Can Domestic Selection cause Macroevolution?

Hi folks, new poster here although I've been lurking for a while.If we limit this topic to animals I don't think we can reasonably expect to see speciation within the 15,000 or so years which have passed since we started domesticating animals. The art and eventual science of animal husbandry which allows us to breed for or against specific traits has been around for considerably less time.Most domestic animals have a life expectancy of from 10-20 years (considerably less for animals bred specifically for meat which is a much more recent practice than other uses). And we have long recognized the advantages of bringing in new blood to strengthen stock lines(including the addition of wild members of the species). Both factors which should reduce expectations of seeing speciation within domestic animals.I believe the case has been made that we have seen speciation within domesticated plants. I just wonder if that's sufficient for the critics.On a side note to Faith who thinks meanings change too fast, I'd like to remind you that we're communicating in a living language that grows and changes as we do. We can't expect words to hold the same meaning forever unless we want to invent words as fast as we change. How much good would it do me to tell you that while macroevolution has never been observed, grizification has?As a party to this conversation you are just as responsible as the writer for understanding the meaning and context of the writer. Since this is a science forum you should also realize that the scientific definition for any particular word is usually more appropriate than the common definition.If I look up the word in a dictionary I can immediately see that the word can be used in many ways:

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spe·cies ( P ) Pronunciation Key (spshz, -sz)
n. pl. species
1.Biology.
A fundamental category of taxonomic classification, ranking below a genus or subgenus and consisting of related organisms capable of interbreeding. See table at taxonomy.
An organism belonging to such a category, represented in binomial nomenclature by an uncapitalized Latin adjective or noun following a capitalized genus name, as in Ananas comosus, the pineapple, and Equus caballus, the horse.
2.Logic. A class of individuals or objects grouped by virtue of their common attributes and assigned a common name; a division subordinate to a genus.
3.
A kind, variety, or type: “No species of performing artist is as self-critical as a dancer” (Susan Sontag).
The human race; humankind.
4.Roman Catholic Church.
The outward appearance or form of the Eucharistic elements that is retained after their consecration.
Either of the consecrated elements of the Eucharist.
5.Obsolete.
An outward form or appearance.
Specie.

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[Middle English, logical classification, from Latin specis, a seeing, kind, form. See spek- in Indo-European Roots.]

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If I look a little harder (okay it's really on the same page) I can find medical dictionaries to help me understand how a scientist might use the word:

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spe·cies (spshz, -sz)
n. pl. species

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A fundamental category of taxonomic classification, ranking below a genus or subgenus and consisting of related organisms capable of interbreeding.
An organism belonging to such a category, represented in binomial nomenclature by an uncapitalized Latin adjective or noun following a capitalized genus name, as in the bacterium Escherichia coli.
A class of pharmaceutical preparations consisting of a mixture of dried plants in sufficiently fine division to be used in making boiled extracts or infusions.
A specific type of atomic nucleus, atom, ion, or molecule.

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Source: The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

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Main Entry: spe·cies
Pronunciation: 'spE-(")shEz, -(")sEz
Function: noun
Inflected Form: plural species
1 a : a category of biological classification ranking immediately below the genus or subgenus, comprising related organisms or populations potentially capable of interbreeding, and being designated by a binomial that consists of the name of the genus followed by a Latin or latinized uncapitalized noun or adjective agreeing grammatically with the genus name b : an individual or kind belonging to a biological species
2 : a particular kind of atomic nucleus, atom, molecule, or ion

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Source: Merriam-Webster's Medical Dictionary, © 2002 Merriam-Webster, Inc.

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Source: Species Definition & Meaning | Dictionary.comJust as long as the writer used the word with a meaning similar to one of the above definitions (and not a definition from say the 1930 edition), a reasonable reader can be expected to understand exactly what the writer means. Playing word games looks like an attempt to dodge the underlying issue.

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When science and the Bible differ, science has obviously misinterpreted its data.
- Henry Morris, Head of Institute for Creation Research

i would reply that they did not pick this path, and without our intervention the version of corn we eat would have died (never mind never having been created). There's nothing symbiotic about this relationship. Unless you want to call mankind a bunch of parasites.when did I assume that we would suddenly disappear? What if we were to just stop eating corn?

