Nearly Forty years ago, a fellow engineer told me a story that must now be 70 years old. This engineer was born and educated in Egypt. His first job was a large civil engineering project with massive amounts of earth moving. Having a formal education but no local real world experience, he started to estimate how many steam shovels and trucks were required for the job. A Sr. engineer asked, what he planned do with all the equipment once the project was done, and what about the 99 local laborers left idle for each machine that does the work of 100 men and requiring only one operator?
The Sr. engineer told the young engineer to base his calculations on the required number of donkeys, basket weavers, strong men, little boys, and laborers that would be required. I was puzzled as was my colleague that many years ago.
The Sr. engineer explained that picks and shovels would be the main tools and the local laborers the muscle. The laborers loosen the soil and then fill the woven baskets with the soil. The strong men would lift the baskets onto the donkeys. The young boys would ride the animal off site and dump the soil. This kept the local population employed and able to feed their families. Manual labor as it was may not have been a great way to make a living but it was far better than starvation.
The situation in ancient Rome was similar. The Romans build magnificent structures but the preferred method was brute force. There was no push for efficiency as we think of it today. Even then, there were labor issues. Better to keep everyone working and fed, if only at subsistence levels, than to have massive unemployment and the making of a revolt.
If the laborers were in a position to demand higher and higher wages mechanization may have advanced faster. It will be interesting to see how many jobs robots and computers will replace as the minimum wage increases to $15/hour regardless of the local economies.