Abstract

The importance of _naturalization_—the establishment of species introduced into foreign places—to the early development of Darwin’s theory of evolution deserves historical attention. Introduced and invasive European species presented Darwin with interpretive challenges during his service as naturalist on the HMS _Beagle_. Species naturalization and invasive species strained the geologist Charles Lyell’s creationist view of the organic world, a view which Darwin adopted during the voyage of the _Beagle_ but came to question afterward. I suggest that these phenomena primed Darwin to question the “stability of species.” I then examine the role of introduced and invasive species in Darwin’s early theorizing and negotiation with Lyell’s ideas, recorded in his post-voyage “transmutation notebooks.” Therein, the subject was an inflection point in his contention with Lyell’s views and moreover, his theorizing on invasive species occasioned some of his earliest inklings of natural selection. Finally, I examine how naturalization was crucial to Lyell’s own eventual conversion to evolutionism. I conclude with brief reflections on the implications of this narrative for our understanding of Darwin’s reasoning, his intellectual relationship to Lyell, and the historical context that shaped his theory.