https://buske.de/the-impact-of-a-sovereign-default-within-the-euro-zone-on-the-exchange-rate.html/
All five evolutionary paths picked out in grammaticalization theory, that lead to reciprocal markers in human languages, are shown to have been active, albeit at varying degrees, in medieval Spanish and Portuguese texts, as well. Compared to their Latin forerunner, these two Romance varieties were most innovative on two points. First, all kinds of Latin reiterated reciprocal clusters, after having been subsumed under one common structure (alter alterum), were subsequently reanalyzed as bipartite correlated markers (