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For several years in the 1990s I gave tutorials on Darwin and evolution in support of Peter Bowler's history of science course in Belfast, but I had never actually read the book that started it all. My recommendation to the casual reader would be to skip about half of it. Darwin basically has three startling ideas here, and the chapters where he talks about them are excellent, almost exciting, as he modestly challenges the received wisdom of the day. He wanders off topic, though, into areas like hybridism and geographical distribution, and I found those chapters much tougher going.

Darwin's three ideas are these:
  1. Most fundamentally, that it is possible to come up with a scientific explanation of how species change. (This is actually the second argument in the book, but it is the most important.) Although most of the book is a massing of evidence in favour,he takes one or two moments to tilt against any idea that species originate through acts of supernatural creation. "To admit this view is, as it seems to me, to reject a real for an unreal, or at least for an unknown ,cause.  It makes the works of God a mere mockery and deception; I would almost as soon believe with the old and ignorant cosmogonists, that fossil shells had never lived, but had been created in stone so as to mock the shells now living on the sea-shore."
  2. Darwin works up to this gradually, reviewing in considerable detail how humans change domesticated species of both animals and plants through artificial selection. He is not in general as lucid a writer as Gould, or even Dawkins. But the first four chapters on their own set out a compelling case that the answer to the question posed by the book's title is that species generally originate by descent from other species with modification by natural selection. (The word "evolution" is not used.)
  3. The third new element introduced by Darwin is the enormity of geological time. Having proposed a very slow process of change, he needs long ages to have passed for it to operate. This also helps him with another difficulty - he needs the fossil record to be incomplete in order to account for the fact that we don't find many intermediate stages of species change (though there are other factors here). He is coy about the details but does propose that the Weald has taken 300 million years to erode to its present situation. I think today's estimate is more like 100 million years, but he's within an order of magnitude.
We are still hazy about some of the details on all of this - in particular, the development of genetics has bolstered the general argument while muddying some of the details. But basically Darwin was right on all three of his big ideas, and on all three of them he was challenging received wisdom - though of course he was not alone, and in an appendix lists other writers who had come to similar conclusions in recent years

It is worthing also noting what Darwin doesn't do. He doesn't use the word "evolution"; he says little about God and nothing about the Bible; he has precisely one sentence about the relevance of this to humanity, saying that as a result of his book, "Light will be thrown on the origin of man and his history." But the implications are pretty clear.

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Comments

( 3 comments — Leave a comment )
sashajwolf
Jan. 10th, 2010 08:37 pm (UTC)
The third new element introduced by Darwin is the enormity of geological time.

Surely he got that from James Hutton, via Lyell, whose books he had read? Hutton famously wrote of the history of the earth, "We find no vestige of a beginning - no prospect of an end." He also had some insight into the principle of natural selection, although he seems to have thought it operated only to produce new races within species, rather than being responsible for speciation itself.
gareth_rees
Jan. 11th, 2010 02:09 am (UTC)
he has precisely one sentence about the relevance of this to humanity

To make up for that, he did write another book (partly) about that subject. Remember that he was under some time pressure with Origin (e.g. lack of proper references).
nickbarnes
Jan. 11th, 2010 10:35 am (UTC)
As I understand it, "evolution", at the time, had a teleological sense: it could be taken to mean the literal "unfolding" of a hidden, existing, design. This meaning is contrary to Darwin's idea.

Many people, for many years, had observed changing forms in the fossil record, and had applied the word "evolution" to it.

Gould - unsurprisingly - has quite a good essay on the pre-Darwinian uses of the word.
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