Don't look into our history for the answer. Look into Sumerian history of what the Annunaki gods told them.
Apparently there was a revolt among the miners (Igigi slaves and some lesser Annunaki) over the working conditions in the gold mines and they went to Enlil's house (Annunaki commander) and things got heated. Enlil was going to have them all killed, but his brother, Enki (#2 in charge) stepped in and agreed with the miners and a compromise was worked out where a primitive worker (humans) would be created to do the work by genetically upgrading local primates (homo erectus) to relieve the Igigi and rank and file Annunaki of the manual labor.
Enlil agreed on certain conditions, that their lifespans would be limited to 120 Earth years, their strength and intelligence would be limited, and other stuff I forget…I think they would be disease prone vs resistant, limited to hosting one spirit per body vs other combinations which apparently Annunaki could do…etc.
This was to prevent them from another mutiny like the one that was put down.
There's clearly so much more, but our whole history makes sense when you're exposed to the oldest histories…not the power and control narratives we're fed to keep us cattle in the pen.