Information taken from: Thread of Life: The Smithsonian Looks at Evolution by Roger Lewin. New York: Norton, 1982.

Archbishop James Ussher, in the 17th century calculated the precise date of the Creation: 4004 B.C.

But the discovery of the petrified remains of creatures that no longer existed demanded a different, more complex explanation. The diluvial theory was advanced, accounting for fossils as the victims of Noah's Flood. But it became evident that the rocks contained not one population of animals that had apparently been wiped out, but successive groups, each clearly related to the next through time, but each distinctly different. The cataclysmic theory was advanced which held that the great physical features of the world were sculpted in instantaneous paroxysmal events.  

Sir Charles Lyell presented the case for gradual geological change.

When Darwin boarded the H.M.S. Beagle in 1831, he saw the world through Lyell's eyes. In the archipelagos off the coast of South America, he wrote, "the most remarkable feature in the natural history of this archipelago is that the different islands to a considerable extent are inhabited by a different set of beings."

Origin of Species did not appear until his 50th year, in 1859. Evolution, or transmutation of the species, was how he originally thought of it.

He knew that every species has the potential to produce more offspring than will eventually survive. So, he reasoned, there must be a struggle for survival. It is these individuals that will preferentially survive, and they will pass their special attributes on to their offspring. "This preservation of favorable variations and the rejection of injurious variations, I call Natural Selection."

Darwin's theory replaced the notion of progression and improvement through successive creations, by the simple concept of change, a constant adaptation to local conditions. From time to time species become extinct and new species arise from existing ones. The new species are not "higher" in any sense than extinct ones, just suitably adapted to prevailing conditions.

Connectedness: "All organic beings that have ever lived on this Earth have descended from some one primordial form, into which life was first breathed."

Two major criticisms of the Origin in Darwin's time: The first concerned the physical source of variations. Darwin knew that variation occurred and that in general it was heritable. But he had no idea of how the phenomenon might be explained. The second was that the Earth wasn't old enough according to nineteenth century speculations.

Herbert Spencer recruited the theory of natural selection to describe and model Victorian society under the phrase "Social Darwinism."

Darwin was comfortable with the notion of a shared ancestry with the apes (not descended from) even though almost no fossil human ancestors had been found. Darwin predicted the Out of Africa theory: "In each great region of the world the living mammals are closely related to the extinct species of the same region. It is, therefore, probable that Africa was formerly inhabited by extinct apes closely allied to the gorilla and chimpanzee; and as these two species are now man's nearest allies, it is somewhat more probable that our early progenitors lived on the African continent than elsewhere."