This appendix discusses two historical issues, relevant to the development of Jamaican Creole (JC). First, it discusses a functional relationship between long mid vowels and diphthongs, which may constitute a push chain shift. Second, the alleged historical phonological process of unmerger, which would seem to be necessary part of a certain outdated view of creole history, is defined and shown not to exist. Two classes of counterexamples (doublet borrowings in Arabic, and near-mergers) are argued to be false counterexamples. The empirical principle that mergers are irreversible is thereby validated. Finally, the consequences of this principle for theories of the historical development of creoles in general, and Jamaican Creole in particular, are outlined.