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Thread: Tale of Two Breeders

  1. #1 Tale of Two Breeders 
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    Two breeders, Paul and Mary, each purchased a mating pair of thoroughbred animals.
    Paul wants to breed them and sell the offspring. He wants to Preserve the characteristics.
    Mary wants to develop a new breed. She wants to Modify the legs to be longer.

    Let’s say we check the genes for leg length in the four animals and find this:
    Pauls male: 115 and 120
    Paul’s female: 108 and 112
    Mary’s male: 116 and 118
    Mary’s female: 110 and 113

    Paul has confidence that breeding his and similar animals will assure that the leg size stays in that range; his animals will continue to get blue ribbons and he'll make profits.

    But how does Mary breed her animals so that the leg size increases by 7%?

    One method is suggested in a Nova video (see below).
    Is that the only method?
    And isn’t that the same as giraffes eating from taller trees?

    “RAY COPPINGER: Nobody had to know about a long nose or long legs. All they had to do was take the dog out there in the desert and have it chase rabbits. Over the generations of just picking the best dog, the one that can see the rabbits best, the one that can catch the rabbits, what they do is, they get longer legs. They didn't breed for longer legs, they just favored those dogs that had them.”
    Transcript from Nova program “Dogs and More Dogs” PBS Airdate: February 3, 2004
    http://www.pbs.org/wgbh/nova/transcripts/3103_dogs.html


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  3. #2  
    Forum Cosmic Wizard icewendigo's Avatar
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    Select dogs with longer legs.


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    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    The NOVA video isn't proposing Lamarckism.

    They are merely saying that breeders who selected for rabbit hunting ability indirectly selected for longer legs.
    "I almost went to bed
    without remembering
    the four white violets
    I put in the button-hole
    of your green sweater

    and how i kissed you then
    and you kissed me
    shy as though I'd
    never been your lover "
    - Leonard Cohen
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  5. #4  
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    Quote Originally Posted by icewendigo
    Select dogs with longer legs.
    Mary's starting point:
    male: 116 and 118
    female: 110 and 113

    She wants males with 124-126 range.

    What's the first step?

    If her animals are the origin of an isolated population, what's the chance of their getting longer legs if they want to catch rabbits?
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  6. #5  
    Time Lord Paleoichneum's Avatar
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    Quote Originally Posted by gs99
    Quote Originally Posted by icewendigo
    Select dogs with longer legs.
    Mary's starting point:
    male: 116 and 118
    female: 110 and 113

    She wants males with 124-126 range.

    What's the first step?

    If her animals are the origin of an isolated population, what's the chance of their getting longer legs if they want to catch rabbits?
    Natural variation will occur within the offspring, so the first step is to breed and see which of the foals have the longest legs, then breed them with stock from Paul who also have the longest legs, repeat the cycle...
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    Paul wants to preserve the original leg length of his group; he does not want to be involved with Mary's project.

    But let's say Mary purchased another set of animals with similar genes as her first, but with slightly longer legs.
    The male population now has a genetic variety of 116, 117, 118, and 119.
    The female population has 110, 111, 113, and 114.
    (The male has longer legs in this species.)

    She breeds the longest male legs (119) with the longest female legs (114).

    But how many generations are needed to get longer legs?

    The only food source on this island are fast rabbits.
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  8. #7  
    Time Lord Paleoichneum's Avatar
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    Quote Originally Posted by gs99
    Paul wants to preserve the original leg length of his group; he does not want to be involved with Mary's project.

    But let's say Mary purchased another set of animals with similar genes as her first, but with slightly longer legs.
    The male population now has a genetic variety of 116, 117, 118, and 119.
    The female population has 110, 111, 113, and 114.
    (The male has longer legs in this species.)

    She breeds the longest male legs (119) with the longest female legs (114).

    But how many generations are needed to get longer legs?

    The only food source on this island are fast rabbits.
    My initial comment still stands.

    The "genetic variety" will change with each generation due to the natural course of mating. She will have to bring in more animals if she wants to avoid too much inbreeding though.
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    Quote Originally Posted by Paleoichneum
    The "genetic variety" will change with each generation due to the natural course of mating.
    Mary knows that.
    But she is not interested in normal "genetic variety".
    She wants to modify it, to get longer variety.

    Let's say she gets new stock every so often to prevent inbreeding problems.
    But the maximum leg size is "119".

