Explain the role of literacy in the overthrow of the Inca according to Guns, Germs, and Steel?

The answer to this can be found in Chapter 3.  It is on
pages 78 and 79 in the paperback edition.  The answer can be found in the part where
Diamond is telling us why the Spanish came to South America instead of having the Inca
come to Europe.

Diamond argues that literacy was a major
factor in why the Spanish were able to cross the ocean while the Inca were not.  Diamond
says that literacy allowed information to "be spread far more widely, more accurately,
and in more detail" than was possible for any society that did not have writing.  The
accounts of Columbus's voyages could be published, making people aware of the New World
and eager to go there.

At the same time, the Inca did not
have writing.  This helps explain why they walked into a trap that Pizarro set.  The
Inca who met the Spanish were not able to send accurate and detailed reports to the
government.  This made the government much less aware of what the Spanish were capable
of doing.

These were the major reasons why literacy was
important in causing the Spanish to be able to overthrow the
Inca.