I have been fortunate to do extensive travel andmy favorite of all the stops has been the Sphinx. Workers carved the man-lion hybrid, whose face likely depicts the Pharaoh Khafra, into a limestone bedrock hill. It remains one of the world’s most recognized sculptures thousands of years after its construction. But how many thousands of years is that?
Whether built by Egyptians or aliens, these workers left behind plenty of evidence of their time spent there. Radiocarbon dating evidence shows the tools, housing, and ovens employed by Sphinx workers were in use around 2500 BCE. Despite a strong consensus among archaeologists, geologists, and Egyptologists about this date, a few non-experts prefer a contrary timeline.
There was, for example, a 1990s television movie, The Mystery of the Sphinx: New Scientific Evidence, which suggests it was built much earlier. Also, science fiction author John Anthony West and alchemist René Adolphe Schwaller de Lubicz have both claimed the extent of wall erosion surrounding the Sphinx is much greater than other places in Giza. The duo claim this could only happen if the limestone lion had been exposed to the elements thousands of years before the consensus date of 2500 BCE.
But Skeptoid’s Brian Dunning points out that weathering can result from desert winds combining with native sand. Also factoring in is how soft the limestone would have been when the Sphinx was being built. Contrarians believe the weathering is best explained by water that flowed near the Sphinx site during a period when there was much greater rainfall. However, archaeologists have excellent paleoclimatology data for the region, so they know rainfall there 4500 years ago was much heavier than what it is today.
Crucially, the Giza Plateau is high ground and the area encompassing the Sphinx and Pyramids is a summit and is therefore a highly unlikely place for water to flow to. Furthermore, almost all geologists maintain there is little reason to try and squeeze water erosion into this Egyptian equation. Dunning writes, “The pattern of erosion on rock depends not upon what’s doing the eroding, but upon the characteristics and hardness of the rock itself. It’s impossible to tell what did the weathering, water or wind.”
And according to geologist August Matthusen, “Variations in the rock usually account for the different weathering morphologies.”
There are a number of ways to explain why there is significant weathering found on the Sphinx’s deep west wall and no other place on the plateau. These reasons include salt crystal exfoliation, underground water, and excavation.
To make the alternate hypothesis work, contrarians propose the existence of an earlier advanced civilization that preceded Egypt. The deficiencies with this idea are the geological evidence presented so far and the lack of proof of a society large and advanced to build the Sphinx, then disappear – all without leaving traces of themselves.
In the Encyclopedia of Dubious Archaeology, Dr. Ken Feder writes, “There is no sign of an infrastructure necessary to support a large population of workers, no sign of the ability to produce a large agricultural surplus to feed the construction workers, no evidence of dormitories for housing them, no huge storage facilities for food, no great bakeries, no cemeteries in which to bury the workers who would have died during the construction project.”
And one doesn’t need an alternate history anyway. The Sphinx is magnificent enough on its own. My amazement when gazing upon this ancient wonder would not have been any more pronounced by thinking it was even older or by suspecting that sleuth pseudoscientists had exposed a cover-up.
molineskeptics.com 
How accurate is the radiocarbon system? What is the error rate? How do they know? What system do they use to check for accuracy? Do they use a control measure?
***I’m (obviously) asking for a friend***