    How can Mary's animals get longer legs to overcome their prey?
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  10. #9  
    Veracity Vigilante inow's Avatar
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    Quote Originally Posted by gs99
    Let's say she gets new stock every so often to prevent inbreeding problems.
    But the maximum leg size is "119".

    How can Mary's animals get longer legs to overcome their prey?
    How is that maximum leg size constraint implemented? There will be some offspring with mutations causing their legs to be longer than 119, so why do you set such a false ceiling? What's your logic there?
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    Forum Cosmic Wizard icewendigo's Avatar
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    If you insure that selected dogs live by providing food etc and mate, and systematically select longer legs, the variation will progresivley be displaced towards longer and longer legs, you will eventually end up with animals that have girafe long legs that most probably could not survive in the wild.


    (This would not occur in the wild because a multitude of other factors would outweigh the specific advantages of longer legs (resistance to starvation/cold/heat/disease, mating/fertility, sight/sensory, digestion, metabolism, healing, stamina, etc, etc, etc), and changes in the environement can make a trait that is previously advantageous less advantageous than some other trait that was not all that advantageous or that might even have been disadvantagous before).
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  12. #11  
    Time Lord Paleoichneum's Avatar
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    Quote Originally Posted by gs99
    Quote Originally Posted by Paleoichneum
    The "genetic variety" will change with each generation due to the natural course of mating.
    Mary knows that.
    But she is not interested in normal "genetic variety".
    She wants to modify it, to get longer variety.

    Let's say she gets new stock every so often to prevent inbreeding problems.
    But the maximum leg size is "119".

    How can Mary's animals get longer legs to overcome their prey?
    Apparently Mary does not understand genetics that well. There is no such thing as "normal" and "longer" genetics in the sense you seem to be using the terms. Mutations will naturally occur in each generation of offspring that may result in, among other things, longer legs then the parents had.

    I will repeat inow's question. What exactly are you looking for? As it doesn't seem to be related to how genetic works.
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    What exactly are you looking for?
    I’m trying to explain how evolution works by following a simple trait in artificial selection by two fictional breeders.

    There is no such thing as "normal"
    When they started their projects, Paul and Mary were told that male blue-ribbon winners had leg size 115-120. They arbitrarily called this “normal”.
    Paul’s objective was to maintain offspring in this “normal” genetic range, to sell offspring.
    Mary’s objective was to generate a new breed, starting with longer leg size.

    How is that maximum leg size constraint implemented?
    The maximum leg size of all specimens Mary obtained was 119.

    "Every [animal] gets one copy of every gene from mom and one from dad. These genes can be mixed and matched in countless ways, but if the parents don't have it, the pup can't get it.” - Nova, Dogs and More Dogs
    Then, if the parents don’t have size greater than 119, the pups can’t get it.

    There will be some offspring with mutations causing their legs to be longer than 119
    Is mutation the only way to introduce NEW genetic variation (e.g. longer legs)?

    Random mutations cannot be “ordered” by the organism or the population.
    What are the odds of a “120-size gene mutation” occurring in a germ cell that happens to get involved in a gamete that lives to reproduce? And then, isn’t it possible that the spouse’s gene may be the one actually expressed?

    This seems to be very “undependable” for Mary, wanting to make profits in her lifetime.

    How do random mutations cause new genetic variation to be selected so that an organism can adapt and survive a certain problem? Flowers get bigger, need longer beaks. Nuts get bigger, need stronger beaks.

    Mutations will naturally occur in each generation of offspring that may result in, among other things, longer legs then the parents had.
    Are there reports showing the rate of mutations? It would be helpful to quantify this.
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  14. #13  
    Veracity Vigilante inow's Avatar
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    Quote Originally Posted by gs99
    How is that maximum leg size constraint implemented?
    The maximum leg size of all specimens Mary obtained was 119.
    First, you've managed to merely repeat yourself without every answering my question. Second, you seem to be working with a version of evolution which has little resemblance to reality.


    Quote Originally Posted by gs99
    "Every [animal] gets one copy of every gene from mom and one from dad. These genes can be mixed and matched in countless ways, but if the parents don't have it, the pup can't get it.” - Nova, Dogs and More Dogs
    Then, if the parents don’t have size greater than 119, the pups can’t get it.
    Sorry, wrong. Ever heard of a mutation?


