Inbreeding VS Evolution

It would depend very much on the variation in the gene pool of your initial breeding population. There is some evidence from conservationists in Africa that elephants with reduced or no tusks are becoming more frequent but I'm not sure if this is much better than mere anecdotal evidence, it has certainly only had limited coverage in the general scientific literature. I think that given the time and a suitable size and variety in the initial breeding population you could produce a dramatic morphological range in elephants.Dogs are not the only example of extensive artificial selection. Cats. certain species of bird and of course a wide variety of plants both for food and for aesthetic reasons and a number of domesticated farm animals have been subjected to intensive artififial selection. Admittedly not all of them show as wide a range as the dog.Homozygosity means having the same allele, an organism displaying the phenotype for a recessive trait will normally be homozygous for that trait. In the context of a population I was proposing a population all of which had the same allele for a trait.

Zealot,

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Try just to see it from a leyman point of view (PS: that is someone that doesn't know what 'homozygosity' mean)

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No matter whose point of view we use, the answer is the same: variation and selection create diversity. There have been lots of discussions here about the pitfalls of using dogs as an example of speciation, since the results of isolated breeding events are not characteristic of population genetics in the general sense. These results point to the scope of variation that natural selection can act upon, but artificial selection (i.e. breeding) keeps variants that are not 'fit' except in the context of dog show aesthetics.What is the point of view at work in starting a thread dedicated to pitting selective breeding against evolution in general? How is it that you've decided that breeding has nothing to do with evolution when they both depend on variation and selection?------------------
En la tierra de ciegos, el tuerto es el Rey.

Well, having a look at animals that are forced to inbreed forinstance (famine, isolation etc), I cant help but think it would be entirely possible for them to change physical characteristics (bone structure for one) based on the effects of inbreeding. By that I mean I might have in me the genetic material (call it mutated genes)for example to produce hairy or not hairy offspring. Should hairy offspring be beneficial and much more likely to reproduce (say its cold) through natural selection, it really wouldn't take long before my offspring are all hairy. This however would only rely on have to rely on past 'mutations', not any new mutations. Well, I'm trying to understanda)How we can depend on fossils as clear examples of 'evolution' or mutation (I always associate evolution with mutation btw.. sorry), when we could produce the results by selective breeding. By this I take the example of an ape man mutating. There wouldn't actually have to be an 'active' mutation for the one to transform into the next.b) I'm trying to see how an evolutionist would be able to disagree with the creationist view (or the one I heard). By this I mean in theory, should we believe that a God created a variety of species with diverse genes, it would be possible for animals to change characteristics based not on mutation, but selective breeding (especialy inbreeding). This goes especially if we believe that every gene in a organism is essentially a 'mutation' from another gene ?Assume that a we placed every creature (with a diverse selection of genes) on Mars forinstance (or an Earth replica), then it would not actually be neccesary for any of the animals to mutate to facilitate a visible change in characteristics, it would merely take natural selection surely ?thanks for your input.

Zealot,

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I might have in me the genetic material (call it mutated genes)for example to produce hairy or not hairy offspring. Should hairy offspring be beneficial and much more likely to reproduce (say its cold) through natural selection, it really wouldn't take long before my offspring are all hairy. This however would only rely on have to rely on past 'mutations', not any new mutations.

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But the variation wouldn't stop there. In every generation there would be variation among the offspring, and random mutations would occur to widen the scope of the variation. Why do you think that there would be a point where no further change (such as new mutations) would occur?

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How [can we] depend on fossils as clear examples of 'evolution' or mutation (I always associate evolution with mutation btw.. sorry), when we could produce the results by selective breeding.

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Like I've said, the principle involved is the same: selection acting on variation. What is breeding except high-speed evolution? The fact that we observe the process is actually evidence in favor of evolution.Why do you have the notion that breeding processes somehow invalidate evolution? The opposite is actually true.------------------
En la tierra de ciegos, el tuerto es el Rey.

