Cairo ? Egypt displayed on Monday newly discovered tombs more than 4,000 years old and said they belonged to people who worked on the Great Pyramids of Giza, presenting the discovery as more evidence that slaves did not build the ancient monuments.

The series of modest nine-foot-deep shafts held a dozen skeletons of pyramid builders, perfectly preserved by dry desert sand along with jars that once contained beer and bread meant for the workers’ afterlife.

The mud-brick tombs were uncovered last week in the backyard of the Giza pyramids, stretching beyond a burial site first discovered in the 1990s and dating to the 4th Dynasty (2575 B.C. to 2467 B.C.).

The ancient Greek historian Herodotus once described the pyramid builders as slaves, creating what Egyptologists say is a myth later propagated by Hollywood films.