Syntactic change has occurred in English. Two examples of this are negation and do-insertion in questions.
Though the use of the double negative is now considered incorrect, it was once quite common in English. For example, Geoffrey Chaucer, often called the father of English literature, used many double negatives in his poetry. In "The Canterbury Tales", he describes the friar in this way: "Ther was no man no wher so vertuous". This means "There was no man nowhere so virtuous". Of course this sentence is now considered ungrammatical and can be changed to: "There wasn't a man anywhere so virtuous".
Another syntactic change occurred in questions. Today inversion occurs with modals and auxiliaries but not main verbs. "Can you swim?" and "Is he coming?" are examples of inversion but with main verbs we insert "do". This gives us questions such as "Do you like fish?" and "Do you dance?" In the past, however, these questions were formed with inversion, not do-insertion. They used to be "Like you fish?" and "Dance you?". This is the pattern in all Germanic languages other than English. For example, Norwegian has "Liker du fisk?" and "Danser du?" for the English questions. German has "Magst du Fisch?" and "Tanzt du?"
It may be that structures such as "Do you like fish?" developed from the insertion of "do" in sentences as an emphatic verb. "I do like fish" is stronger than "I like fish". If this was the case, it then inverted to form questions as is the case with English auxiliaries and modals. In any case, the use of "do" in questions with main verbs and the lack of double negation are syntactic changes which occurred in the English language.