"The approach that McCarthy has taken is the stuff of which Kuhnian revolutions are built. He has taken many puzzling and sometimes troubling aspects of conventional neo-Darwinian evolutionary thought, and woven them together to motivate a grand novel hypothesis (stabilization theory) that interprets these problematic areas in a new light. Among the contentious subjects that McCarthy reinterprets and purports to resolve in the light of stabilization theory are the following: the concepts and definitions of species and why these have so long remained controversial; the origin and role of karyotypic changes in the evolutionary process (a topic that has been largely neglected since the 1950s); the puzzlement of why different gene trees seem so often seem to support different organismal phylogenies; general uncertainties about the mechanisms and processes underlying reproductive isolation; and the issue of how to reconcile the appearance of punctuated stasis in the fossil record with the well-known mechanisms of traditional population genetics. McCarthy argues that these and other major dilemmas under traditional speciation theory largely dissolve under the evolutionary scenario he develops, wherein hybridization often provides the initial stimulus and fodder for evolutionary change by introducing into lineages a wealth of otherwise unavailable genetic variation (especially karyotypic) from which new species then sometimes emerge as stabilized recombinant derivatives. The hypothesis is bold, at least plausible, difficult to broadly refute, and yet also ultimately testable. Such testing can involve, for example, more critical appraisals of whether (and if so, why) gene trees often lack full concordance with one another in the organismal trees they seem to support. [Is this because of homoplasy and the idiosyncrasies of lineage sorting (as is often supposed in much of the recent literature), or is it because evolution is far more reticulate than formerly imagined] Many other research lines are also suggested, directed for example toward understanding both descriptively and experimentally the actual consequences of interspecific hybridization. Indeed, this book should stimulate fresh evolutionary perspectives, worthy of further exploration, in a wide set of research arenas."