Can Domestic Selection cause Macroevolution?

*Words emboldened by me.This thread occurred to me, while reading the Microevolution Vs Macroevolution thread, in which Faith equivocates the mechanisms of Domestic Selection (DS) and Natural Selection (NS) (See above quotes). She further goes on to say that it would seem that if Macroevolution did occur, then one would more likely observe it in DS than in NS; implying that this is proof against Macroevolution.Now, it could be argued that DS is a form of NS (albeit corrupted), in that humans act as the “natural” selecting agent. However, could one say that NS is just DS in nature?
I don’t think so. This goes back to me calling DS corrupted. I say this because that, which is selected for in DS, is what humans regard as desirable; this is not the same as naturally advantageous. For this reason, one would not often find a heavily domesticated animal, surviving, uncared for, in the wild. Maybe I’m out of touch but I still haven’t heard of packs of wild Chihuahuas roaming the Mexican desert . This is not to say that it doesn’t occur, but that it is a rare feat.It is clear, that the outcomes of DS and NS are often at odds with each other. Why is it then that one would expect to observe Macroevolution emerging from DS?
I would actually think it less likely.

Thread moved here from the Proposed New Topics forum.

NS is about the pressures excerted on a population by its enviroment .. and , in effect , these pressure will kill off the population unless the population is adapterd to the pressures ... over time these pressure may change and a small group with in the population may be better suited to survive the new presssures , and so will out breed the rest of the population and become the dominate variant .. until the pressure change again ..DS is about a derired outcome by a controling influence , it will pay no respect to the pressures from the enviroment , and will move the population to a new , posibly artifical enviroment to aid the selective process , DS will allow traits that LOWER the overall fittness for survial to become prevalent , accepting these as a cost of acheving the desired outcome ...the two are very different in how a individual is selected , how the population is shaped , and what factors direct the selective process .a good analogy is buying a car ..using NS ..you look at the service history , check tires , brakes , listen to the engine , try the lights .. then pickusing DS ..you ask is it blue ? does it have leather seats ? and does it have a 8-slot cd player ?both ways you get a car .... but very different carsThis message has been edited by ikabod, 04-04-2006 06:38 AM

I don't think that this distinction is meaningful. The "environment" that places NS pressures on a population includes all biotic and abiotic factors that it interacts with, and this certainly includes humans and human activities."Fitness" doesn't necessarily refer to the physiological robustness, but rather to reproductive success. From this perspective, an excellent "strategy" for increasing overall fitness is to enter into a symbiotic relationship with humans via agriculture. This type of selection is not even unique to humans; similar interactions occur with insects (ants, termites, ambrosia beetles) that practice fungus agriculture, for example.

I would agree with you here, however, to tie in with the OP, would you say that the oucomes expected of DS are the same as those expected of NS? Is it more likely for DS to show macroevolution than NS?

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"The good Christian should beware the mathematician and all those who make empty prophecies. The danger already exists that the mathematicians have made a covenant with the devil to darken the spirit and to confine man in the bonds of hell." - St. Augustine

The problem with artificial selection is that it has a tendency to reduce genetic variation to the extreme. For example, there was a horse in the 18th Century, called Eclipse. It is estimated that 80% of all thoroughbreeds have Eclipse in their pedigree. That seems indicative of a pretty small gene pool. I couldn't pretend to be an expert in animal husbandry, but my intuition tells me we wouldn't expect to see much in the way of large scale changes in that kind of lineage.With natural selection, the selective pressures are wide and varied, with a large amount of possible solutions, both morphologically and genetically. With a large population and fecundity it could be expected that over time many different attempts to solve the problem of reproduction in a dangerous world will be tried. Some will fail, others won't. This is where macroevolutionary changes are going to occur - when the selection pressure acts much more generally all the way down to the genetic level.Breeding doesn't do this so much. We can shape the animal (and as above, in a sense this is natural selection at work of a sort), but we select out far more aggressively than nature, and pick mates for the animal trying to steer evolution's course. This is more like taking a bush and chopping it so that it is very long and narrow. It might get taller, but it is not going to widen much.Dawkins invites us to imagine a multidimensional genespace full of every animal that could ever be. Normal evolution takes small steps through the gene space and if it ever reaches a point where an animals immediate neighbours are not very fit it is likely that the tendency would be to 'retrace' a couple of steps through the gene space and try another direction.With artificial selection we choose who mates with who and how often (sort of). This is kind of like taking slightly bigger steps through the gene space, without sending exploring fingers down other avenues (ie less genetic diversity). Is it any wonder that a breed might find themselves at a dead end quicker than a species might had it been able to wander down the paths of least resistance?It is possible that artificial selection based on the desires of men will arrive at a macroevolutionary solution, but given the restrictive nature of the selection process being used, I don't think it is particularly likely. It might be that in the background, the more sluggish natural selection might steer things generally towards a more macroevolutionary solution to keeping humans company/working with humans/feeding humans etc., and in some way that macroevolutionary change was influenced by artificial selection. Short term artificial selection is unlikely to arrive at such impressive solutions.