    Quote Originally Posted by gs99
    There will be some offspring with mutations causing their legs to be longer than 119
    Is mutation the only way to introduce NEW genetic variation (e.g. longer legs)?
    Of course not. You could cut the leg with a saw, insert a block of wood, and sew it back together. Good grief, man... You're arguing against something you clearly need to study more and better.

    Your post showed a level of misunderstanding so profound that I'm not quite sure where to begin, so I won't.
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  15. #14  
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    Quote Originally Posted by inow
    Your post showed a level of misunderstanding so profound that I'm not quite sure where to begin, so I won't.
    Perhaps, I hope, later you will think of something.
    A good teacher or negotiator will find a way.

    Why all the criticism? I'm not a professional biologist and don't know all the buzzwords. But I provided information clearly enough for anyone to understand the questions.

    I tried to describe a situation to explain basic genetics and selection.
    If I can't explain it, I don't understand it.

    Does anyone know of books that describe techniques of artificial selection (breeding)? I'm curious how both Paul and especially Mary need to be aware of mutations.

    It seems that there is a lot of misunderstanding about this subject.
    For example, if Nova is wrong about their statement, why don't they edit it?

    What I get from your post:
    New genetic variety (what is needed for adaptation and survival) is introduced by mutation only.
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  16. #15  
    Universal Mind John Galt's Avatar
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    Quote Originally Posted by gs99
    A good teacher or negotiator will find a way..
    Arguably there is also a need for a willing student. You seem to fit the bill.
    I think the hostility you have sensed may be because some of your misunderstandings had the look and feel of a creationist trying to be clever and sneek some nonsense into a discussion that he could then ridicule.

    Quote Originally Posted by gs99
    Why all the criticism? I'm not a professional biologist and don't know all the buzzwords.
    It may have helped if you had explained why you were setting up the thought experiment.


    Quote Originally Posted by gs99
    But I provided information clearly enough for anyone to understand the questions.
    Subsequent events suggest this was not the case.

    Quote Originally Posted by gs99
    Does anyone know of books that describe techniques of artificial selection (breeding)?
    Well, two rather seminal works are Origin of the Species, where Darwin devotes the first chapter, Variation Under Domestication, to the breeding of animals; and the English translation of Gregor Mendel's work on peas that founded the science of genetics.

    I'm curious how both Paul and especially Mary need to be aware of mutations.
    They require no knowledge of these at all.

    For example, if Nova is wrong about their statement, why don't they edit it?
    You need to distinguish between science and popular science media that, though they inform, lean strongly towards entertainment. These are necessarily simplified, dumbed down and sometimes grossly inaccurate.

    New genetic variety (what is needed for adaptation and survival) is introduced by mutation only.
    Correct.
    However, old genetic variety may be present and not expressed at present.
    Phenotypic variations in your example might permit more than the 119 cm length.
    And probably five other exceptions that should be noted for comprehensive comment, that I am wholly ignorant of.
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  17. #16  
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    Quote Originally Posted by John Galt
    Quote Originally Posted by gs99
    I'm curious how both Paul and especially Mary need to be aware of mutations.
    They require no knowledge of these at all.
    It seems that mutations are involved/needed to create new breeds, and species.
    Why wouldn't Mary need to understand how they work?

    Thanks for your suggestions on books; I'll review those.
    But I'm interested in (lower) levels of operation these authors were unaware of, I think.
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  18. #17  
    Time Lord Paleoichneum's Avatar
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    Quote Originally Posted by gs99
    Quote Originally Posted by John Galt
    Quote Originally Posted by gs99
    I'm curious how both Paul and especially Mary need to be aware of mutations.
    They require no knowledge of these at all.
    It seems that mutations are involved/needed to create new breeds, and species.
    Why wouldn't Mary need to understand how they work?

    Thanks for your suggestions on books; I'll review those.
    But I'm interested in (lower) levels of operation these authors were unaware of, I think.
    Not really. humans had been domesticating and selecting for specific traits centuries before any understanding of the processes involved were known. I the example you are using here you are over-complicating the knowledge needed for Paul and Mary to accomplish their goals.

    All Paul needs to do is simply select the individuals from each generation that show outwardly the traits desired and breed them.

    Same for Mary, all she needs to do is select the individuals that have longest legs and breed them. If she is lucky it will only take a couple generations to meet her goal. If not she may have to breed several dozen generations or more.
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