BEFORE DARWIN
Before Charles Darwin formulated his theory of evolution, there appears to be many theories existing at the time.
From ancient times, there were scientists such as Aristotle who classified organisms with similar characteristics with one another into what is called genera before dividing the organism in each genera into different species. Following his lead, there were others such as John Ray who proposed that the organisms on Earth could be examined to determine the creation, association and the destiny of the Earth which is ultimately decided by God.
After these scientists, there were many others who seek to provide an explanation for the origin of life. In the 18th century, Georges-Louis Leclerc, Comte de Buffon observed that Man had many characteristics in common with the apes and even proposed that we could have descended from a common ancestor. He did not, however, provide an acceptable explanation for this idea. At this same time, Carl Linnaeus proposed the Linnaean classification in which animals are ranked in a type of hierarchical classification. This classification is still being used in today’s society. Erasmus Darwin, grandfather to Charles Darwin, had in his grandson’s words anticipated Lamarck’s theory at this point of time in the history of evolutionary thought.
The main theory before natural selection would be that proposed by Jean-Baptise Pierre Antoine de Monet, Chevalier de Lamarck. Lamarck formulated the theory of inheritance of acquired traits in which he points out that organisms would pass on the traits they have acquired within their lifespan to their offsprings. Lamarck built his theory based on two observations he made, mainly using the giraffe as an example to support his theory. The two observations are as follows:
1. Use and Disuse
2. Inheritance of Acquired Traits
Lamarck observed that organisms will eventually lose the characteristics which they do not have a need for or which they do not use and will develop the traits which will be useful for their survival. He uses the giraffe as an example to support this. Lamarck states that giraffes require the trait of having long necks as they have to reach for the leaves in the trees, thus their necks would strengthen and lengthen after a period of time. Also, Lamarck states that all organisms would inherit their traits from their ancestors. Thus the giraffes would pass on the traits they have acquired to their offspring resulting in the development of slightly longer necks in the next generation.
With this in mind, Lamarck developed two laws for his theory:
1. In every organism which has not hit its limit for development, the often and continuous use of a particular organ would slowly strengthen and develop it and the disuse of an organ permanently will result in its weakening until it stops functioning. This organ will then cease to exist in the organism.
2. All acquisitions and losses of characteristics, due to the changes in the environment, of an organism will be passed on through reproduction to its offspring, given the condition that the acquired changes in traits are applicable to both sexes, or at least to the individuals which produce the offspring.
Alongside Lamarck, Thomas Malthus had observed that there was an overproduction of offspring in organisms and that this would eventually lead to competition for the limited amount of resources found here on Earth. This was what eventually paved the way for Darwin’s proposal of his theory on natural selection.
Before Darwin proposed his theory on natural selection, there was one other scientist who had a theory similar to that of Darwin. Through the study of trees, Patrick Matthew observed that trees were different from one to another and was able to derive a theory of natural selection which was not as fully developed as that of Darwin’s.
DURING DARWIN
Along with Darwin who formulated the theory of evolution through natural selection, there was one other person who formulated a theory strikingly similar to it. This person would be known as Alfred Russel Wallace and he proposed the theory that natural selection is an environmental weeding out process of those which could not adapt. This is where his theory would differ from that of Darwin who theorized that competition for the limited resources is the genuine weeding out process.
He travelled and collected plant samples in the Amazon basin together with Henry Walter Bates (1842-52) and was similarly employed in the Malay Archipelago and the Spice Islands (1854-62).
Wallace theorized on the basis of his findings and was influenced by Thomas Malthus' Essay on Population. These later allowed him to propound a theory of the evolutionary origin of species by natural selection.
In 1858, Wallace sent an essay he had written to Darwin - On the Tendency of Varieties to depart indifenitely from the Original Type. It is this that prompted Darwin to make known his findings on natural selection.
Also, Darwin was very much influenced by the geologist Charles Lyell. Lyell proposed a theory very much different from all the prevailing theories of geology at the time. According to him, the theories at the time were prejudiced, being based on the interpretation of Genesis. He thought that we should exclude sudden geological catastrophes to account for fossil remains of extinct species and believed it was necessary to know that Earth’s history went back a long way. This concept was called Uniformitarianism.
Lyell stated that the origin of human species was far beyond the prevailing theories of that time, that the origin of the human species went a very long way back.
All these eventually led Darwin to construct his theory of evolution based on natural selection and make it known to the public.
RELIGIOUS CONTEXT
At the time, there was the interpretation of the Book of Genesis in which God had created the world as how it is now and the distinguishable living organisms along with it. People at the time, mainly Christians, believed that the world was as God had created it with no changes, meaning that there were no extinct species as well as no new species. It was extremely dangerous for Darwin to even begin to suggest that the human species was evolved from the apes.
However, the response to the publication of his book appeared to be of less ferocity as he had anticipated.
This theory proposed by Darwin, however is widely accepted today.
Sources:
http://en.wikipedia.org/wiki/Jean-Baptiste_Lamarck
http://www.ucmp.berkeley.edu/history/evothought
Evon
