1) Evolutionary mammalogy is perhaps one of the most exciting fields in
the study of mammals- -at least to me.  Ideas once considered impossible
to prove are now, with advanced techniques and the constant accumulation
of fossils, are beginning to show the true relationships of mammals.  It
also shows something veterinarians knew all along; mammals are remarkably
similar in nearly ALL physiological functions.  Yes, differences exist
(duh!), such as the bears being able to recycle wastes so they can
hibernate and survive winter starvation, or llamas having convex, oval
red blood cells so they can contain more hemoglobin while still being
able to squeeze through capillaries and survive at high altitudes.  BUT,
these differences are DERIVED traits, not ancestral.
 
Ancestral traits are those shared by all members of various related
groups.  For example, an ancestral mammalian trait is five digits on the
hands and feet.  However, because of specific adaptations, horses only
have one and elk have four digits.  These changes in the number of digits
are considered to be derived characteristics.  Physiology follows similar
rules; all mammals have a very similar physiology, but specific
adaptations have caused some changes that are derived away from the
ancestral blueprint.
 
Remember the earlier discussion that compared formal analogies to
relational ones?  When ancestral characteristics are compared, they are
generally considered relational analogies, such as when comparing a human
stomach to a ferret stomach- -the two are so similar one is used as a
model for the other.  When derived characteristics are compared, they are
generally considered much weaker formal analogies, such as when comparing
a cow stomach to that of a ferret- -while both have a common (and
distant) ancestry, the cow=92s stomach is quite complex while the
ferret=92s stomach is fairly simple.  Mammalian physiology follows the
same rules.  Anything considered part of the ancestral pattern can
generally be considered a relational analogy, while derived characters
evolved afterwards are considered formal analogies.
 
The importance of derived versus ancestral characters is evident when
studying the effects if dietary restriction.  The observational data show
the benefits of DR cross mammalian species-lines; in ALL mammals tested,
the benefits are more or less the same.  Differences do exist, but NOT
in the type of expression, but rather in the degree.  For example, one
mammalian species may experience a doubling of life span, while another
might only see perhaps a quarter increase.  If effects of DR were a
derived trait, then it would only be found in a limited number of
closely-related species.  Because it has been seen universally in
distant, poorly related species, it can be considered an ancestral
trait, and in those species where the phenomenon is diminished or absent,
the lack can be considered derived.
 
None of this--by itself--actually proves ferrets would harvest the same
benefits from dietary restriction.  For that, we need studies specific to
ferrets (some are being done at this time).  Nonetheless, we KNOW dietary
restriction works with dogs and cats.  For example, a form of dietary
restriction is practiced in large breed dogs to prevent hip dysplasia,
and both cats and dogs remain healthier if placed on a lower calorie diet
in later life.  Experimental studies have linked the positive benefits of
DR in mink, beagles, Maine coon cats, and numerous wild carnivores housed
in zoological parks.  The trait is clearly an ancestral one in both
mammals and carnivores, and it is a safe assumption to accept the
characteristic is endemic to ferrets, until undeniable proof otherwise
is offered.
 
Bob C
[Posted in FML issue 3958]