In "Verbs and Tenses" by George Davidson, the author discusses how to form questions in English. One of the rules presented was if the declarative statement doesn't contain an auxiliary to front, "do" is used. For example: He likes Susan / Does he like Susan?
I noticed that in all of the declarative sentence examples one could switch in "do" or "did" to indicate the tense of the sentence. For example, "He cooked dinner," could be expressed "He did cook dinner." "He likes Susan." could also be expressed "He does like Susan."
I can't remember all of the examples but I remember seeing this construction a lot in "older" English. I put older in quotes because I don't know the exact time and I understand this is important when talking about the historical development of English. I think Shakespeare uses this construction. Perhaps "He doth protest too much."
I also noticed that the "s" in "does" gets shifted to the verb and that the "d" in "did" gets shifted. "He does go to London." becomes "He goes to London." The "do" is dropped and the "es" gets shifted to "go" In "He did ask a question." The "di" is dropped and the "d" is shifted to "ask." In modern English, we use "ed", but I think "askd" was acceptable at one time. (perhaps I am mistaken on this.)
My question: Was "do" a present and past tense marker in earlier forms of English?