According to the Epilogue of Guns, Germs, and Steel, what are the important factors in the development of civilization?This can be found in the...

Beginning on the second page of the Epilogue (page 406 in
the paperback edition), Diamond gives a list of four kinds of factors that determine
which continents will develop the most complex civilizations.  These factors are all
environmental or geographical.  They are:

• The
  number of species of plants and animals that can be domesticated in any given area.  The
  more species, the better for civilization.


• The chances
  for diffusion and migration within a continent.  If a continent has a long east-west
  axis, the chances of diffusion and migration are higher.  This makes the development of
  civilization more likely to occur.


• The ease of diffusion
  between continents.  The easier diffusion is, the more likely civilization is to
  arise.


• Total population size.  The more people there are,
  the more potential inventors of technologies that will lead to more
  civilization.

These are the factors cited by
Diamond in the Epilogue.