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Improving the Species

NPR Talk of the Nation Science Friday had a feature about how hunting and fishing rapidly affect the evolution of the species in question in a negative way, since hunters and fishermen like to take the big fish or animals.    Well bang the drum.  How obvious is that?   In forestry, we see that in high grading/selective cutting, when people cut out only the biggest trees.    The young man did a good job of describing the problem, but the program in general did a bad job of prescribing a solution.

Cave painting of ancient aurochs

Nature is profligate.   That is the basic assumption of evolutionary theory.    Many more individuals are  born than can survive.   Human activities rapidly select for particular characteristics and we have been doing it for a long time.    That is why a miniature poodle doesn’t much look like a wolf or a cow has only passing resemblance to aurochs.  (The last recorded wild auroch, BTW, died in Poland 1627.) 

Game keepers and river keepers have long recognized the problem with taking the biggest and best and leaving the runts to reproduce.   The same goes for forestry.    The way to go about managing for this is to make sure you take out the undesirable traits too, or in greater numbers.  

It requires more work and understanding.  In forestry, for example, the biggest trees are not always the oldest.   You have to harvest the small ones too or maybe even more.    Down on my tree farms, the hunters are members of Quality Deer Management association.   Fortunately, their task of improving the deer herd is made much easier by the deer population explosion.    In the case of deer, for example, the worst thing you can do for the health of the herd is to limit hunting. 

Not all species are as common as deer, but some of the same management principles apply.   You don’t improve the total herd/forest/school by protecting all individuals equally.   In a wild population, you are probably looking to increase genetic diversity.   This makes the species more robust.   Remembering the nature if profligate maxim, you might improve the genetic diversity AND in the long run the numbers of a species by disproportionately eliminating individuals with particular sets of characteristics.   This creates room for the others.   

When dealing with the natural world, many things seem counter-intuitive.


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Comments

Predators have always applied selective pressure to prey. There is nothing new here. In some cases it may be an advantage for the prey to be bigger, rather than smaller, as it then has more chance of defending itself. This applies to deer and cats, for instance.

Where there is a problem with human fishing is that we over-fish, and we damage the whole ocean floor.

No, you would not increase genetic diversity by reducing the population or selecting out certain genetic variants. Genetic diversity tends to be greatest when a large population is increasing - i.e. selective pressures are light.
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Don - it depends on the populations. If you have some isolated populations, of differing numbers, it might make sense to reduce the larger population.

Re a forestry example. If you want to improve your oak forest after it has been selectively cut for too many years, you will probably want to clear cut some areas to get rid of the runts and allow infill by better trees.

Commercial fishing is a problem for the reasons you mention. I am thinking mostly of deer. We have a population explosion of deer. We can increase the quality of the deer herd by shooting more, especially does and smaller individuals.

"We can increase the quality of the deer herd by shooting more, especially does and smaller individuals."

Indeed, but then you are defining "quality" by some human preference. This is to treat the deer as a domestic animal, where you "improve the breed" by artificial selection.
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As you said in the earlier post, all predators select. That is, in fact, an imporant basis of natural selection. If we just take the best, we will select for sick and weak. I don't think that is a good idea. Somebody or something has to kill deer. If we reintroduced predators, they would tend to select in a way quality deer management would do. Of course, in densely populated places like Virginia, we cannot reintroduce cougars and probably not even wolves. The coyotes and bobcats cannot take down many deer, so we are left with hunting.

There are way too many deer on the land. We have seen their numbers explode in the last decades. In some places they are serious threats to forest health and natural regeneration. We will have to increase the numbers of deer harvested each season. We may as well select for health and fitness, rather than just let it be taken over by random chance.

The problem we will have soon is that the numbers of hunters are declining. Soon we may have to pay people to do what people now pay to do. Hunters and hunting fees are the most important force for wildlife conservation. I am afraid what might happen when/if that it lost.

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