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Introduction
Throughout history a number of alternate theories of evolution have been proposed by equally intelligent scientists, most notably the theories of Jean Baptiste Lamarck, Charles Darwin and Alfred Russel Wallace. As with various theories, many tend to raise the question as to which theory has had the greatest contribution to modern evolutionary theories. Evolution is the one of the fundamental keystones of modern biological theory, through which organisms gradually changes over an extended period of time in response to its environment and other factors.
Lamarck
Jean Baptiste Lamarck, built on the knowledge of his mentor Count George-Louis Leclerc de Buffon, to make what is credited as the first major advance towards modern evolutionary theory. Famously known for his Theory of Inheritance of Acquired Characteristics, first presented in 1801, Lamarck designed a two-part mechanism which described a how changed was introduced to species and then passed down through generations.
The first aspect of his theory of evolution was based around “how organisms (e.g. animals, plants) change during their lifetime, and then pass these changes onto their offspring.” An example frequently used was that of a giraffe. Lamarck believed that a giraffe’s neck grew longer throughout its lifetime to reach leaves in high trees. Lamarck believed that these changes were determined by what the organism needed or wanted to survive. As such, he believed that aspects of the body which aren’t in use, such as the human appendix and fifth toes will gradually disappear. He hypothesised that evolution is the result of a predetermined plan and that the future is already decided (New England Complex Systems Institute , 2019). The issue of this theory was that whilst Lamarck himself discussed it as a “natural tendency towards perfection” it was inexplicable as to how these changes occurred.
The additional aspect of Lamarck’s theory of evolution was referred to as ‘Lamarckian inheritance’. His belief was that organisms inherit the acquired traits of its ancestors. Using the giraffe as an example, Lamarck’s theory meant that if giraffes were to acquire long necks than its offspring would be born with a long neck as opposed to the short necks its parents were born with. This theory however, has also been disproven through the discovery of hereditary genetics which explains how particular characteristics are transmitted to an offspring by its parents.
Whilst Lamarck’s theory showed reason, it became clear that over time all organisms would become far too complicated and therefore the theory didn’t account for simple or single-celled organisms. Additionally, it can been observed that characteristics inherited throughout an individuals lifetime such as an ear piercing isn’t then passed onto their child at birth.Thus Lamarck’s theory was disproven and over time scientists looked for new evolutionary theories.
Darwin
An eighteenth-century English doctor named Erasmus Darwin found many different aspects of what is now known as evolutionary theories. It wasn’t however until his grandson, Charles Darwin published his infamous book, ‘on the origin of species’ that these theories became known as scientific . Charles Darwin’s theory of evolution was based on both Lamarckian ideals and fossil discoveries whereby he theorised how living species changed over time and all stemmed from an ancestral organism. This theory is often referred to as ‘natural selection’, whereby organisms possess different variations from one another which assist in their survival and reproduction.Once again using the giraffe as an example, Darwin’s theory suggests that the longer necked giraffes were more likely to survive and reproduce as they had access to the food on higher trees which the shorter necked giraffes couldn’t reach. As result more longer necked giraffes would survive as they are a better “fit” for the environment they live in. Thus, the term, “survival of the fittest” was introduced.
Throughout history Darwin’s theory has become the most accepted theory of evolution as it has the most substantial evidence supporting it. Even after his death, Darwin’s theory was strengthened through emerging genetic information which proved that inherited traits were indeed passed through genes, unaffected by the organisms’ physical traits and attributes. Consequently, the genetics proved that Darwin’s theory was more genetically and scientifically possible than that of Lamarck’s.
Wallace
Following Darwin’s theory of evolution, naturalist Alfred Russel Wallace supported and researched the evolutionary theory of natural selection. Best known for his study of warning colouration in animals and speciation Wallace worked all over the world gathering evidence which supported his in depth evolutionary theory. An example frequently associated with Wallace was his study of the Golden Birdwing Butterfly (Ornithoptera croesus) which he found whilst studying in Indonesia. It was through his observations of both the diversity of the birdwing species from geographically close islands, and the variety within individual birdwing species, that Wallace theorized how animals changed to suit their environment.
This was potentially Wallace’s greatest contribution to evolutionary theory of natural selection, as he not only established how animals are affected by their environment, but also how the environment can be defined by the organisms which reside there.
He learnt that many butterflies all over the world resemble the soil, leaves or patterns of environment they live in.Thus, creating protection in the form of camouflage from predators, assisting in their survival and allowing for more reproduction.
Modern theory
Since the late 19th century there have been an abundance of new and initiative discoveries to enhance the theories of Lamarck, Darwin and Wallace and create the theory of evolution known today. Consequently the 20th century modernised theory of evolution is a combination of the natural selection works of Darwin and Wallace, and the basic knowledge of genetic inheritance provided by scientist Gregor Mendel. Through time it has become clear that whilst all three scientist theories had merit, they lacked the genetic knowledge of Gregor Mendel. Mendel’s work is now in combination with the theories of Darwin and referred to as the “Neo-Darwinism”. The Neo-Darwin evolutionary theory incorporates all of modern understanding of concepts such as; population genetics, developmental biology, and palaeontology, as well as aspects of Darwinism such as natural selection and genetic variation. According to this new theory, evolution is driven primarily through chance. Chance mutations which affect one or multiple nucleotides of DNA per occurrence. Bigger ‘chances’ result in recombination, a genetic process which swaps, transfers or doubles
DNA creating new strands of DNA in the form of a mutation or recombination.
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