17B+-+History+of+Evolutionary+Thought

Where did the idea of Evolution come from?
[|The History of Evolutionary Thought]is an interesting read. Click on the link to learn more.

There are many key thinkers that contributed to the evolutionary theory. We will mainly be focusing on Charles Darwin, Jean Baptiste Lamarck & Alfred Russel Wallace.

Key Thinkers in the evolutionary theory

 * During the first half of the 19th century it became quite obvious, that the organization, behaviour and occurrence of plants and animals is shaped by the environment.
 * It was also realized that the surface of the earth is constantly changing.
 * The English geologist CHARLES LYELL(1797 – 1875) drew a picture of the genesis of the earth
 * Charles Lyell published “Principles of  Geology”  in 1830
 * He explained the origin of layers by  subsequent depositions and the  development of rocks by pressure and  plication. LYELL’s ideas had a lasting  effect on DARWIN
 * The [|French zoologist G. L. BUFFON] (1707 – 1788) pointed out in his work ‘About the common descent from ancestors’ that not only donkey and horse, but human and monkey, too, belong to a natural family.
 * Idea was taken up by his pupil **JEAN BAPTISTE de LAMARCK** (1744 – 1829), who strengthened it in his work ‘Philosophie Zoologique’ published in 1809.
 * ‘Since every species has to exist in perfect harmony  with its surrounding and since this surrounding is  constantly changing, the species itself, too, has to  change constantly, if it is to stay in a harmonic balance  with its surrounding. If it would not adjust, the species  would be threatened by extinction.’
 * LAMARCK did thus discover the **TIME** factor  in the evolution of organisms.
 * In 1801, he coined the term biology.

Evolution Mechanism by Lamarck
How did the giraffe get its long neck? This question has puzzled biologists as far back as the early 18th century naturalist Jean-Baptiste Lamarck, who famously - and wrongly - speculated that the giraffe's ancestors had stretched their necks in search of food and passed this "acquired characteristic" onto their offspring.

The giraffe fossil record is fairly good, with a wide variety of species known from the Miocene. These sported a range of weirdly shaped horns, but all had short necks rather like that of the only other living species of giraffid, the okapi. Only in the late Miocene do we see the fossils of long-necked giraffes. Like modern giraffes, they have an extra vertebra in the neck - recruited from the back - and lengthened neck vertebrae.

Until recently, there was no fossil evidence linking the long-necked giraffes to their short-necked relatives. Recent news emerged that Nikos Solounias of the New York Institute of Technology had described a fossil giraffe from the late Miocene and early Pliocene. Its neck is a perfect intermediate between the short-neck ancestors and their long-neck descendants.
 * Lamarck used giraffes as an example to show evolution process. As the trees grew taller in the African  savannah, the leaves and fruits became out of reach
 * The giraffes stretched their necks to reach for the leaves, and this active use of the necks resulted in the enlargement and lengthening of the necks
 * The giraffes passed on these acquired genes to the next generation, which continued to “grow” their necks
 * This ultimately resulted in giraffes with long necks

Macroconcept: Evolution

 * 1) Change occurs with time
 * 2) For each evolutionary process, there are identifiable rules that govern the process of change. These rules depend on the fundamental nature of the evolving system.
 * 3) The form that the present takes depends directly on the possibilities inherent in the form of the past; some types of change are more likely than others. In addition, the nature of the past can sometimes be discerned from the nature of the present.

How the Theory of Evolution was formed

 * DARWIN was influenced by the ideas of the English economist THOMAS ROBERT MALTHUS (1766 – 1834).
 * In 1838 Darwin read "An essay on the principle of population, as it affects the future improvement of society"
 * It pointed out the problem of a population explosion due to the difference between exponential growth of the human species and linear growth of food production.
 * He foresaw the overpopulation of the earth as  a result of its limited capacity.
 * MALTHUS saw clearly that the limited  resources of the earth would cause a struggle  for existence.
 * From this Darwin concluded that competition exists  among all living things and a  "struggle for existence" might be the means by  which well adapted individuals survive and the  ill adjusted are eliminated


 * **Alfred Russel WALLACE** was a naturalist working mostly in the Malay Archipelago. He had also read Essay on the principle of population by Malthus and it came into his mind during a malarial fever.
 * He wrote..."suddenly there flashed upon me  the idea of survival of the fittest".
 * WALLACE had studied the distribution of animal species and concluded that  both a selection and an evolution  had to have taken place.
 * This conclusion was influenced  by the ideas of MALTHUS.


 * In 1858, while Darwin was working on his manuscript outlining his theory of evolution, he received a manuscript for review by a young English naturalist named Wallace.
 * The title was "On the tendencies of varieties to depart indefinitely from the original type". To Darwin's surprise Wallace had independently come up with the same theory of natural selection!
 * Darwin wanted to let Wallace publish first but Lyell convinced him that they should jointly present their work.
 * Papers by both Darwin and Wallace were read before the Linnaean Society of London on July 1, 1858. (http://wallacefund.info/the-1858-darwin-wallace-paper)
 * H. Lyell urged Darwin to publish his full theory of evolution as soon as possible.
 * "On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life" was published and sold out on Nov. 24, 1859.
 * Like Darwin, Wallace is very fond of beetles.
 * He actually visited Singapore, Bukit Timah Hill where he stayed for 2 months
 * Found 700 new species of beetles during his stay