Before revision:  The mechanism of the historical economic growth and of the growth of human population is yet to be explained but it would be a waste of time, money and human resources to try to explain the non-existing , self-created mysteries  described in the  Unified Growth Theory  .
After revision:  The mechanism of the historical economic growth and of the growth of human population is yet to be explained but it would be unproductive to try to explain the non-existing , self-created mysteries described in the Unified Growth Theory .