In Guns, Germs and Steel, why did Eurasia have the most domesticated animals of all continents?

There are two
basic reasons for this fact.  First, Eurasia had a greater number of large wild mammal species
than any other continent did.  Second, fewer large animal species were made extinct in Eurasia
than elsewhere.  Finally, Eurasia was just lucky to have "good" animals.

In my copy of the book (paperback edition) the first of these facts can be found on p.
162.  The second is on p. 163.  The third idea is the main point of the whole chapter, but is
also on p. 174, which is the next to last page of the chapter.

What Diamond
is arguing is that it is much more likely that an animal species will be poorly suited for
domestication than that it will be well suited.  (There are more ways for a "marriage"
to be unhappy than happy.)  Eurasia happened to be lucky enough to have a lot of species, many
of which were suited for domestication.