One approximation suggests that a barrel of oil contains roughly 4.5 to 6 years of human labor,
That tells us nothing. I have to chew on this.
One gallon of diesel can take a fully loaded semi up a 10% grade over a mountain pass and the engine will cut out just as the truck reaches the summit.
Now using a series of posts sunk into the road on which hand winches can attach we find out how long it takes One Joe Six Pack to winch the truck up the same path.
Several weeks of cranking to produce the same result for sure. The time to move between hitching posts does not count. Diesel is obtained from a barrel of crude at an efficiency of slightly less than half. So twenty gallons (a barrel is 42) times several weeks.
Is in the ball park of 4.5 to 6 years considering a barrel gives more than diesel when it is refined.
* If the earth is 4.5 billion years old and Sisyphus had been rolling stone all that time he would have rolled up the equivalent of a third of Alaska's total oil endowment (as of 2021) in terms of energy used. But Sisyphus is a good stone roller. He would have put out the equivalent of all of Alaska's oil by now.
Twenty thousand slaves harnessed in front of a semi truck like the twenty mule teams of the old west could haul the semi no problem. Only a few hundred would be needed.