Kettlewell’s work was critically studied by Michael E.N. Majerus of the Department of Genetics at the University of Cambridge. In his publication, Melanism : evolution in action, (1998), Majerus found that Kettlewell’s was correct in stating that moth survival depended on its colour, "Differential bird predation of the typica and carbonaria forms, in habitats affected by industrial pollution to different degrees, is the primary influence on the evolution of melanism in the peppered moth." However, Majerus found that Kettlewell’s research was flawed as when testing how likely the moths were to be eaten; he placed the moths on tree trunks, a place where they would rarely rest in nature. Majerus also found that as birds see ultraviolet much better than a human can and therefore what may seem well-camouflaged to the human eye may not be to a bird. Although we know that the rise and fall of the carbonari is a persuasive example of natural selection in action, it is important to remain cautious about claiming that the sole reasons for this phenomenon are the camouflage of the moths and their visibility to birds.
Jean-Baptiste Lamarck (1744-1929), credited with making the first advance toward modern evolutionary theory, had a major influence on Darwin’s research. Lamarck’s theory, however, differs from his Darwin’s, as his theory is referred to as the theory of transformation or simple Lamarckism. Although in his lifetime he did not receive much recognition, today, Lamarck’s work is considered a major step forward. A classic example of Lamarckism is the elongated neck of the giraffe. According to Lamarck’s theory, a giraffe could, over a lifetime of straining to reach high branches, develop an elongated neck. Lamarck described this as a “natural tendency toward perfection”. Another example Lamarck used was the toes of water birds, he proposed that from years of straining their toes to swim through water, water birds gained elongated, webbed toes so they could swim with ease. Lamarck also believed that if a trait was not used it may become reduced. The winds of a penguin, for example, would be smaller than those of other birds as penguins do not use them to fly. Although these examples demonstrate how the use or disuse of a characteristic could change a trait, a major downfall of Lamarck’s theory is that he could not explain how this phenomenon may happen.
The indirect evidence for evolution is based primarily on the similarities found in different organisms, which are only explicable if they have derived from one single origin. An example of this can be found in the different species of flowering plants, there are millions of different types of these plants, but all of them share the same basic structure of roots, stem-bearing branches, leaves containing the green pigment chlorophyll and flowers. Although these plants differ in detail between different species, they are all built and live in the same way. The similarity of plan is easily explicable if all descended from a common ancestor. The term homologous is used to explain the structures formed in this way.
In vertebrate animals, the skeleton and forelimb are another example of homology. The bones of the upper arm, the forearm, wrist, hand and fingers in a human, can all be matched, bone to bone, to that of those in the rat, dog, horse bat and mole, porpoise and mole. This evidence is significant to the theory of evolution as it displays the way in which the bones have become modified in adaptation to different styles of life and also implies that this structure of bones has been inherited from a common ancestor. German embryologist Karl Ernst von Baer (1828) wrote “In my possession are two little embryos in spirit, whose names I omitted to attach, and at the present I am quite unable to say to what class they belong. They may be lizards or small birds, or very young mammals, so complete is the similarity in the mode of formation of the head and trunk in these animals.” Darwin believed that the embryonic similarity was due to the inheritance of the structure from the embryo of a common ancestor.
The study of palaeontology provides key evidence supporting evolution; the fossils in the earths crust are objective evidence of the course taken by living organisms in their evolutionary history. Fossils themselves to not “prove” evolution, it had been argued by Georges Cuvier in his essays that they had all been created specially and then succumbed to catastrophes. However, a view such as Cuvier’s fails to explain why the fossil forms studied fall in such an obvious series, nor does it explain why the teeth, feet and body sizes of fossil horses are so closely correlated with their different climatic conditions of their environments.
Darwin’s theory of evolution would predict that individuals would become selfish, as this would improve an individuals survival and potential reproductive success. Wynne-Edwards (1962) conducted research into group selection, and found that animals do not gain a selective advantage by behaving in such a way that the group of species benefits. A group comprising these organisms would be open to exploitation by other selfish animals. There are situation, however, where altruistic behaviour would be beneficial to the inclusive fitness of the species. In these situations, natural selection would favour such behaviours. Hamilton (1964) believed that if the individuals receiving the benefits are close relatives, they will share a large proportion of their genes with the donor, a high coefficient of relationship. Therefore, if the altruistic act allows the recipients to have more offspring, the donor will have at least some of their own genes passed on. This implies that natural selection operates on a genetic level, as opposed to a group or individual level. Trivers (1971) found that sometimes, unrelated animals may show signs of altruism towards each other. This behaviour is adaptive as long as the behaviour is reciprocated, the benefit of the recipient must be greater than the cost to the donor for this behaviour to evolve.
There are several aspects of human psychology which make homo-sapiens stand apart form other animals. The human intellectual capacity, the overall brain size of a human imply a greater capacity to process information having been arguably the most dominant psychological characteristic selected for during the evolution of the human species. The capacity for emotion and effect sets human beings apart form other animals as humans are susceptible to experience great heights of ecstasy and depths of depressed. Compared to other animals, humans are more likely to have excesses of joy (e.g. manic depression) and excesses of sadness (e.g., unipolar depression. No other animals are known to intentionally kill themselves. Humans are the only known animals to exhibit such destructive tendencies towards their surrounding environment and fellow members of their species. On the other hand, however, humans also display some remarkably altruistic behaviour, which may not seem particularly adaptive.
References
Baer, Karl Ernst von. 1928, Über Entwickelungsgeschichte der Thiere. Beobachtung und Reflexion. 2 vols. in 1. Königsberg: Gebrüder Kornträger
Darwin, C. (1888). The Origin of Species by Means of Natural Selection, or, The Preservation of Favoured Races in the Struggle for Life. London, John Murray.
Eiseley, L. 1958. Darwin's Century: Evolution and the Men who Discovered It. Doubleday, New York.
Karl Ernst von Baer: (1792-1876) On the 200th birthday of the "father of embryology". Dtsch Med Wochenschr. 1992 Dec 22;117(51-52):1976-9. German. PMID: 1478173; UI: 93121886.
Kettlewell, H.B.D. 1973. The Evolution of Melanism. Oxford University Press, Oxford.
Martin J. S. Rudwick, Georges Cuvier, Fossil Bones, and Geological Catastrophes (Chicago: University of Chicago Press, 1997).
Majerus, M.E.N, Melanism - Evolution in Action, Oxford University Press, New York, (1998)
Packard, A.S. 1901. Lamarck, the Founder of Evolution: His Life and Work. Longmans, Green, and Co., New York.
Smith, J.C. 1993. Georges Cuvier: An Annotated Bibliography of his Published Works. Smithsonian Institution Press, Washington DC.
Wynne-Edwards, V.C., 1986. . Oxford: Blackwell.
