  Color naming in natural languages is not arbitrary: it reflects efficient
partitions of perceptual color space modulated by the relative needs to
communicate about different colors. These psychophysical and communicative
constraints help explain why languages around the world have remarkably
similar, but not identical, mappings of colors to color terms. Languages
converge on a small set of efficient representations. But languages also
evolve, and the number of terms in a color vocabulary may change over time.
Here we show that history, i.e. the existence of an antecedent color
vocabulary, acts as a non-adaptive constraint that biases the choice of
efficient solution as a language transitions from a vocabulary of size n to n+1
terms. Moreover, as vocabularies evolve to include more terms they explore a
smaller fraction of all possible efficient vocabularies compared to
equally-sized vocabularies constructed de novo. This path dependence on the
cultural evolution of color naming presents an opportunity. Historical
constraints can be used to reconstruct ancestral color vocabularies, allowing
us to answer long-standing questions about the evolutionary sequences of color
words, and enabling us to draw inferences from phylogenetic patterns of
language change.
