According to the Integration Hypothesis, human language is the combination of the Expressive (E) component and the Lexical (L) component. At the level of words, the L component contains the concept and meaning that we want to convey. The E component contains grammatical information and inflection. For phrases, we often see an alternation between the two components. In sentences, the E component is responsible for providing the shape and structure to the base-level lexical words, while these lexical items and their corresponding meanings found in the lexicon make up the L component. This has consequences for our understanding of: (i) the origins of the E and L components found in bird and monkey communication systems; (ii) the rapid emergence of human language as related to words; (iii) evidence of hierarchical structure within compound words; (iv) the role of phrases in the detection of the structure building operation Merge; and (v) the application of E and L components to sentences. In this way, we see that the Integration Hypothesis can be applied to all levels of language: the word, phrasal, and sentence level.