"by who?" Not to put too fine a point on it, but it is better expressed "by whom?" the object of a preposition. This is the same conversation, only expressed in proper grammatical terms. We see here a similar theme. Since most people's sense of history begins at about the time of birth, history must be studied in order to be learned.
I will grant you that many things photographic have been done by someone already, but this does not mean there is no substance in doing it in one's own way. There will never be another Weston, Ray or Zoe but we still take pictures. Besides, there's always digital. tim