Adverse Long-Term Effects of Artificial Selection

Okay, this is my attempt to reframe my first topic in a way that will get people actually talking about the topic, and not irrational numbers. This is a link to the first attempt at the topic that went horribly wrong. At least, it should be if I've got the hang of this HTML stuff...The Problem With Intelligence?I’m very happy that Adminnemooseus thought the topic was worthy of pursuing. I hope it can live up to his/her expectations! Without further adoArtificial selection. It’s not like natural selection: The Meat-Grinder That Grinds Wherever There’s Meat. In contrast, artificial selection is directed by collective human ingenuity and sometimes delightfully arbitrary cultural whims. It has given us the domestic dog, modern barley, and for some strange reason has made the orange carrot ubiquitousIt has proved a very powerful tool, and I wouldn’t be surprised if it has been part of humanity’s bag of tricks since we first properly got the hang of living together and talking about stuff. However, artificial selection as we have practiced it for thousands of years has inherent problems that have only recently come to our attention, since we have become slightly less ignorant of genetics.Firstly, (until the last few years,) we could only select for traits that we could detect with our senses, so the threat of guerrilla-style genetic sabotage taking place alongside a visible improvement was ever-present (hence wheezy, sad looking animals that have been thoroughbred to within an inch of their lives).Secondly, before we had an understanding of natural selection, we didn’t realise the karmic whirlwind we could reap through systematic culling. Vaingloriously, we thought we were improving the world for all when we went about systematically killing (for example) rattlesnakes every time we heard them rattle. Except we weren’t, because we were unwittingly carrying out a selective breeding program to create mute rattlesnakes who don’t give any warning at all before they sank their fangs into us. Similarly, our overuse of antibiotics (which are A Good Thing on the whole) has, through the selection mechanism, consequently begun to foster resistant bacteria.I can imagine creationists going Aha! just goes to show you that it takes a REAL intelligence to modify organisms. But I think that’s a bit cheap, especially because its quite clear that artificial selection, for the reasons that I have described, is a much less powerful force than natural selection, which selects for the genuinely best rather than the apparently best.So why am I writing about the apparent problems of artificial selection? Well, I wonder if anyone will take issue with my idea about the two problematical aspects of artificial selection, or (oh joy!) help to refine and add to them.I think more generally I want this is a topic about the differences between artificial and natural selection. Yes, in a way, its all just selection, and the distinction between them is a bit artificial. But somehow I think there is something actually rather special and strange about artificial selection that is worthy of our exploration.Thanks!

Thread moved here from the Proposed New Topics forum.

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I can imagine creationists going "Aha!" just goes to show you that it takes a REAL intelligence to modify organisms. But I think that's a bit cheap, especially because its quite clear that artificial selection, for the reasons that I have described, is a much less powerful force than natural selection, which selects for the genuinely best rather than the apparently best.

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I disagree. What about sexual selection in birds such as the peacock, in which females prefer males who have extremely long tails? These tails waste energy that the male could use to get more food, escape predators, or whatever else peacocks do.Natural selection has bred these birds to do well enough to survive. Artificial selection could be used to breed peacocks with even longer tails, or other characteristics, to the extent that they would be unable to survive in the wild. Therefore, I think that artificial selection is more powerful force and can usually change organisms faster than natural selection.

What point exactly is it that you are disagreeing with? One of the major ideas in sexual selection theories is the fact that these problematic display features, such as the peacocks tail, are in fact detrimental and consequently the fact that the animal survives with such a detrimental feauture shows that it must have some traits which increase its ability to survive and counterbalance the negative effects of the tail. The sum of the -ve effects of the tail and the +ve effects of other traits is what is effectively being selected.Meanwhile in a purely artificially selective human driven situtation many selective pressures are removed from the organisms being selected and selection is on one or more traits almost arbitrarily selected by the human directing it, efforts may in fact be made to overcome fitness problems in an organism with a particularly good example of a specific trait allowing large amounts of detrimental traits to be propagated which might naturally be selected out.The question wasn't really whether natural or artificial selection were more powerful in terms of driving a trait in a population to a specific endpoint in the fastest time, but whether it was a more refined and powerful tool in its ability to sum all the various factors acting upon the organism while artificial selection acts in the crudest possible manner selecting for at best only a few traits leaving the rest of the organisms genetic profile to struggle along as best it can.While the change from artificial selection may be faster it is also much cruder and perhaps more prone to unforseen and detrimental side-effects. Of course there is no theoretical reason why a selective pressure couldn't be so strong as to rapidly drive a population towards a specific point in the fitness landscape through natural selection, but I suspect that in the wild this would be far more likely to lead to extinction of the population, a factor which mankinds alleviation of many selective pressures can counteract.I may have misinterpreted the thrust of the opening post, but that was how I read it.TTFN,WKThis message has been edited by Wounded King, 10-17-2004 09:47 AM

