Darwin signaled the preeminent importance of natural selection in both the title and subtitle of his book the Origin of Species. But without variation as the raw material upon which selection can act and inheritance as the means for preserving favorable variations in the future, natural selection would not lead to the genesis of new species. How, then, did Darwin present these two topics in the Origin? Answering this question will require textual analysis of the first edition of the Origin, including some reference to changes in later editions, and a little indulgence in somemore speculative discussion of the subject. The chapter will address the following questions:

1. Why did Darwin privilege variation in 1859?

2. Why did he hold that changes in the conditions of life provide the chief raw material for evolution?

3. Had Darwin known of Mendel’s critique of his work, how might the sixth edition of the Origin have differed from what was published?

INTRODUCTION

To the contemporary reader with some knowledge of modern biology, the crucial importance of heritable variation to the theory of species transmutation has no need of justification. It is obvious. Yet Darwin’s manner of presenting it and the theoretical stance he adopted must seem strange, even extraordinary.