This is second part in my series on natural selection.  In the first part, I discussed different modes of selection; in this post, I’ll explain an important mechanism of natural selection which probably doesn’t get enough attention in basic biology courses.  The idea, called sexual selection, dates back to Darwin, who dedicated over half of one of his books (The Descent of Man and Selection in Relation to Sex) to the subject.  Sexual selection is based on the struggle to reproduce rather than the struggle to survive; this already gives us a hint that the term “fitness” has a different meaning in evolutionary biology than it does in common speech, which is a subject I’ll get to in a later part of this series.

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