Early Evolutionary Ideas and Darwin's Insight

Chapter Summary

1. Critical changes that set the stage for Darwin and Wallace to come up with their ideas on evolutionary change and natural selection included the shift from supernatural to natural explanations, the move from catastrophism to uniformitarianism, the use of logic and pure reason, the acceptance that the world—both the biotic and abiotic world—was constantly changing, and the rejection of the idea that life formed by spontaneous generation.
2. Scientists sought mechanistic rather than supernatural explanations for the features of the physical world; they valued experimentation, data gathering, and hypothesis testing.
3. Lyell’s ideas in geology created a sense of deep time, Robert Chambers proposed that new species arose from existing species, Jean-Baptiste Lamarck hypothesized generational adaptations to environmental needs, and Patrick Matthew presented a preliminary theory of natural selection.
4. Darwin prepared his readers for his revolutionary ideas on natural selection by introducing them to the artificial selection programs breeders had long used.
5. Darwin’s ideas on natural selection put variation at the forefront of evolutionary change. In this way, they differed dramatically from the transformational evolutionary changes that Lamarck had suggested at the start of the nineteenth century.
6. Charles Darwin had two great insights: (a) natural selection occurs because populations are variable and because some individuals are more successful than others at surviving and reproducing in their environment, and (b) all species have descended from one or a few common ancestors; species that share a recent common ancestor tend to resemble one another in many respects for the very reason that they share recent common ancestry.