Your hypothetical scenario seems considerably different from normal creationist approaches. For a start you would require a large initial breeding population, which certainly isn't consistent with a literal interpretation of the bible.If your creationism is broad enough to encompass such radical deviations then you might as well go straight on to asking how we can be sure God didn't just create the whole universe yesterday.

Hi, Zealot! It seems that you're asking why mutation is necessary to the theory of evolution, and whether what we observe couldn't be explained by pre-existing variation.As has already been pointed out, since the flood reduced the breeding population of all land-based species dramatically to a maximum of seven pairs, the initial variation in your breeding populations would be exceedingly small and could in no way account for the diversity we observe today.What's more, mutations are inevitable. At the genetic level the reproductive process is error prone. Mutations, which are just copying errors, will almost always happen. For example, if a genome has a million base pairs and if the odds of a simple single-base-pair copying error is 1 in a hundred thousand, then how often will it happen that the genome is copied with no errors during reproduction? The odds of this happening are 0.0000454%. In other words, 99.99546% of the time there will be at least one copying error during reproduction. You simply can't discard mutation as an evolutionary force.--Percy

Man I love having to reply to 3 posts at once! I'm Not saying there wouldn't be new mutations, only that it wouldn't be neccesary for new mutations to occur for more different offspring to appear. Genetic diversification would not be neccesary to continue different bone structure for instance. Hypothetical.. a Labrador (from a wolf) is the result of natural selection by 'human' interferance , and then from that labrador we produce a dalmation ect ect. There doesn't have to be an actual mutation, merely a dormant gene from the wolf ancestor. Well, I thought the process of evolution is dependant on an actual gene mutation resulting directly in an organism to obtain an immediate benefit and in doing so passing its genetic material onto its offspring, which will also gain this advantage, hence survival of the fittest ?I'm not saying the breeding process invalidates 'mutation evolution' merely that if we could achieve similar structural changed in an organism by selective breeding, it would really negate the need for an active mutation to change the shape of a species.

Hi, I'm not really arguing the creationist stance, since I dont really even know or understand it fully! From the little I understand, I believed that each creature was endowed with a sufficient diversity of gene's to produce different looking children.
I dont know, thats why I wanted to know how many significant mutations there have been in the human history over the last 60 000 years. From what I recall hearing , there was suppose to be a bottleneck about 60 000 years ago, so I am curious as to how great a role mutations play.home time! cheers

Zealot,

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I'm not saying the breeding process invalidates 'mutation evolution' merely that if we could achieve similar structural changed in an organism by selective breeding, it would really negate the need for an active mutation to change the shape of a species.

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You're missing the point. Either way it's variation and selection. What difference would it make if you could 'negate the need' for new mutations when it's observed that these new mutations occur all the time?Offspring vary from the parent, and vary among each other. New mutations add to this variation, and selection keeps the best adapted variants. The cumulative effect of billions of years of this process is the diversity we see in nature today.------------------
En la tierra de ciegos, el tuerto es el Rey.

Hi Zealot! I thought people had already confirmed this for you, but you are correct that mutation is not essential for creating new breeds through selective breeding. It may even be possible, given sufficient numbers of generations, to create new species drawing only upon existing variation. This is mostly correct. The only part I'd question is that about "immediate benefit." Mutations can take a long time before they are expressed in some way and affect a descendent organism.For example, let's say you have a population of animals with two alleles for eye color. An allele is a variation of a specific gene. Let's say the two alleles for the eye color gene are for brown eyes and for black eyes. Every animal in the population has either brown eyes or black eyes.Let's say that the black allele is dominant so that an animal has to have two copies of the brown gene in order to have brown eyes. Any other combination of one brown allele and one black allele, or of two black alleles, results in black eyes.During reproduction a copying error occurs yielding a third allele for the eye color gene, an allele for green eyes. Let's say the allele is not dominant, but instead is recessive with respect to both the black and brown alleles. That means that the newborn animal has one green allele, and one black or brown allele, and its eyes will be black or brown. It will contribute its black or brown allele to half its offspring, and its green allele to the other half. In other words, half its offspring will have one green allele, and their eyes will be black or brown since green is recessive. But if these offspring should mate with each other, then 25% of their offspring will have two copies of the green allele and will therefore have green eyes. In other words, it takes two generations for a non-dominate mutation to become expressed in the population.I said all this because you said, "...resulting directly in an organism to obtain an immediate benefit..." As you can see, there is nothing direct or immediate about the process I just described. And this is a simple case. Often genes do not have a simple dominant/recessive relationship but something far more complicated involving other genes, possibly many other genes, and triggers for turning these genes on and off. And a mutation could occur in a non-active region of the genome (colloquially known as junk DNA), thereby having no effect whatsoever, or at least not until a future mutation activates the region. In other words, it could take generations and generations before a mutation expresses itself overtly. And in the meantime, new mutations continue to occur and accumulate in each generation. When a breeder thinks a newborn is so different from its parents that it could only be due to a new mutation he is probably wrong - given the huge number of unexpressed old mutations resident in every organism, it is most likely an old mutation that was somehow finally visibly expressed.It makes perfect sense, as an aide to understanding, to simplying things by removing consideration of mutations, but you cannot realistically remove mutation as an important force in evolution.--Percy

