For a while I've been researching this question and its quite obvious there's no ONE ANSWER-just a series of different conjecture and educated guesses. Any ideas? Especially Giza,whose erosion shows it as erected at least 9,000 bc when Egypt was still wet. It would seem the other pyramids built afterward in S.America and China, were built in the same technique since they were erected after all by African migrants. Am open to logical conjecture and informed speculation.