The thresher separated grain from straw and chaff. At threshing time, several neighbors and many itinerant workers assembled at our farm. With luck, no rain fell and the grain was safely stored in the granary within a few days. Now, a combine rolls into a field. In a matter of hours, one or two workers harvest and store the grain.
Labor is reduced at least tenfold.
Similarly, for harvesting alfalfa. What took many days and people is now accomplished in a few days with one or two people. I left the farm, completed military service, then enrolled at the University of California at Davis in the Agricultural Engineering Department. Its researchers were world-renowned for developing machines for field production. Field production machines are important because each replaces ten or more workers.