuals or species that fits best into its environment through variation of characteristics giving it the best opportunity to reproduce.
He also explains that these evolutionary changes do not just happen overnight, new species don’t just pop up or blend together into one as these changes are minute and gradual over time. (ibid)
Darwin’s Natural Selection in its simplest terms may be described as, ‘The animals (or plants) best suited to their environment that are more likely to survive and reproduce, passing on the characteristics which helped them survive to their offspring. Gradually, the species changes over time.’(Web ref 3)
Darwin’s ideas had obviously been formed and influenced by other theories and thoughts, his grandfather Erasmus Darwin (1731-1802). They shared similar ideas of evolution and the belief that life came from one common ancestor, Erasmus however, focused more on sexual selection and believed that evolution happened through dominant stronger males passing on their characteristics to offspring. In his book ‘Zoonomia’(1795) he adds ‘The final cause of this conflict amongst the males seems to be, that the strongest and most active animal should propagate the species, which should thence become improved’ (cited in The Essential Writings of Erasmus Darwin, King-Hele, D. 1968, pp85-86). Erasmus’ ideas were closer to that of Lamarck than his grandson’s.
Lamarck’s work, which had interested Darwin at University, had also proposed ideas of evolution. He believed that organisms passed on traits to their next generations too, but unlike Darwin, he concluded that these traits were acquired throughout their life time while adapting to the environment and passed onto their offspring. Of course Darwin’s theory suggested that the process of change was already there and passed on through survival. (Web ref 4).
A common example of Lamarck’s theory is of a giraffe. His idea would suggest that a giraffes stretches its neck to reach high leaves. The neck of the giraffe would therefore stretch because of it and the offspring would inherit this long neck. Darwin on the other hand would suggest a giraffe with a longer neck can reach higher food than others without. It is more likely to survive in the environment because of advantageous variables; they would be passed onto its offspring. (Web ref 5).
Herbert Spencer (1820-1903) was an English philosopher who originally used the term ‘survival of the fittest’ after reading Darwin’s work. He also dismissed the idea of creationism and wrote ‘Those who cavalierly reject the Theory of Evolution as not being adequately supported by facts, seem to forget that their own theory is supported by no facts at all’ (Web ref 6). He too, like Lamarck, believed that evolution was a result of usage of a characteristic and was passed on and if it wasn’t useful it would disappear.
Darwin did not invent the idea that animals plants and humans were the result of evolution, many psychologists, scientists and philosophers throughout history have helped shape the way we understand the dynamics of life on the planet, Charles Darwin was however the first who made his idea viable with an explanation that today can be backed up with genetics and obvious inheritable traits.