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From:
Richard Cryberg <[log in to unmask]>
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Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Mon, 8 Jun 2015 06:34:02 -0700
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"except for the past century which doesn't  even constitute a blip on the evolutionary radar."

The time scale for meaningful evolution is not so easy to define.  One of my other sicknesses is a life long interest in the genetics of domestic pigeons.  Pigeons likely were the second domestic animal after dogs.  Or third after dogs and cats.  Pigeons were domesticated some 5000 to 10,000 years ago.  Let me just take one single genetic example as to what man has accomplished in that time.  Man that by the way knew nothing at all about genetics, he simply knew if you mated what you like to what you like you got more of the same and sometimes even better.

Pigeons have a vast range of head feather decorations.  One of the most common is called a peak crest and is like the crest on a blue jay, a cardinal or a titmouse.  This is the result of rotating the feathers in the folicles towards the center line on the back of the head.  We know it is a single base error in a particular gene.  All pigeons that have feather ornaments on the backs of their heads have this mutant homozygous.  The next step up is a narrow shell crest where the peak has been broadened out so the feather rotation happens the width of the back of the head.  The next step up is a wide shell that extends from ear to ear.  The next step up adds in a feather length mutant that increases feather length from 5/8 inch to 1 1/8 inch.  The next step adds swirls at the ends of the shell.  Then another feather length mutant.  Followed by one or two more feather length mutants that all together give a bird with crest feathers that are so long they
 extend forward covering the whole side of the head so the bird can only see directly forwards.  Some of these exaggerated length feathers that started out in wild type at 5/8" are now 2" or 3" long.

The genetics are impossibly complex from a classic breeding standpoint.  All the added mutants require homozygous peak crest and are phenotypically invisible even when homozygous in the absence of homozygous peak.  Such mutants that only express in the presence of another mutant different from wild type are called supplementary mutants.  The point is man, simply by selective breeding over a few thousand years time has stacked up six or eight mutants on top of peak to get the most extreme crest.  Man that simply bred best to best.  And during that time period enough mutants happened along the way to allow man to do such selection.  It is possible some of these mutants existed in wild populations before selection by man and all man did was combine them by accident.  The genome is loaded with mutations that are phenotypically silent most of the time.  It is probable that some of these mutants are in control or switch regions as opposed to protein coding
 regions.  Control and switch mutations are quite common and often produce remarkable changes in phenotype while still allowing the gene to perform its normal function adequately or even fully.

Nature is typically a lot slower.  Nature can not afford to discard over 90% of each generation to move in a desired direction or the result would be extinction.  Nature also can not be nearly as selective in mate choice as man can be.  So, given the above example, if a very large crest were good for survival in nature it could well take a few million or more years for it to develop naturally versus perhaps 5,000 of part time selection by man.  Without GMO man can speed evolution by factors of hundreds or thousands.

Varroa is now about 20 years old in the US.  In another 20 or 40 or 60 years I am sure our bees will have undergone enough genetic selection that varroa will no longer be the major problem it is today.  Mans selective breeding programs will make it happen.  The back to nature crowd will likely be as opposed to such selection as they are to chemical control of varroa viewing both as unnatural.

Dick


" Any discovery made by the human mind can be explained in its essentials to the curious learner."  Professor Benjamin Schumacher talking about teaching quantum mechanics to non scientists.   "For every complex problem there is a solution which is simple, neat and wrong."  H. L. Mencken

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