I stated in the last post that domestication is a form of evolution what is
under human selection.  To understand what I mean, you have to have an
understanding of selection.  Selection can be caused from a number of
factors, including sexual, climatic, predatory, behavioral, cultural, or
human (domestication).  Selection is nothing more than the process of
removing genes from the genepool (or leaving them in), for any reason.  For
example, if an albino ferret is eaten by a predator before reproducing or
sterilized by a pet owner, the end result is the same; those genes have been
removed from the genepool, that is, selected against.  Natural selection
only means that the forces that place selectionist pressures on an animal
are non-domesticationist in nature.  In other words, they are caused by the
weather, or predators, or failure to attract a mate, or any of thousands of
possible factors.  Darwin thought it was important to separate those factors
from those of human selection.
 
So it is clear that either natural or human factors will select for or
against an individual ferret.  To be selected against doesn't necessarily
mean the ferret has to die; it only means the ferret failed to pass it's
genes to the next generation.  Each and every neutered ferret has been
selected against, providing it was neutered prior to reproductive age, yet
they can live long and meaningful lives.  This is the point where the old
phrase "survival of the fittest" fails.  Now that there is an understanding
of population genetics, that old saying is never used anymore except by
theological zealots or the uninformed.  The reason is because it is untrue;
selectionist pressures don't eliminate everyone *but* the fittest; they
eliminate only the unfit.  The phrase should be "survival of the mediocre
and better," or, "the just good enough." That is because selection only
works against the marginal individuals.
 
"But what about the old and sick?" you say.  Remember selection doesn't
mean you have to die, only that you don't successfully reproduce.  If you
are able to get your genes into the next generation, then, even if you get
sick or are eaten, you haven't been selected against (of course, the longer
you live, the more of your genes get into the population, so there is an
advantage to survival past the first breeding year).  See where this is
going and why it is so important for an understanding of domestication?
Individuals do not evolve, populations do.  And the driving force behind
evolution is selection, because selection is the only force that can change
the frequency of genes in the population (mutation introduces new genes,
but it is selection that increases or decreases the frequency of the new
gene).  It is the shift in gene frequency that causes evolution.
 
Imagine a gallon pickle jar filled to the brim with marbles, randomly
colored so that you have a continuous spectrum.  Imagine there are equal
numbers of each color.  You don't like orange, so you pick out as many as
you can find, but you have to do it fast because when the buzzer goes off,
someone is going to refill the jar based on what is left (for every two red,
they will put in another red, etc.)  Now, its easy to see that removing the
orange marbles doesn't change the blue or green marbles, and its also easy
to see that you might sometimes accidently pull out a marble that is more
red or yellow than orange.  If you do this long enough, the jar will start
to look blue-green as the orange and marginal reds and yellows are removed.
 
This is how domestication and evolution works.  You have removed (selected
against) the orange marbles (genes), not allowing them to be replaced
(reproduced), which causes the percentage (gene frequency) of colored
marbles (genotypes) to change (shift), ultimately causing the color
(phenotype) of the jar to change (evolve).  Evolution and domestication
works exactly the same way because both result in a shift in gene
frequencies, causing changes in the animal.  Because natural selection
works in a highly dynamic environment, the real world, and because those
conditions change frequently, you cannot predict exactly how an animal may
evolve.  So, while a specific selectionist pressure is not random, the
combination of them result in a random effect.  That is the major
difference between domestication and natural selection; humans decide which
traits they like best for a particular purpose, so drive the evolution
towards a specific goal.
 
This is an important point in understanding the difference between
domestication and natural selection.  Every once in a while, you will hear
someone say some animal domesticated itself; this is often used to describe
the relationship between ancient wolves and stone age people, or even with
house mice.  Sorry, wrong.  It is true many animals have become quite
successful because of humans, either by making a living off our wastes, or
taking advantage of our disruption of the environment, but they are not
domesticated.  Their evolution was not human directed, but selected for by
non-human agencies.  In this case, natural forces selected for those
individuals what were able to exploit a human environment.
 
One last point that is very important.  Large populations have a tremendous
stability in their gene frequencies, which means they don't seem to change,
or evolve, even over very long periods of time.  Remember the pickle jar
fill of marbles?  Now imagine it is an olympic-sized swimming pool.  Even
if you worked all day removing orange marbles, how long would it take for
the pool to start looking blue-green?  The larger the population, the more
stable the gene frequencies, and the slower the "evolution." Because of
this, new species rarely develop from large populations; speciation occurs
in small and isolated populations, which is exactly the same thing that
occurs with domestication.  Almost all new species, either domesticated or
naturally-selected, stem from small and inbred populations.
 
Bob C and 19 MO House weasels (In Memory of Simon)
[Posted in FML issue 2383]