This is nonsensical. What does "picking a path" have to do with the discussion? Everything dies, the issue in this case is reproduction. Domesticated maize now requires us for part of its life cycle, just like in any other obligate symbiosis (from mutualism to parasitism). One way of looking at it is that domesticated maize is well-adapted to exploit humans as a highly efficient dispersal agent. As I have pointed out, it has proven to be a very effective strategy for this lineage.This is not at all unusual. Flowering plants have developed structures allowing them to exploit insects and other animals for pollination, and specialized fruit to employ animal seed dispersers. Their animal counterparts have also adapted to better benefit from the relationship. This is coevolution in a nutshell. I have demonstrated that both humans and maize, as species, benefit from their interaction in the same way that other well-documented symbiotic organisms do in nature (such as ambrosia beetles and their fungi). If you think you can refute this, please do so. Your comment about parasitism is a non sequitur, as far as I can tell. Well, disappear from the interaction, anyway - same issue and same problems with your statement.This message has been edited by Belfry, 04-05-2006 08:41 PM

Symbiosis is not the same as parasitism. Symbiosis is defined as a relationship between two dissimilar species that is both intimate and potentially obligatory. Largely, the contiuum of symbiotic relationships can be described as:1) Mutualism, where the two organisms each benefit from the relationship;
2) Commensuralism, where one organism benefits and another is not affected;
3) Parasitism, where one organism benefits to the detriment of another.The relationship between humans and our crops could certainly be described as mutualism, and therefore does qualify as a symbiotic relationship. Humans benefit from the food source provided by corn; Zea mays mays certainly benefits from human husbandry to the extent that it has become the world's most popular and profitable cereal crop.This message has been edited by crashfrog, 04-05-2006 09:09 PM

when I said died, I should have said become extinct. As far as I know, in no symbiotic relationship (in which there are those three types: commensualism, parasitism, and mutualism) does one alter the other for its own purpose.and if you remember, in first post on this topic I said I may have been shooting myself in the foot.evolution, as I understand it, has no pre-picked paths. It is not goal-oriented. Birds did not develop wings in order to fly, but fly becasue they have wings. We did not develop a brain in order to think, but rather think becasue we have a brain. I might need to clarify this at a later point.The corn, as for that matter all domesticated crops and animals, have been selected for with specific goals in mind. With corn, it was to produce a plant that would provide us with a better food source. Why do you think we introduced Russian wheat to the US? Russian wheat is better at surviving winters, and it would not surprise me that we have been hybridizing for that trait with our own wheat.

really? you contradict yourself later on another contradiction if mutualism is one type of symbiotic relationship, which the defintion you provide earlier does say, then how can you claim that mutualism is not symbiotic, or parasitism for that matter?

hey, this is this dudes brother. while i can see where you're coming from i think, which is that they are three completly different definitions but the only problem there is if you take two of the three that fall under symbitotic relationship there is only one left and though the english language is messed up why would they make two completly different words for the same thing and the other two you discluded fall under symbiotic relationship due to both of these definitions which makes your argument completly pointless along with the fact that you cannot even argue a simple arguement even a little bit on the good side. and although these is one extremly one long run on sentence it still makes more sense then your pitifull excuse for an argument.

Just a point of correction: a number of parasites induce behavioral or other changes in their hosts - especially intermediate hosts. One example:Robb T, Reid ML, 1996 “Parasite-induced changes in the behaviour of cestode-infected beetles: Adaptation or simple pathology?”, Canadian Journal of Zoology/Revue Canadien de Zoologie. Vol. 74, no. 7, pp. 1268-1274.

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Abstract:

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Although the cause is often unclear, many parasites alter the behaviour of their intermediate hosts. The larval form of the rat tapeworm, Hymenolepis diminuta, has previously been shown to modify the behaviour of its intermediate host, the flour beetle, Tribolium confusum, in a manner that may be adaptive to the parasite. To test this explanation we observed host behaviours including activity, concealment, and the response to and production of pheromones. Infected female beetles examined both 4-5 and 11-12 days post infection were slower moving and slower to conceal themselves than uninfected conspecifics; however, they did not differ from uninfected individuals in staying concealed. Infection of T. confusum did not affect the production of pheromones by mated and virgin females or the response of females to male pheromones. A second hypothesis for altered behaviours may be that modified behaviours result from pathology. The survivorship of mated infected female beetles was significantly lower than that of infected virgin beetles and uninfected beetles. Thus, both mated status and infection were important factors in survivorship, but only infection had significant effects on the altered behaviours. In this system, therefore, the hypothesis that behavioural changes are due to adaptive manipulation of the host by the parasite is supported.

