If we try to describe the picture, I could say that judging from the left hand side, humans used to ride on the power of other humans (manual labor) , but as time progressed, it got to the era where humans starred to ride on the power of other beings (animals).

However, for this to illustrate the progress of human evolution, I think it has to somehow incorporate an illustration of the use of robots because we don't ride on donkeys again.

This is just my thoughts. I may be wrong though.