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Thanks I am no expert on Darwin’s ideas. My understanding is that he thought that one member of a species would have a chance mutation and that this mutation would give this member a better chance at survival and reproduction. The offspring of this member would then become isolated and the advantageous trait would become dominate in the species. This process of change would continue until breeding became impossible with members of the “old” species and that would signal the emergence of a new species.
Gradualism, geometric v. exponential growth, inheritance of acquired characters are the building blocks that Darwin used to build his theory. But what interests me the most is why he came up with the scenario that he did. Other scenarios are possible using these same observations. Did the Victorian industrial culture influence the way he saw nature?