procreation vs proliferation

procreation

noun
  • The process by which an organism produces others of its biological kind 

  • The sexual activity of conceiving and bearing biological offspring 

proliferation

noun
  • The process by which an organism produces others of its kind; breeding, propagation, procreation, reproduction. 

  • The act of increasing or rising; augmentation, amplification, enlargement, escalation, aggrandizement. 

  • The result of building up; buildup, accretion. 

  • The spread of biochemical, nuclear and other weapons of mass destruction to countries not originally involved in developing them. 

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