The origin of human language has sometimes been called possibly “the hardest problem of science.” (Christiansen and Kirby, 2003).
We assume, following Chomsky that the key properties of human language syntax can be accounted for by a single, combinatorial operator called “Merge”. We characterize Merge and ask how can we connect the abstract operation of Merge to biology? We assume a similarity between Merge and metrical structure then obtaining an entrée into animal models for human language. To test this hypothesis, we propose to determine whether the Halle rule system also fixes the space of possible vocal patterns in songbirds.