There is a good 1000-2000 years (roughly) between the Egyptian pyramids and the Mesoamerican ones. Also consider the different uses to which they were put -- tombs vs. temples.

No aliens necessary, just lots of people. What would you say to the claim that the biggest Indian temples were built by aliens and not humans?

Fred

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"For shame, gentlemen, pack your evidence a little better against another time."
-- John Dryden, "The Vindication of The Duke of Guise" 1684