On November 24, 1859, Charles Darwin's On the Origin of Species was published, changing the way we look at life on our planet.
Our library database Access Science contains a concise biography of Darwin in which the origin of On the Origin of Species is described, beginning with Darwin's scientific work aboard the HMS Beagle, the ship on which he traveled for almost five years:
"Before the voyage of the Beagle Darwin, like everyone else at that time, did not believe in the mutability of species. But in South America he saw fossil remains of giant sloths and other animals now extinct, and on the Galapagos Islands found a colony of finches that he could divide into at least 14 similar species, none of which existed on the mainland. It was obvious to him that one type must have evolved into many others, but how they did so eluded him. Two years after his return he read Malthus's An Essay on the Principle of Population (1798), which proposed that the human population is growing too fast for it to be adequately fed, and that something would have to happen to reduce it, such as war or natural disaster. This work inspired Darwin to see that the same principle could be applied to animal populations and he theorized that variations of a species that survive (while other members of the species do not) pass on the changed characteristic to their offspring. A new species is thereby developed which is fitter to survive in its environment than was the original species from which it evolved."
Here is a passage from The Origin in which Darwin describes the process of natural selection:
"It may be said that natural selection is daily and hourly scrutinising, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life."
You can read Darwin's published works, including On the Origin of Species, at darwin-online.org. UMUC library databases contain scholarly and popular articles about him, such as these articles in Academic Search Complete.
Happy birthday, Origin!
[Photo of Darwin from http://darwin-online.org.uk/]