In the past thirty-five years, second language acquisition theory has evolved from the structural/descriptive school of thought, through contrastive analysis, error analysis, and the hypothesis that second language acquisition is no different from first language acquisition, to the currently popular interlanguage hypothesis. Simultaneously, linguists have been examining the universal nature of language. Beginning with Trubetzkoy and Jakobson of the Prague School and continuing with Greenberg, Chomsky, Stampe, and others, linguists have been searching for structures and processes common to all languages, and for answers concerning the innateness of human speech. Until answers to such questions are found, "questions relating specifically to the learning of [a second language] can be answered only tentatively". Meanwhile, it is beneficial to periodically assess the gains that have been made in the various fields of language research to see if any of the pieces of the puzzle of human language acquisition are beginning to fit together.