Evolution

The Story of the Discovery of the Evolutionary Process of Life.

Cast of Characters:

Erasmus Darwin. Charles' grandfather, he wrote a book called Zoonomia in which he discusses his own theory of evolution which anticipated some of the theories of Lamark.

Jean Baptiste Pierre Antoine de Lamark. French naturalist who advocated a theory of evolution by "acquired traits". He felt that, over the generations, excessive demands or stresses made upon physical attributes of an organism, in trying to do a task, made that attribute more suited for the task and the improved attribute was passed on the offspring. Thus giraffes by trying to stretch their necks to reach food high in the trees would stress their necks and later generations would therefore have longer necks. This theory, though a good attempt to explain the various species spread over the surface of the earth, had many problems and does not match the scientific evidence.

Charles Lyell. Scottish scientist who developed the theory of uniformitarianism. The theory states that changes in the geology of the earth are due to natural processes that have operated in the past at gradual rates. Darwin was given a copy of Lyell's Principles of Geology by a friend to take with him on his voyage on the Beagle. Lyell postulated a much greater age of the earth than the 6000 or so years then accepted by Christian believers.

Thomas Malthus.He wrote a book (referred to by Darwin) in which he pointed out that while the human population increased exponentially, the amount of food that was available was limited. He predicted periods of great starvation and that the population of the earth is ultimately limited by the amount of available food. (The mathematics of his argument are still quite valid and apply to other resources besides food, such as water, energy, living space,...)

Alfred Russel Wallace.Co-discoverer (along with Darwin) of the Evolutionary Process. He was a young naturalist who sent a letter to Darwin which contained, in outline form, Darwin's own theory. By this time Darwin had been considering the theory for some 20 years. The letter led to a co-authored paper presented before the Royal Society which announced the details of the theory of evolution.

Charles Robert Darwin. Co-discoverer (along with Wallace) of the Evolutionary Process. Darwin began in 1830 to consider the variety of species on the earth and eventually discovered the process by which one species evolves into another species. This discovery explained the process by which ancient species evolved into the vast number of different organisms presently inhabiting the earth.
He was hired as ship's naturalist in 1831 aboard the HMS Beagle, an English survey ship. On the voyage, which lasted some 5 years, he collected a wealth of specimens and a wealth of observations that led him to his theory.

Darwin's reasoning.

• Limited Resources.
  The resources the organisms need to survive are limited. Resources such as food and space can only support a certain number of individuals.
• Variety.
  Within a given species there is variety. Two individuals are generally different. Many of these variations are inherited and are passed down to progeny.
• Some individuals are more successful at reproducing than others.
  Various factors are responsible for this:
  • The ability to obtain food.
  • The number of offspring that are produced.
  • The success at finding a mate.
  • The ability of live long enough to be able to reproduce.
• The traits of successful organisms are passed on to their offspring.
  Some of the traits which allowed an organism to succeed in producing offspring are passed on to the offspring. (i. e. those traits that are genetically determined.)
• Natural Selection.
  Among individuals who are competing for the same resources, those who have traits that better equip them obtain these resources are more likely to survive and have offspring. This is often called "Survival of the Fittest".

Some facts.

• Species have the potential to increase exponentially in numbers.
• The earth is immensely old.
• Beeders are unable to change the traits of an organism by affecting the environment or trying to modify the organism. -And, occasional "sports" with unusual traits appear, sometimes these traits "breed true".
• Organisms are similar in structure (homological).

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