Talk:Evolution/Micro vs Macro

(Moved from Talk:Evolution --Brion 23:13 Jan 19, 2003 (UTC))

Micro/Macroevolution

I'm not quite sure why microevolution and macroevolution are in two separate categories. It's a distinction that deserves some attention, but evolution/natural selection should be first considered as a whole and the differences between the two explained in a small addendum. Macroevoultion = the appearance and dissapearance of species, microevolution = change within a species. Also, I feel the creationist/scientific debate deserves a place on this page, but it too should get its own category. One section for the current scientific theories, another for creationist objections, scientific rebuttals, creationist rebutalls to rebutalls etc.

-Emmett

Thats a misconception- although many scientists argue that the same processes are involved in the speciation and other 'macroevolutionary' phenomena there are others who think that different process are involved then microevolution. The evidence may be controversal, but I think that they should be treated as different subjects, especially as there is such a clear difference between the two schools of thought and a lot of evolutionary literature deals with this topic.

-Gog

Evolution has lots of interesting stories about scientists studying changes within existing species, such as antibiotic resistance in bacteria, but nowhere does it provide evidence that such changes can lead to new species, much less new forms of living things. --Ed Poor

This is one of the most oft-repeated myths around. There is abundant evidence of this. Even I (a non-biologist) can think of several new species that have been created by human breeding programs - the most obvious example is the nowhere-found-in-nature plant you are eating the crushed seeds of when you sit down for your morning corn flakes. It is worth noting that there is a very clever debating tactic used by anti-evolution campaigners here: first you claim that "science cannot identify any missing links between species" and then, once you have scientists running around pointing at examples of intermediate forms, you go limp on that charge and turn it around backwards, claiming instead that, seeing as there are all these intermediate forms, they are just variations around a mean, and therefore there is "no evidence for any new species". (I'm not suggesting that Ed said that, I should hasten to add, just that it's a common debating tactic amongst the more unscrupulous campaigners, and one that writers on evolution need to be aware of.) Tannin 06:47 Jan 9, 2003 (UTC)

Another reasonably clear example can be found with the liger and tigons. Although the lion and the tiger can be considered to be of the same species (felid), they in fact have not been bred very successfully- the cross ends up with immune system difficulties; and the males are sterile (and nearly all female tigons are sterile). Clearly, the genetic drift between the two species has reached the point where they can be interbred only with extreme difficulty. This can be expected to only get worse with time, unless some environmental force pushes them back together, breeding from the rare fertile females. There's a speciation event happening right there.[[:|]]

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The field of evolution is divided into two broad areas; microevolution and macroevolution.

Do actual biologists make this distinction? I know creationists do, in which case we should discuss it in that context (and possibly in the article on creationism or intelligent design). --Robert Merkel

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No, biologists don't use those terms; they are the inventions of creationists so their definitions can change to dance around whatever evidence turns up. --LDC

I raised the same objection to Maveric149, and he convinced me that it is indeed a biological concept. I did some more checking on my own and indeed, these are valid biological terms. The point of contention is whether there is an absolute or relative difference between micro- and macroevolution. Scientists use ther terms to gloss a relative distinction. Creationists use the terms to argue for an absolute distinction. But to claim that micro- and macroevolution are two distinct processes is wrong and misconstrues scientific usage of the terms. Slrubenstein

I just did a major revision of the format and I think the article makes a lot more sense now. However, it is still confusing, largely because there is too much chatter, especially in the macroevolution section. I wrote an introduction for that section (which should really be the entire section) and I hope it clarifies the essence of the macroevolution debate among scientists. Regarding creationists and macroevoltion: if the macroevolutionists are right, then there is a huge issue in the history of life with little or no explanation. Most scientists don't have a problem with this; it just means that there is more work to be done. Any time a scientist says "I don't know", some arrogant fool has to jump in and pretend that he has all of the answers. adam

First, I have a question. Can we have "macroevolution" (as a concept) without "macromutation". I don't want to hear "Yes, we can have speciation without a special class of mutations specifically for that purpose." I want to know if anyone speaks of macroevolution without the assumption that it is caused by a specific type of mutation. Without "macromutation", I don't see how "macroevolution" is any different than speciation and divergence. However, I did a Google search for "macroevolution" and found a few articles that defined macroevolution without reference to macromutation. If they are separate concepts, I made a mistake; my knowledge is limited to the debate over macroMUTATION and I know nothing about macroevolution.

