> Egyptologist Mark Lehner, an associate of Harvard's Semitic Museum, is beginning to fashion an answer. He has found the city of the pyramid builders. They were not slaves.

Idk man, seems like the article does claim that the builders weren't slaves.

Also, given the way trophic pyramids work, feeding crops to a cow and feeding the cow to people results in a loss of energy compared to feeding the people plants. By that, I mean it's more expensive to raise a cow and use it to feed 10 people than it would be to give those 10 people crops.