Okay. I'm not really informed about artificial selection, and I'm just speculating about it in the hope that someone is going to help me out with it. (But maybe it would be best if I just read something about it. Curses.)I'm not sure if you got what I was saying. From your peacock-themed response, you seemed to be arguing that artificial selection is in some ways a more powerful tool than natural selection. My first response to this is that if we want to do something with an animal, then the ONLY tool that we have at our disposal is artificial selection. We aren't going to do anything through natural selection.But I don't think you meant that. Maybe you meant that artificial selection is more powerful because it can get things done quicker than can natural selection. I think that's probably true, although I guess it depends largely which creature you are talking about -- and I'm not sure how you'd make the comparison.Or maybe you meant that we can create things through artificial selection that won't survive in the wild; therefore, artificial selection is a more powerful force. That's true to a certain extent, but although artificial selection is better able to produce variety in the short-term, it doesn't have the long-term ability to create and sustain species like natural selection. Or at least, I think that's what the mindboggling variety of the fossil record demonstrates. The fact that we could support a managery of weird and wonderful critters if we wanted says to me more about our excellent vetinarians and standard of living than about the ability of artificial selection to create viable beasties.When I said that I didn't think that it was as powerful, I meant that you can't keep pushing animals in weird directions indefinitely, and I was wondering why. In my first post, my contention was that if you are just selecting for the (say) longest tail in your peacocks, then there is a problem of diminishing returns. I was saying that a reason for this might be that you will also be collecting all kinds of other problems in your breeding group that have to be managed very carefully. But maybe that's wrong.Perhaps a hackneyed tortoise and hare analogy could be applied to natural and artificial selection respectively; maybe artificial selection can't REALLY change an organism. This is true for practical stuff (like the fact that you can only increase the yield of a tomato plant so far) and for sinister just-for-kicks stuff (there aren't any really monsterous peacock tails). If this wasn't the case, you can bet some silly bugger with too much time and money would have dogs the size of ants and horses the size of houses. And elephants ARE horses the size of houses (sort of); but they were brough about through natural selection, not artificial selection.But maybe that analogy doesn't hold up because the timescales for natural and artificial selection are so different. We don't have the millions of years neccessary to turn (for instance) a mongoose-like creature into a sperm whale. If there was a selective breeding program that went on for fifteen million years, then I bet you could do all kinds of great stuff. But artificial selection has, thus far in human history at least, all been pretty short term stuff in comparison.I don't think this is helping. My topic must be too vague. Maybe we should jettison all that stuff about unintended natural selection (rattlesnakes, MRSA), because that is either clouding the issue or not interesting people. If we have to really focus things, then want to talk about WHY there are limits to what artificial selection can accomplish. Is it purely just a time thing? Why do thoroughbred animals have a tendency to floppiness?

Yes - I think that's exactly what I meant. I'm want us to talk about the profound difference between a quick fix and a tested and trusted solution!

One point that I found especially interesting in the original (misplaced off-topic) version of this discussion, was the question "Could the near-eradication of a disease end up resulting in the breeding of a "super-disease"".In other words, would we be impossing artificial selection to create a "better" pathogen?Moose

Its my understanding that the overuse of antibiotics has indeed created tougher bugs through the same kind of inverse artificial selection that brought us ninja-assassin (well, silent) rattlesnakes.Tuberculosis, once easily seen off by antibiotics is back, and bigger than ever before. Loads of other bugs are gradually developing resistance too. And its all because we were smart enough to come up with antibiotics in the first place! It kind of makes me think of that red queen thing, of running to stay still.

You certainly might see selection for a 'better' pathogen, but I would say that it would be through natural rather than artificial selection.If you grow a culture of bugs on a Luria agar plate and then add ampicillin (Amp) you are clearly going to select for Amp resistance. This is clearly an artificial scenario as you are obviating many of the selective pressures operative in the wild by providing space and nutrition for the bugs. If you are simply treating someone with antibiotics then all you are doing is adding a further selective pressure to its normal environment.Therefore, you might see in culture an ampicillin resistance strategy evolve which would be inviable for the bugs in the wild because you have intervened to reduce the selective process as far as possible to being solely dependent on 1 factor.I don't think the interference of a human agency to introduce a selective pressure to the environment is sufficient merit the term 'artificial selection'.TTFN,WK

I would have to agree. The antibiotics could be seen as a novel environmental stress whereas an agar plate in an incubator is an artificial environment totally geared towards favoring growth and maintenance of bacteria.Creationists often seem to distinguish artificial and natural selection on mechanistic grounds i.e. that natural selection would never produce such variation or that artificial selection somehow reaches "limits". But mechanistically they work the same way, however artficial selection drives traits to fixation which do not necessarily make the organism more fit but rather are production or aesthetic oriented and require extra effort to maintain the traits i.e. British Bulldog birthing problems. Both forms of selection however, are changes in allele frequency over time.

