We often think of scientific ideas, such as Darwin’s theory of evolution, as fixed notions that are accepted as finished. In fact, Darwin’s On the Origin of Species evolved over the course of several editions he wrote, edited, and updated during his lifetime. The first English edition was approximately 150,000 words and the sixth is a much larger 190,000 words. In the changes are refinements and shifts in ideas â€” whether increasing the weight of a statement, adding details, or even a change in the idea itself.
The second edition, for instance, adds a notable â€œby the Creatorâ€ to the closing paragraph, giving greater attribution to a higher power. In another example, the phrase â€œsurvival of the fittestâ€ â€” usually considered central to the theory and often attributed to Darwin â€” instead came from British philosopher Herbert Spencer, and didn’t appear until the fifth edition of the text. Using the six editions as a guide, we can see the unfolding and clarification of Darwin’s ideas as he sought to further develop his theory during his lifetime.