Which or Who, Which should I use? [closed]
Yes, the rule says use who when referring to people. In this case though the humans are not being treated as people, but merely as factors. I could write Advanced tool-using hominids are the only factors which ..., and I think most people would agree with which even though all advanced tool-using hominids are humans.
Therefore I would prefer which to who. Using that is a neat way of avoiding the question because it may be used for both human and non-human situations