Alignment typology is the study of variation in the expression of argument structure across the languages of the world. The grammatical elements that combine to express alignment are argument flagging (case-marking), argument indexation (often on the verb or auxiliary, sometimes as second or other position clitics), constituent order, or the more covert properties control of coreference or parallelism with other constructions. Of these alignments, nominative-accusative is vastly more frequent, followed by the ergative-absolutive, semantic, and hierarchical alignment types. In a given construction, different individual grammatical elements often present different alignment patterns, e.g. ergative flagging but nominative verbal indexation and nominative control of coreference. This talk explores the sources of different alignment patterns and how different mechanisms of historical change have a differential effect in creating those alignment patterns : reanalysis creates an innovative construction with a consistent alignment across grammatical elements, whereas analogical change within a construction changes one grammatical element at a time, and so creates inconsistencies in alignment within individual constructions. These mechanisms are both implicated in studies of grammaticalization, but whereas reanalyses appear to have consistent directions of change, analogical changes do not.