A Boston-based archaeologist has developed a theory that the Egyptians delivered stone to the pyramids at Giza through a system of canals and harbors, shedding more light on the mystery of how ancient people — sorry, not aliens — built the massive structures.

Mark Lehner, director of Ancient Egypt Research Associates, says his research indicates that, when the Nile River was in flood, Egyptians could steer boats laden with stone to a major port city at the pyramid complex.

The Egyptians, consummate engineers, cut waterways from the Nile through floodplain that now is covered by sand and the urban sprawl of Cairo, Lehner believes. Illustrations developed by Lehner show water within several hundred yards of the Great Pyramid, a startling vision to anyone who has long thought of them as being surrounded by dusty desert.

"The Egyptians were basically using the Nile as a huge hydraulic lift," he said in a telephone interview.

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