in replyYes human activites setup pressure on populations and effect the NS , BUT these are side effects of the human activity .. they are not seeking to drive selection , for example when we grow fields of wheat we do not do it to affect the NS pressues on field mice , we are not trying to DS field mice fitter to live in mono culture wheat fields , the same if we flood a valley to create a resovior , we do them for our reasons and the byproduct is a enviromental change on the local populations .. Just as if a natural landslide blocks a valley mouth and turns a river into a new lake .as to symbiotic relationships .. taking firstly the ant / fungus example the NS pressures are still there on the ants , and the fungus has swapped being vunerable to its own set of pressures and now is sharing the same pressures as the ants .with humans i would question if its a real symbiotic relationship , as humans can do without a particual breed / strain of plant , and will migrate to other areas to grow different crops , and in fact it is the humans who massivly decresse the size of the plants gene pool , a good example is apples , a centry ago there was hundreds of varities of english apples grown , now there is a handful , and they are only grown for commercial reasons , we dont need any apples , so if people buy pears and not apple we will stop growing apples , the reason for apple survival are pure DS not NS

It seems to me that there is an unresolved issue in Quantum Mechanics as to uncertainty(and causality) that could portend a shift in biology itself (say with the difference of hierarchic thermodynamics and macrothermodynamics) such that NS becomes DS even though historically DS gave rise to NS. It could be that the heterogenity of the environment (no matter the affect of the abiota biotically) becomes mastered by man technologically into a homogeneity that no difference of infinitesimal differences can materialize in macroscopic unobservables as they effect some or any difference of nature vs nurture in either case of DS or NS or the other way around.

I'll tell you what.CAn you show me a Chihuahua that can successfull breed with a great dane?Or a toy horse stallion that can mount a regular size mare???

Quantum mechanics is not a tool for anaylsing living system ... given enought time you could use quatum mechanics to describe every partical and bit of energy that goes to make up a cat but you cannot use quatum mechanics to describe the the hunting behaviour of the cat stalking a mouse or the enviromental pressure on the cat from a massive drop in mouse population due to ,say, disease .given that what you go on to say is equally non applicable .

I take it that you're saying that in these cases, even though, the great dane and chihuahua are the same species, taxonomically, that there is a "physical" reproductive barrier that could imply biological speciation. Am i right?The thing is, i actually have seen a case where a really small male dog, sired pups of a really big female dog. Don't ask me for refs, since it was a human interest story on the news many years ago. He basically "did his thing" while she was laying down
But that just goes to show that it is possible for these breeds to mate, however rare it might be, reinforcing the taxonomy.I'm not saying that macroevolution could never result from DS (i never say never, anymore), but it is not something one would expect to occur, unlike NS, where one might.It simply sets up a straw man to say that it would be more likely in DS than in NS.
Modulous gave a great account of the main reasons above.

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"The good Christian should beware the mathematician and all those who make empty prophecies. The danger already exists that the mathematicians have made a covenant with the devil to darken the spirit and to confine man in the bonds of hell." - St. Augustine

Can we equate macroevolution with speciation?If so and considering ring species as seperate species, couldn't we also consider a chihuahua and a great dane as seperate species and say that domestic breeding HAS lead to macroevolution. I type this becuase, it is my understanding that ring species are not genetically incompatible, they just do not interbreed because of their morphological differences, the same reason that a chihuahua and a great dane do not interbreed.So, can we say that DS has lead to macroevolution?I may be wrong, I'm asking.

I don't think it is clear that all ring species are only reproductively isolated pre-zygotically, i.e. genetically incompatible. There is some evidence that members of the Ensatina complex are tending towards post-zygotic isolation (Alexandrino, et al., 2005).If one does accept speciation as macroevolution and also accepts a behavioural or gross morphological basis for pre-mating reproductive isolation as sufficient to define a species then you would probably have a good basis for claiming that diversification of domestic dogs was an example of 'domestic' selection producing macroevolution.There are probably a lot of biologists who might be cautious of describing such a thing as an example of macroevolution. Ring species are more often suggested to be examples of incipient speciation rather than speciation, although they elegantly demonstrate some important mechanisms for speciation.TTFN,WK

I agree. Like I said, it depends...It depends on what you mean by macroevolution and where you draw the species line. But, in the context of convincing a YEC that DS has lead to macroevolution, or anything for that matter, I don't think this will work. I thought it was a good idea, i mean, you can look at it that way if you want too. It is just too hard to say exactly when the speciation has occured when looking at it within our extremely small time scale.

I would say that speciation is an initialization of Macroevolution.The question would then arise as to whether or not ring species constitute separate species, leading to "what is a species?".
If individuals are theoretically capable of breeding but don't, do they constitute separate species? An argument could be made that they represent variation within a species.If you see my reply to Ramoss, I have seen it happen that a really small dog and a really big dog (don't recall the breeds) were able to sire pups together.I would be willing to say that the possibility of later speciation does exist though, especially when taking WK's post into account.The crux of my question, however (though it may have been badly stated), was whether or not DS represents NS, to the extent that a lack of rapid macroevolution in DS could be used to support the position that macroevolution does not occur via NS?

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"The good Christian should beware the mathematician and all those who make empty prophecies. The danger already exists that the mathematicians have made a covenant with the devil to darken the spirit and to confine man in the bonds of hell." - St. Augustine