Domestication of otherwise wild animals go way back. Cats have been our best weapons against rodents for 10,000 years. We had been breeding sheep and goats for their milk and mutton for almost as long. The date of dog domestication is...debatable, to say the least.
And then there are animals we thought we domesticated but, in reality, not completely. Among them is the elephant. In truth, we never really domesticated them, but instead captured them from the wild.
There are three extant species of elephant--the Asian, the African Forest and the largest of all the terrestrial mammals, the African Bush. Because people from places like India and Thailand put major emphasis of elephant imagery in their cultures, only the Asiatic had been habituated to serve humans. (Habituated, not full-on domesticated--there are differences.)
But let's say that we had spent thousands of years domesticating all three species of elephants, including the Africans. Would their meat and milk be good to eat, or would we breed them only for their size and their ivory? And would an army of domesticated African Elephants help the Egyptian laborers speed up the construction of megastructures, like the Pyramids?