Anyone ever see a bow drill, used to start fires, in operation? Ancient people were just as intelligent as we are. They would have done something very similar, except using something that would have cut holes at the end. It isn’t hard to understand that at all.
No the idea of a bow drill was thought of and discarded by the archeologists - for the why, you’ll have to read their reports; I have no references to give you where they are located on the web or in some journal.