(Phenotype is the word for the physical expression of the genes, that is to say, the physical form of the individual.)Well, that's almost impossible to determine. Consider an individual born with a mutation that isn't fatal or detrimental. You're looking at it right after it was born. Let's say you even know exactly what the mutation does, because it's caused some observable physical effect. How do you determine whether or not it's a beneficial mutation? There's no way to know if the mutation is useful or not until the individual reproduces, because "beneficial" has to be taken in relation to the environment the individual inhabits and is determined by whether or not the individuals with the mutation tend to leave more survivng offspring.It's not like we have a meter that we can point at a mutation and see if it's beneficial or not. Sometimes mutations can be both harmful and beneficial, like sickle cell anemia in humans. It all depends on environment.

Percy brought up the point that you start from a mixed genetic background and end up with your breeds. This is exactly what happens and the mouse as a genetics model developed just this way....like dog breeds, there were mouse breeds. These were donated to the Jackson lab which then went on to make inbred lines of mice selecting for various traits. The entire project is to take as much variation away to look at the genetic basis of specific traits. The difficulty is that variation due to mutation is constantly popping up whether you want it to or not...in any case, dog breeds are far more complicated as to their origin and it they probably have a polyphyletic origin i.e. no one stock...a references on dog evolution....Science. 2002 Nov 22;298(5598):1613-6. Related Articles, LinksComment in:
Heredity. 2003 Mar;90(3):201-2.
Science. 2002 Nov 22;298(5598):1540-2.Ancient DNA evidence for Old World origin of New World dogs.Leonard JA, Wayne RK, Wheeler J, Valadez R, Guillen S, Vila C.Department of Organismic Biology, Ecology and Evolution, University of California, Los Angeles, CA 90095-1606, USA. Leonard.Jennifer@NMNH.SI.eduMitochondrial DNA sequences isolated from ancient dog remains from Latin America and Alaska showed that native American dogs originated from multiple Old World lineages of dogs that accompanied late Pleistocene humans across the Bering Strait. One clade of dog sequences was unique to the New World, which is consistent with a period of geographic isolation. This unique clade was absent from a large sample of modern dogs, which implies that European colonists systematically discouraged the breeding of native American dogs.

I am trying to imagine the full range of morphology created by dog breeders, and compare it to some other group of animals divesifying in the wild. Everybody imagine with me !Okay, I see dogs, chihuahuas, dachshund, German shepherd, St Bernard, etc.On the other side I see the whole variation of apes...We got the gorilla, black and large; on the other side there are large dogs, and black dogs...We got the orangutan, red long hairs; there are long-haired dogs also.We see lively, intelligent chimps; dogs got that version too.And there is the naked, short-faced human; and there are naked dogs, and short-faced dogs!Okay, from this thought experiment I can appreciate the potential for change. If dogs can diversify that much, it is reasonable to say that apes can do the same, and one became human.

But I thought that the problematical point was supposed to be that the dogs all show this variation within one interfertile species, whereas the primates you covered represent different species.