Q: "You...mentioned that ferrets have not been subjected to the 'dumbing
down rule of domestication.'  I'm not sure I agree with that.... Some of
this may well be attributable to the lack of stimulation and variable
environments at an early age...but all of it??"
 
A: Ferrets may not have been subjected to the dumbing down rule, but I
think I have been... ;-)
 
A domesticated animal is one that is in human control, selectively bred
by humans, maintained (housed, fed) for human use, and has had at least
one characteristic (color, size, behavior, etc.) changed to meet human
desire.  This is a modern and well-accepted definition, but it isn't too
far from Darwin's original definition (1859, 1868) which included being
oriented towards achieving some human-goal, captive breeding,
morphological changes (defined as increased fecundity, atrophy of certain
organs, smaller size, more variation), can happen without conscious human
effort, and the ever-important "tameness towards humans" (a common
Victorian requirement).  It was this last requirement that continues to
cause some sticky problems regarding ferret domestication.  Essentially,
Darwin anthrocentrically argued the more domesticated a species, the
tamer it was towards humans (the dog being the archetypical example).
Yet, animals that were not as tame towards people as others were still
clearly in a state of domestication, so the conundrum was answered by
using the term "semi-domesticated."  Thus Victorian scientists ignored
the reactions of feral and abandoned dogs and cats towards people, but
seized on the reactions of poorly handled, badly socialized ferrets,
labeling them "semi-domesticated."  Thankfully, excepting those Wizards
of Obtuseness, the CaCaLand Fishing Gestapo and Cranioanal Impaction
League, the idea of an animal being "semi-domesticated" has been largely
abandoned in favor of a more enlightened theory of domestication.
 
One of the observations made during this early demarcation of
domestication was that changes took place in the size and shape of the
skull.  Generally, the facial bones of the skull are shortened, giving
the animal a more juvenile, pug-like face.  Another observation was that
the cranial volume, the measure of the space that houses the brain, was
smaller in domesticated animals.  Some animal behaviorists, seizing on
the differences in behavior observed between domesticated animals and
their wild progenitors, suggested domesticated animals were not as
intelligent, the infamous "dumbing-down rule of domestication".  Later
investigations suggested the brain of domesticated animals was smaller,
but the difference in size reflected smaller sensory regions of the
brain, and not necessarily regions impacting intelligence.  Nonetheless,
people working with both wild and domesticated animals could intuitively
tell that wild animals were somehow smarter than their domesticated
counterparts, so the "dumbing-down" rule became part of the common
knowledge of domestication.
 
Research done during the last few decades has called this common
knowledge into question.  It has been discovered that developing brains
are extremely plastic in their responses to environmental influences
(that is, capable of adapting to different conditions during early
development).  For example, ferret kits that are exposed to lots of
different odors will have more nerve connections to the areas of the
brain sensing smell; they can detect more odors and the brain can
interpret them better (the basis of olfactory imprinting).  The effects
of the visual environment on the growth of specific eye structures is
astounding; just the prevalence of predominately vertical lines over
horizontal ones can change the development of several structures within
the eye, optic nerve and brain (meaning cage environments can literally
result in different vision compared to those raised outside cages).  The
early separation of babies from their mothers has been shown- -across
species- -to result in profound changes in the brain, which one recent
paper has demonstrated to be minimized by an aggressive enrichment
program during juvenile development.  Environment has such a profound
influence on brain development that it can even influence mental concepts
of gender, as shown in studies of identical twins (genetic clones) where
one has gender-specific sexual orientation, and the other feels trapped
in the wrong body.
 
Bob C
[Posted in FML issue 4314]