Okay, I think I get what you're saying. Can you bear with me and clarify something? Are you saying that the rattleless-snake example and the "better bugs" example are not directly analogous? I thought they were. Or are you saying that the rattlesnake example isn't really an example of artificial selection either?The reason I ask is because I thought the rattlesnake tale (that I just realised I have now sited about a million times without actually chasing up even slightly) was actually a really nice example of a kind of artificial selection, albeit unintended. After all, isn't artificial selection just a way of discribing a selective pressure resulting from human influence? Are you saying that it isn't artificial selection if the consequences are unintended? From the many off-hand examples people have given so far, it seems that unintended consequence is something that is deeply seated in any artificial selection project (see persian cat breathing difficulties, etc, etc... ad nauseam). But in the cases of the rattlesnake and the bacteria the change is pretty much all unintended consequence from an eradication attempt.Does that make sense, or is this wabbit woofing up the wrong weeping willow?

I would say that this is definitely not the case. I wouldn't characterise your rattlesnakes as a case of artificial selection. As has been pointed out in artificial selection it is not simply the selection that is important but the obviation of other selective factors. Without this obviation, imagine if you will a situation where artificial selection only operates during the breeding period to prevent or promote certain matings, it is not clear to me how much more effective artificial selection would be.The unintended side-effects you mention, such as the birthing problems or breathing difficulties, are a result of the crudity of artificial selection. The rattle-less rattlesnake and antibiotic resistant bacteria are conversely the result of the power of natural selection.One possiblel way to tell the difference is to ignore the human factor, in terms of what we think of as a beneficial outcome regarding the organisms, in the equation and see if the organism is 'fitter' than it's ancestral type was in the same environment. If the answer is no then you are more likely looking at the effects of artificial selection.This no longer holds true if you allow many more steps in the evolutionary process as environmental changes may lead to a situation where an ancestral type might do better but the organism is locked into a certain system due to previous changes in its genetic make-up.TTFN,WK

Hi Mammuthus! I just tried to address the first part of your post in my response to the previous poster, so I'll just talk to you about the second half of your post.I think you're right -- I find the assertion that natural selection couldn't produce such variety as we witness in nature a bit funny, mainly because (indeed, sometimes don't even allow) the MASSIVE timescales involved. If we can get pomeranians from wolves in a few thousand years, why can't we get hump-back whales from wolf-like beasties in tens of millions? And of course, it is all just change in allele frequency over time, as you say, and a distinction between artificial and natural selection is IN A WAY not necessary, because its just the same mechanism in each case.However, I want to question the second thing that you mention; namely, that the idea of "limits" to artificial selection is questionable. I thought this was something that is observable. (Why don't we have dogs the size of ants? etc...) I'm NOT advancing some kind of creationist argument: saying that this demonstrates the limits that ANY kind of selection can play in influencing the appearance and genetic makeup of an organism. I think that artificial and natural selection are sufficiently different to mean that any limitations to change through artificial selection in a comparitavely short term setting shouldn't apply in the naturally selected long-term. In cases of artificial selection where we are selecting for fat pigs, or against rattlesnakes with rattles, we are selecting for what is apparently the best for our own ends, not what is actually the best for the animals survival, or indeed, best for us.

I think one problem with the 'allele-frequency over time' definition is that a lot of people dont' seem to realise that this also includes frequencies of 1 and 0 and consequently allows for the generation of novel alleles and the extinction of alleles.This is connected to the frequent creationist claims that microevolution is only a pre-existing variant coming to predominate a population,the old more white or more black moth routine, and does not neccesitate any 'new' information.TTFN,WK

Yes.. that makes a lot of sense to me. I can see the distinction you are drawing between my pig-breeding and my rattlesnakes. Its seems eminently reasonable, especially the "is it going to survive better in the wild?" test...though now I come to think about it, don't you think that if we weren't around, that rattlesnake populations might be at an advantage if they did have rattles again? But you're totally right.Just to persevere with this a moment longer though, can you see any common ground between the intended and the unintended changes we've been looking at? I first started the original topic because I was thinking of human inginuity and its (often unintended) effects on life on earth.