"I am almost convinced (quite contrary to opinion I started with) that species are not (it is like confessing a...

"I am almost convinced (quite contrary to opinion I started with) that species are not (it is like confessing a murder) immutable."

The birth of the Theory of Natural Selection, in a letter.
Eight years after returning from his globe-spanning voyage aboard the Beagle, Charles Darwin penned this letter to Joseph Dalton Hooker. Darwin had spent years analyzing the botanical and animal specimens he collected from the Galapagos. He had noted their variations, their geographical relationships, and his theory of how species arise was beginning to take shape. And he was nervous about telling the world.

Their correspondence has been digitally archived by the University of Cambridge library, and it’s a time capsule to the moment when the most important principle in all of biology was hatched from the noggin of one British naturalist named Darwin. It’s hours of fun, give it a read here http://cudl.lib.cam.ac.uk/collections/darwinhooker