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I think this is a pretty clear indicator that at least sometimes parasites DO alter their hosts for their own benefit.

Conscious intent is immaterial, though it may make the process more efficient. The process in non-human examples is much the same as in human agriculture; crops which are more beneficial to the cultivator (be it human or insect) are selected for, deleterious phenotypes are selected against. Not until we developed more direct genetic manipulation techniques (gene insertion and such) did human methods fundamentally differ from this process. This is essentially correct... it's not necessarily goal-oriented, but even if evolution is guided by humans, with humans as the primary NS agent and with a human goal in mind, it's still evolution. Well, I think it is arguable whether the Native Americans foresaw what would result when they started to cultivate that native annual grass, or whether they just preferentially cultivated varieties that arose on their own.In any case, I agree that human consciousness and forethought are unique in contributing to these interactions. However, "domestic selection" still isn't a fundamentally a different process from natural selection. The more beneficial plants are still selected as more "fit," it's just that human perception is the primary determinant of fitness in that case.

Everyone, please ignore the post my brother made. He's a bit rude, if you couldn't tell, and while he can think, its a touch difficult to understand him a times. And I need to remember to log off when I'm finished.As far as I can tell, I'm defending the OP, in that NS and DS are two different processes. I wasn't aware of the parasites changing the behavior of the hosts, but does this have an affect on that host's evolution? The answer is most likely yes, but I should probably read that paper in full before I open my mouth.I'm not sure how one can equate a human as being the agent of NS in the domestication of animals and plants.In ToE, fitness is measured by the number of offspring one has and some other factors dealing with those offspring (if I'm not mistaken). If one has more offspring, the more your genes are present, and if they are beneficial, they will eventually become the dominant phenotype. That is the fitness of NS.The fitness we look for in crops and animals is not their ability to produce successful offspring, but their ability to provide us with a better yield. This fitness is not the same as that in NS, and therefore DS becomes a corrupted version.

We welcome his participation, but he needs to do as other brothers here do and get his own login.

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agreed.

Whoa! Didn't expect this topic to blow up overnight.Welcome Faith Glad you could join us. Nothing like a bit of YEC interjection to get the pulses racing on this forum... That's just it tho, Faith. DS is a lot more intense than NS. It is this increase in intensity that would possibly limit its macroevolutionary potential. For macroevolution to occur (and i am using a speciational definition*, will get to this just now), variation (old and new) is required. DS often results in a much faster decrease in variation than NS; so much so that it could restrict the function of variation in speciation.Apart from the above, DS is strongly directed. Humans breed for the characteristics they want. This, added to the weakened effect of variation and drift, could also, intuitively, restrict macroevolution; since humans aren't breeding FOR macroevolution.Then,to bring in a point that Ned raised, macroevolution is not only about Selection. There are other factors involved. Some that, maybe, would lend to DS causing speciation, and some that would take away from this possibility.it should be noted, I'm not saying that speciation is impossible under DS; just that it is, intuitively, less likely.*Speciation in the sense that two different species are genetically incompatible. I do this since there is no reason to set macroevolution at a higher taxonomic level, which are usually just arbitrary anyway.
Fact is, i've noticed that it is often the case that anti-evolutionists get to "set the limits", and evolutionists usually just accomodate them. I don't see why this should be the case, and i tire of it. (Any reply to this particular statement should be taken to the
Microevolution vs Macroevolution thread.

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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

I found a few studies in plants addressing some of the issues brought up here. For example So genetic gain in the selected (bottleneck populations) can lead to rapid diversification i.e. potential macroevolution...but the trait being selected is fairly broad as opposed to most DS scenarios..this makes this study a bit more realistic in terms of NS.A similar study in butterflies Also, corn after domestication changed in macroevolutionary terms but also regained genetic diversity quickly even though coalescence suggests a founder population of only 20 individuals And from mammals, it shows depending on how one selects, the populations can separate (macroevolution) or merge

Always great to have you around with references! Makes the rest of us have to scramble to get them and catch up