That being said, I tried to report the current status of the macromutation debate among scientists. Some scientists have told me their opinion first hand (and even if they don't believe in macromutation, their explanation of their belief showed that they are aware of it as a debate among scientists). Similar information can be found by doing a Google search on "macroevolution". I haven't done a search on "macromutation" yet. Anyway, I wrote this and some anonymous person trashed what I wrote and attributed my opinion (and the opionion of my professor) to creationists. LEAVE THE CREATIONISTS OUT OF THIS!!! I wish this person had read the talk page, and had read the articles referenced by Google, and had signed in so that I could direclty communicate with him.

BTW: This page should be limited to the general scientific consensus about evolution. Macromutation is an ongoing debate and should only be mentioned. Likewise, macroevoltuion (if there is such a thing independent of theories of marcomutation) is a very specific field and should also only be mentioned. This is very frustrating adam

If I may anwser my own question; I have just started reading Gould's "Structure of Evolutionary Theory" and he repeatedly uses the terms "macroevolution" and "microevolution". To avoid argument, he wants to use them in a purely descriptive way, leaving an open question about whether they are different processes. Using this descriptive definition, the main reason for the distinction is that we learn about macroevolution and microevolution through different methods...basically macroevolution is what a paleotologist sees, while microevolution is what a geneticist sees. adam

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Viruses and Macroevolution: Evolution almost certainly occurs in many different ways. We are well aware of mules of different species: animals that are offspring of two different species, which are themselves sterile. Their existence shows that relatively minor genetic changes can sterilize a creature. This begs the question, "How does the number of chromosomes change and result in a new species?" The probability of identical mutations is astronomically small, unless it is catalyzed in some way. My favorite candidate for such a catalyst is viral infection. One could imagine a virus that infects a population of females, causing identical mutations to their egg cells, or to their feti' egg cells. Thus, it may well be that higher life forms are symbiotic with viruses, and we would not be here except for viruses! Rudminjd 15:41 20 Jul 2003 (UTC) Joseph D. Rudmin

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For those who think that "macroevolution" is not a term used by biologists, go to http://www.pubmed.com and search for these terms in publications. Macroevolution gets 73 hits, microevolution gets 175. I've also seen "macroevolution" used in a grant proposal to describe the evolution of a particular genus. I think it is safe to say that any evolution researcher is familiar with these terms and many/most would be comfortable using it in purely descriptive terms. With that in mind, I am going to remove a blatantly false statement from the article. adam

There's hundreds of thousands of articles on pubmed (with >140000 using the word evolution alone), so I'd argue instead that the usage of these terms is very rare. (~ .05%) Kim Bruning 09:59, 24 Apr 2004 (UTC)

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Also, the introduction is too heavy on population genetics. Laymen (our target audience) don't think of species as being a difference in gene frequenceis, and neither do most biologists. Laymen probably can't understand that comment about gene frequencies. Also, I think it is rather cocky for someone to declare that they understand the general genetic basis for species differences when we have just started to investigate the specific genetic differences between species. adam

Another Question: Should the comparison be made between "biologists" and "creationists"? Cant a Biologist believe in either theory abput our origin... or somewhere in between?

Yes, biologists are free to believe that they want. On the other hand, given the centrality of evolution to biology, it's difficult to work as a scientist in the field of biology if you reject evolution. For example, any extrapolation from one species to another is only valid if you assume relatedness (and thus, common origins, "descent with modification", all that stuff). Without evolution, the idea of "rodents" is nothing but a grouping of convenience, and you cannot assume that knowledge about one species gives you any insight into another. Without subscribing to evolution anyone who does "animal testing" is engaging in nothing other than cruelty to animals, since there is no logical reason why monkeys should react to drugs in a more human-like manner than slugs would.

