  Statistical properties of the taxonomic classification of human languages are
studied. It is shown that, at the highest levels of the taxonomic hierarchy,
the frequency of taxon members as a function of the number of languages
belonging to each member decays as a power law. This feature reveals that a
self-similar structure underlies the taxonomy of languages, exactly as observed
in the taxonomic classification of biological species. Such an analogy is a
clue to the evolutionary foundation of language classification based on
long-range comparison.
