Organ comes in an does this progression once, then guitar comes in, just strum 8th 
notes the whole time:

C Em Am G

C                     Em            Am         G
  It's been a million years since I last saw a caveman.
C                   Em     Am                 G    
  I like the way he walks, I like the fire he builds.
C                        Em                   Am                G
  We hunt the beasts and make the bird calls, we go to sleep at night.
C                   Em               Am     G
  We go to sleep at night, under the starry sky.


C Em Am G (x2)

C                       Em            Am         G
  It's been two million years since I last saw a caveman.
C                   Em     Am                 G    
  I like the way he walks, I like the fire he builds.
C                        Em                   Am                G
  We hunt the beasts and make the bird calls, we go to sleep at night.
C                   Em               Am     G
  We go to sleep at night, under the starry sky.

C Em Am G (x6)

C