Evolutionary theory has stimulated debate ever since Darwin presented his ideas in 1859. Some disputes have been driven by the antievolutionary zeal of religious fundamentalists, whose dismay with Darwinian thought continues to this day-as witness the intelligent design movement (Forrest & Gross, 2003; Jones, 2005). But attempts to understand evolutionary theory have generated plenty of genuine scientific questions and controversies (Dawkins & Coyne, 2005). This chapter will review several of these issues as a way to organize some of the major ideas underpinning modern evolutionary psychology (see also Hagen, 2005).