The Evolution of Evolution

The H.M.S. Beagle made a routine landfall at the Galapagos Islands in 1835, to collect tortoise meat for the voyage. This fortuitous stopover lured Charles Darwin, the ship’s naturalist, into a lifetime of research, and into publishing the most controversial book ever written.

Darwin is often given sole credit for the theory of evolution by natural selection, but in fact several scientists laid the groundwork. Their research and theories helped him to form his own ideas about how evolution occurred. In addition to his own observations, Darwin’s theories were shaped by the ideas of Linnaeus, Cuvier, Malthus, Lamarck, and Lyell, to name but a few.

During the early part of the 1700’s, Carl Linnaeus founded the hierarchical system of classification. He classified all known creatures into biological categories; providing evidence of the relatedness between lifeforms. He placed man with apes, lemurs and bats in the order of Primates, and subdivided man into four groups according to skin colour and other characteristics. Darwin was intrigued by the fact “that the hand of a man formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat, should all be constructed on the same pattern, and should include the same bones in the same relative positions”! Darwin wondered if there was some kind of relationship between species, based on more than just a resemblance.

In the latter part of the 1700’s, Georges Cuvier founded paleontology. He described the differences between the fossil flora and fauna found in the distinct strata of rocks. He observed that the more recent the strata, the more closely the fossils resembled existing organisms. This prompted Darwin to speculate that new forms came into being during the Earth’s history.

Thomas Malthus published Essay on the Principle of Population in 1798. In his book, Malthus stated that if a population were to increase unchecked, it would double itself every twenty-five years, increasing by geometrical progression. He predicted that the population would increase beyond the availability of resources, such as food, air and water, and as a result there would be a fierce struggle for existence. Darwin thought that this principle must hold true for other forms of life too. He realized that natural selection; the struggle for existence, was the driving force for adaptations, and the evolution of life forms. Malthus had provided the central theory for Darwin’s work.

Jean Baptiste de Lamarck had a theory of evolution which he published in 1809. He deduced that individual animals change in response to different environments. He allied himself with the idea that these changes would then be passed on to offspring. Initially, Darwin modeled his process of evolution based on Lamarckian inheritance of acquired characteristics. Later, although Darwin never understood how heritable changes occurred, he discarded Lamarck’s theory of acquired characteristics. Darwin’s theory of evolution did however support Lamarck’s belief that species changed because of environmental factors.

In 1830, Sir Charles Lyell, a geologist, published a book that had an enormous influence on Darwin. The book’s main thesis was that past changes in the earth’s surface could be explained by the gradual operation of causes still at work. Darwin read this book during his exploration of South America and hypothesized that these slow, subtle changes over prolonged periods of time must apply to lifeforms too. If the earth had undergone such colossal transformations, then wouldn’t living things have had to adjust too, in order to adapt to the changing environment? Darwin always emphasized his debt to Lyell, in fact he considered offering him half the credit for The Origin of Species. Interestingly, Lyell never accepted Darwin’s theory of evolution, primarily because he could not identify any currently acting “force” that would be powerful enough to bring about evolution.

Charles Darwin’s five year voyage on the Beagle ended in 1936. He spent the next twenty years collecting facts and performing experiments to test his theory of evolution. By 1844 he had convinced himself of the theory of evolution, but he continued to work diligently, year after year, to gain more irrefutable evidence of his theory. In 1856, Lyell appealed to Darwin to publish his research results; Darwin procrastinated, he was still not satisfied that he could provide indisputable, comprehensive proof of his theory. Darwin might not have ever finished his work on evolution, had it not been for a letter he received in June of 1858.

The letter was from another English naturalist, Alfred Russell Wallace. Wallace was aware that Darwin was interested in evolution, and he sent a summary of his own theory. Darwin was amazed. Independently, both he and Wallace had formulated the theory of evolution by natural selection. In July of 1858, friends of Darwin arranged to present Wallace’s paper and an abstract of Darwin’s theory, written in 1844, to the Linnaean Society. Then Wallace generously agreed that Darwin, who had gathered far more evidence to support their joint theory, should continue with the idea, while he stepped aside.

Darwin quickly finished his controversial book called “On the Origin of Species”, and had it published in November of 1859. The book’s publisher realized that book would cause public outcry, and decided to print only 1,250 copies. The book sold out on the first day of publication. It has since undergone numerous reprintings, and it is still being reprinted now, over a century later.

Questions for the reader:

1. What preconceptions of the eighteenth and nineteenth centuries may have led scientists to overlook the pattern the Darwin eventually saw?

2. What role did empirical knowlege play in Darwin’s theory of evolution and

in recent scientific discoveries, with respect to heredity?

3. Darwin employed the analogy of artificial selection to illustrate his theories of

natural and sexual selection. Is this a case of inductive or deductive

reasoning? Why?

4. How might Darwin have tested and eventually rejected such theories as

Lamarck’s individual production of adaptions, and the inheritance of acquired

characters?

References:

Asimov, Isaac. (1982). Asimov’s Biographical Encyclopedia of Science and

Technology. New York: Doubleday & Company, Inc.

Bajema, Carl J. (1985, April). Charles Darwin and Selection as a Cause of

Adaptive Evolution 1837-1859. The American Biology Teacher. (Volume

47, No. 4, pp. 226-231.

Bynum, W.F., Browne, E.J., & Porter, Roy. (Eds). (1981). Dictionary of the

History of Science. (pp. 131-133). New Jersey: Princeton University Press.

Dampier, William. (1961). History of Science: and its Relations with Philosophy

& Religion. New York:; Cambridge University Press.

Faber Doris, & Faber, Harold. (1991). Nature and the Environment: Great Lives

New York: Charles Scribner’s Sons.

Miller, Jonathan, & Van Loon, Borin. (1982). Darwin for Beginners. New York:

Pantheon Books.

Parker, Steve. (1992). Charles Darwin and Evolution. London: HarperCollins

Publishers.

The Victorian Web. (2001/11/12). Darwin and Evolution. Available on-line at:

http://65.107.211.206/darwin/darwin5.html

The Victorian Web. (2001/11/12). Darwin and Evolution Timeline. Available

on-line at: http://65.107.211.206/darwin/darwin4.html

Youngson, Robert. (1998). Scientific Blunders: A brief history of how wrong

scientists can sometimes be. New York: Carroll & Graf Publishers, Inc.

Created by Vickie Harley