ancestor vs predecessor

ancestor

noun
  • One who had the same role or function in former times. 

  • One from whom an estate has descended;—the correlative of heir. 

  • One from whom a person is descended, whether on the father's or mother's side, at any distance of time; a progenitor; a forefather. 

  • An earlier type; a progenitor 

  • A word or phrase which serves as the origin of a term in another language. 

verb
  • To be an ancestor of. 

predecessor

noun
  • One who precedes; one who has preceded another in any state, position, office, etc.; one whom another follows or comes after, in any office or position. 

  • A model or type of machinery or device which precedes the current (or later) one. Usually used to describe an earlier, outdated model. 

  • A vertex having a directed path to another vertex 

How often have the words ancestor and predecessor occurred in a corpus of books? (source: Google Ngram Viewer )