Hello, I am not a teacher,
but I believe I understand the meaning of your sentence. I think you are reading a newspaper or perhaps a book about mankind.
The autor is talking about the evolution of people in this world, the 'sixth mass' refers on the disappearance of the races (animals or the evolution of the man).
The writer think that the people on this Earth are killing themselves by they behaviour.
Have a nice day.
Student or Learner