protohistory

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The study of a culture just before the time of its earliest recorded history.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The period between prehistory and history, during which a culture or civilization has not yet developed writing, but other cultures have already noted its existence in their own writings.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the study humans prior to the invention of writing