One of the major dialogues in evolutionary genetics in the 20th century was that between R.A. Fisher and Sewall Wright. It is so seminal that the term Fisher-Wright controversy is often used. One of the major points of disagreemant between Fisher and Wright was the role of population substructure and the relevance of long term effective population size in shaping the trajectory of allele frequencies over time. At my other blog David B is starting a series which addresses this issue. The initial post deals with the period before the publication of The Genetical Theory of Natural Selection.