Biology without evolution requires the assumption that God created a world which is identical to one that evolved. In which case, you need to function as if you believe in evolution. Biologists might claim not to believe in evolution, but they still function as if they do. I am unaware of any biologists who are creationists and do logically valid research that works from that assumption. Guettarda 20:30, 9 Dec 2004 (UTC)

"any extrapolation from one species to another is only valid if you assume relatedness" - that's false. Extrapolations, analogies and taxonomic grouping is based on the similar or common structures the species have. It existed before the theory of evolution. Relatedness is only an evolutionary explanation for the existence of the common structures. If one wishes do believe in something else than evolution, he or she may want to explain the similarity in other ways, for example modular design (or have no explanation at all - like the atheists and agnostics had before darwin)

Metaphysical theistic creationism and the scientific theory of evolution are not mutually exclusive, metaphysical materialistic evolutionism (this is not a scientific theory, it's a philosophy) and creationism are.

"you need to function as if" - actually, it's the other way. Evolutionists function as if there was design, they even use as-if-design terminology. Nothing progressive in science is based on the theory of evolution. The only thing I know about is former mistreatement in medicine because of belief in vestigial organs. The whole science could succesfully go without it.--charon 16:25, 11 Jan 2005 (UTC)

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Mutations to existing species resulting in entirely new species have been observed in the field.

because it's a big claim with no support given. The claim is somewhat controversial, in that I think creationists dispute this. Assuming the claim is true, I hope that someone will re-add the statement to the article with a couple of examples of observations of the creation of new species by random mutation. Above on this talk page the example of corn is mentioned, corn being modified by human agriculture, I think. I'm not sure if biologists would agree that this is a species change; in general, examples given should clearly state why the example meets the criteria for a new species. Zashaw 22:46, 3 Feb 2005 (UTC)

Allopolyploidy in plants, for one. Hybridisation followed by chromosomal doubling. That's a pretty solid, and basically instantaneous speciation event. And gives lots of fodder for evolution, since you have a whole extra genome to experiment with; you can mutate key enzymes and not have to pay the consequence of loss of functionality. The origins of corn are disputed, but most most probably corn originated with either a hybridisation even like the one described, or with "catastrophic re-organisation" of the genome. Only after corn speciated was it subject to selection by humans.

Wheat had two such events; the new species were most probably encouraged and propagated by people, but the hybridisation and doubling was natural. Einkorn wheat hybridised with one species of goat grass. The sterile hybrid became fertile through the production of unreduced gametes (meiosos failed to occur properly). Not that rare an event. Product - fertile emmer wheat, basic crop of the Neolithic revolution, origin or agriculture, etc. Emmer wheat hybridises in the same way with another goat grass. Bread wheat comes about. In cultivation, yes, but it was a spontaneous process, between a crop and a wild plant.

Results cannot breed with parent species, very different. Polyploidy is the easy answer - it's the only one that happens fast enough to see. But it happens, gives rise to new species, disproves the "like only gives rise to like" idea. Guettarda 00:22, 4 Feb 2005 (UTC)

I read the above sentence in the article and had a real problem with it as it stands, too. I think it needs some form of backup/reference, or at least a simple example, otherwise it just looks like an unsupported claim. Anyone who understands the issue care to condense one of Guettarda's examples down for the article? maebmij 04:10, 3 Jun 2005 (UTC)

What would be an adequate reference? I have had the argument with creationists before, and it seems that whenever you give an example of speciation is countered with "shifted goalposts". Triticale is an example of a totally new species that was generated through this process - of course it's an artificial hybrid, but it uses the process that was inferred from wheat evolution. The simple fact of the matter is that speciation is an almost trivial process - there are disjunction bird populations which should be considred different species because they do not recognise each other's songs, and so would not interbreed under natural conditions. That is sufficient for speciation. Trivial, but it now allows the two groups to wander in different directions (either through drift or selection). Once you have speciation microevolution turns into macroevolution - changes between species rather than changes within species. Another example (if memory serves me) is a new polyploid Spartina which originated and spread in Europe in the mid-20th century. I suppose the wheat example is the best one, but there is a nice example in the Triangle of U article. Guettarda 04:41, 3 Jun 2005 (UTC)