Where in Guns, Germs, and Steel do you find the difference between proximate and ultimate factors?I know what they are, but I need to know where...

There are a number of places in this book where you can
find Diamond discussing the difference between proximate and ultimate
factors.

The first place where Diamond gives a useful
definition (or a hint at one) is in the Prologue.  On page 23 in the paperback edition,
Diamond tells us that proximate causes are those that identify "immediate causes." 
Still in the Prologue, on page 28, Diamond tells us that ultimate causes are the ones
that lead to the proximate causes.

The best place to see a
graphic illustration of the difference between these types of factors is in Figure 4.1,
on page 87.  There, Diamond gives us a flow chart that shows how ultimate factors led to
the proximate factors that made European countries stronger than those of the Americas
and other such places.

While there are many other mentions
of proximate and ultimate causes, these three should serve to illustrate the meaning of
these concepts.