INTRODUCTION: THE NATURE OF SCIENCE AND BIOLOGY
Medicine
Pharmaceutical
Biochemical
Medical-scienceDarwinian evolution | Back to Top

Charles Darwin, former divinity student and former Medical student, secured (through the intercession of his geology professor) an unpaid position as ship's naturalist on the British exploratory vessel H.M.S. Beagle. The voyage would provide Darwin a unique opportunity to study adaptation and gather a great deal of proof he would later incorporate into his theory of evolution. On his return to England in 1836, Darwin began (with the assistance of numerous specialists) to catalog his collections and ponder the seeming "fit" of organisms to their mode of existence. He eventually settled on four main points of a radical new hypothesis:

1. Adaptation: all organisms adapt to their environments.
2. Variation: all organisms are variable in their traits.
3. Over-reproduction: all organisms tend to reproduce beyond their environment's capacity to support them (this is based on the work of Thomas Malthus, who studied how populations of organisms tended to grow geometrically until they encountered a limit on their population size).
4. Since not all organisms are equally well adapted to their environment, some will survive and reproduce better than others -- this is known as natural selection. Sometimes this is also referred to as "survival of the fittest". In reality this merely deals with the reproductive success of the organisms, not solely their relative strength or speed.

Figure 4. Charles Darwin (right) and Alfred Wallace (left), the co-developers of the theory of evolution by means of natural selection. Image of Charles Darwin from http://zebu.uoregon.edu/~js/glossary/darwinism.html.Image of A.R. Wallace (right) is modified from http://www.prs.k12.nj.us/schools/phs/science_Dept/APBio/Natural_Selection.html.

Unlike the upper-class Darwin, Alfred Russel Wallace (1823-1913) came from a different social class. Wallace spent many years in South America, publishing salvaged notes in Travels on the Amazon and Rio Negro in 1853. In 1854, Wallace left England to study the natural history of Indonesia, where he contracted malaria. During a fever Wallace managed to write down his ideas on natural selection.

In 1858, Darwin received a letter from Wallace, in which Darwin's as-yet-unpublished theory of evolution and adaptation was precisely detailed. Darwin arranged for Wallace's letter to be read at a scientific meeting, along with a synopsis of his own ideas. To be correct, we need to mention that both Darwin and Wallace developed the theory, although Darwin's major work was not published until 1859 (the book On the Origin of Species by Means of Natural Selection, considered by many as one of the most influential books written [follow the hyperlink to view an online version]). While there have been some changes to the theory since 1859, most notably the incorporation of genetics and DNA into what is termed the "Modern Synthesis" during the 1940's, most scientists today acknowledge evolution as the guiding theory for modern biology.

Recent revisions of biology curricula stressed the need for underlying themes. Evolution serves as such a universal theme. An excellent site devoted to Darwin's thoughts and work is available by clicking here. At that same site is a timeline showing many of the events mentioned above in their historical contexts.