Toynbee's Six Civilizations Without Precedents

On p. 48 and elsewhere in Somervell's abridgment of The Study of History, Toynbee states that of the 21 civilizations that are identifiable, in all of time (I love his willingness to say what he sees rather than to say, "Uh, I don't know.  The record is incomplete.")  six civilizations had no known antecedents.

He's going to go into the history of the Egyptiac, Sumeric, Minoan, Sinic (Yellow River in China), Mayan and Andean as civilizations that sprang up from nothing.  And only the Egyptian had no descendants.  Is this why I love Egypt?


A word about adjectives.  Why can't we just say either Egyptiac or Egyptian?  Is there a difference?

I hate when people say Mosaic meaning pertaining to Moses.  Mosaics are already something else, so let's not drag art into the study of Bible, history or civilization- thank you very much.