  Languages disfavor word forms containing sequences of similar or identical
consonants, due to the biomechanical and cognitive difficulties posed by
patterns of this sort. However, the specific evolutionary processes responsible
for this phenomenon are not fully understood. Words containing sequences of
identical consonants may be more likely to arise than those without; processes
of word form mutation may be more likely to remove than create sequences of
identical consonants in word forms; finally, words containing identical
consonants may die out more frequently than those without. Phylogenetic
analyses of the evolution of homologous word forms indicate that words with
identical consonants arise less frequently than those without, and processes
which mutate word forms are more likely to remove sequences of identical
consonants than introduce them. However, words with identical consonants do not
die out more frequently than those without. Further analyses reveal that forms
with identical consonants are replaced in basic meaning functions more
frequently than words without. Taken together, results suggest that the under
representation of sequences of identical consonants is overwhelmingly a
byproduct of constraints on word form coinage, though processes related to word
usage also serve to ensure that such patterns are infrequent in more salient
vocabulary items. These findings clarify previously unknown aspects of
processes of lexical evolution and competition that take place during language
change, optimizing communicative systems.
