Yes, I believe you have it right about the Sphinx, Donuel. It was almost certainly sculptured in its original form of a lion by a civilization far older than Egypt. Major climatic changes occurred causing decades or even centuries of heavy rainfall, eroding its sides and arms. In a later and far dryer period the Egyptians carved its lion head down some into the likeness of their Pharoah.

The civilization(s) which preceded Egypt are lost to known history, probably because of major climatic changes or other disastrous Earth changes which brought them to an end and reduced the people in those areas to bare survival levels for thousands of years. In time, though, complex civilizations rise again.