Syllabus

CPSP118G Spring Semester: Earth, Life & Time Colloquium

Charles Darwin and the Discovery of Evolution

Thomas R. Holtz, Jr.

Charles Robert Darwin (1809-1882)

Childhood and Education:

The Voyage

Darwin's Professional Life

So, What Did Darwin & Wallace Discover?
Their model was called Natural Selection, and was analogous to "artificial selection" (e.g., domestication). Darwin and Wallace's observations:

Thus, IF some variation gives the individual a slight advantage (bigger, stronger, smaller, smarter, less tasty, whatever) at surviving; and IF that variation is heritable; THEN there is a somewhat better than average chance that organisms with that variation will survive to bear the next generation. Over the long expanse of geologic time, the accumulation of these variations will change the population from one form to another: the origin of species.

Hence,

* Natural Selection is the differential survival and reproduction of variants in a population resulting in a net change in phenotype of the descendants. *

(Short form: "Natural selection is the differential survival and reproduction of variants in a population.")

(Even shorter form with a 20th Century slant: MUTATION PROPOSES, SELECTION DISPOSES)

If Evolution can be summarized as "no one is identical to their parents", then Natural Selection can be summarized as "no one is identical to their siblings, either; plus, life's hard!"

Key points of Natural Selection:

"Survival of the Fittest"?: Not as such. Phrase not in the earlier editions of the Origin, nor was it coined by Darwin. Comes from economist/philosopher Herbert Spencer:

Some things Evolution and Natural Selection are NOT:

Scientific Reactions to Darwin and the Origin
In the late 19th Century, many parts of Darwin's work were accepted:

On the other hand, while some (Thomas Huxley, Joseph Hooker, O.C. Marsh, etc.) accepted Natural Selection, many others did not. In part they thought it could not create entirely new morphologies, but mostly because they accepted Lord Kelvin's incredible short (and inaccurate) time scale. With (for example) only 3 million years for all the Cenozoic Era, it would be hard for Natural Selection to produce the vast diversity of modern mammals.

Darwin died without knowing the mechanism by which variation was generated and passed on: genetics. (Trivia time: he actually had a copy of Mendel's work at his desk, but he had never gotten around to opening it!). Gregor Mendel's genetic work only became well-known and studied in the 20th Century. By the mid-20th Century, new discoveries in genetics, paleontology, ecology, and statistics led to the New Synthesis: a model demonstrating that Natural Selection is indeed a major force in evolution.

However, there is more to it than that. Stay tuned...

Last modified: 10 January 2008