One of the wearisome problems of using the body of scientific literature
to delve into specific ferret problems is the limited nature of that
literature.  While ferret information is rich in those areas used to
model human and canine disease, it is frustratingly sparse in those areas
that mean the most to ferret owners (this is gradually changing).  While
you can use the literature to discover a tremendous amount of information
regarding influenza in ferrets (done to model the disease in humans), or
on distemper (done to model the disease in dogs), finding pertinent
information about nutrition is rather restricted.
 
As mentioned, ferrets have been used to model disease in humans and
canines.  When an animal is used in this regard, it is a specific type
of modeling called either an analog or a homolog.  In the simplest
biological definition, a homolog is similar structures with a common
ancestry, like a human hand and arm, the front flipper of a whale, a bat
wing, and a ferret front leg.  An analog is similar structures without a
common ancestry, such as the wings from a butterfly and hummingbird.
These definitions are simplistic in terms of modeling disease because
although ferrets and humans are mammals with a homologous physiology,
they are not exactly the same.  Mustelids diverged from the common
mammalian lineage nearly 18 million years ago, and differences between
the two have been slowly introduced since that time.  It is clear that
two structures or physiologies may, in fact, be biologically homologous,
but enough differences may exist to shift them back to analogs.  For
example, dogs and humans share homologous physiologies, but dogs cannot
eat Tylenol or chocolate.  So, while the physiology between the two
species are homologs in a general biological sense, in a specific
physiological sense they are more like analogs.
 
The problem was addressed by Hodder, who in 1982 distinguished FORMAL
from RELATIONAL analogies, arguing formal analogs were far weaker models.
Simplistically, the simplest way to distinguish between the analogies is
that in a formal analogy the similarities are inferred, while in a
relational analogy the similarities are observed (the difference is far
more complex, but beyond the scope of this discussion).  A dog's
inability to eat Tylenol or chocolate while a human can, demonstrates the
two are formal analogs and are not relational.  This is why the human
ability to metabolize chocolate cannot be used to directly model canine
theobromine metabolism.  When ferrets are used to model canine distemper
in dogs, the observable similarities support the use of a relational
analog.  This means the data generated from ferret distemper studies can
be used to generate hypotheses regarding the disease in canines, as well
as using the disease in dogs to model distemper in ferrets.  In a
relational analogy, data can be used in both directions.  It also means
that if a ferret is a relational analog for a disease in dogs, and dogs
are a relational analog a disease in, say, raccoons, then raccoons and
ferrets can be used to model the disease in the other.  Scientists are
skeptical, conservative bastards, so a confirming experiment is desired,
but not necessary for the creation of hypotheses.
 
This is critically important because it directly affects the use of
other species to fill in gaps in our knowledge of ferrets, as well as
how we use and interpret hypotheses.  There is a lot of misunderstanding
regarding what a hypothesis is, and how it works.  A hypothesis is
nothing more than an idea or proposition that is based on certain defined
assumptions that can be evaluated scientifically.  What that means is the
hypothesis itself IS NOT tested, but the assumptions it is based upon are
confirmed or falsified.  If the assumptions are falsified, that is,
proven wrong, then the hypothesis is rejected.
 
Bob C
[Posted in FML issue 3949]