What does this say about history in general and historical evidence in particular?Colin Thubron said, "Marco Polo produced a travel portrait so...

This quote tells us a few things about history and the
nature of historical evidence.

First, it tells us that it
is not always easy to know which historical witnesses are telling the truth.  It is
clear that not every account written of a journey to some far off land (or account of
things that happened in some past time) is true.  Occasionally, however, they are.  It
is hard to know which is which unless you are able to actually go to the place involved
and examine the evidence.

Second, it tells us that
historians are prone to interpreting evidence through the lenses of their own prejudices
and beliefs.  Marco Polo's account seemed outlandish compared to what historians once
believed to be true.  Because the evidence was contrary to their view of what was likely
to be true, they discounted the evidence.

This quote shows
some of the difficulties of studying history -- we often have to rely on accounts that
may or may not be completely truthful.  In deciding what is true, we are handicapped by
our own preconceived notions about what should be true.