Microevolution, does it equal Macroevolution?

[FreeThinker]

For a long time I was convinced that microevolution (e.g. the evolution of different breeds of dogs, the Galapagos finches an so on…) over millions of years would lead to Macroevolution (appearance of new species). However, I now question this. Microevolution is the selection of particular alleles under the pressure of natural selection. Macroevolution is completley different. It is by the appearance of new genes, new characteristics and is therefore driven solely by mutations ( Allready known and accepted by the scientific community). My reasoning is quiet simple, no matter how much you shuffle the existing genes around; they will still be compatible with each other. This would explain why we get such large phenotypic differences in the breeds of dogs, yet any two breeds can still produce fertile offspring between them. Basically, without mutations there can be no speciation, and ultimately, macroevolution is not just microevolution over long periods of time. I am assuming a couple of things here; 1) the breeds of dogs (which are the most common example of microevolution) derived from the wolf are the result of selection of alleles and not mutations 2) same goes for the Galapagos finches. I don’t doubt that macroevolution happens, I just dont think that it is microevolution in the long run. Discuss.

 

Btw, this is not some creationist attack on evolution, infact I am studing to become an evolutionary biologists. This is just something thats been in my head for the last couple of days and I feel it will make an interasting discussion.

[jeskill]

I thought that the driving forces of microevolution (ie. the processes that drive the change in allele frequencies) are selection, genetic drift, migration and mutations.

[Mokele]

But mutation is part of microevolution too. New genes arise and spread through populations.

 

Consider the populations on two islands, which start out the same. Both will evolve to suit their environment, which involves mutations as well as just changes in frequency. Eventually, enough differences accumulate that the two no longer could or would interbreed if re-introduced.

 

The important thing that I think you've missed is that mutation and new genes are not strictly macroevolutionary, and occur within populations during microevolution as well.

 

It's also important to remember that all individuals have a resevoir of genetic diversity. On average, individual vertebrates are heterozygous at 5% of their genome, far too many genes for selection to effectively act on (plus most are neutral and constantly being mixed within the populations).

 

Mokele

[FreeThinker]

But mutation is part of microevolution too. New genes arise and spread through populations.

 

In that case, everything would make sence. I just need some evidence. Have any mutations been located in the genome of any breed of dog? If yes, could anyone provide a link to the paper/article?

[Mokele]

Have any mutations been located in the genome of any breed of dog?

 

There are numerous breed-specific genetic diseases caused by mutations and the deleterious effects of inbreeding. Two papers are:

http://www.genome.org/cgi/reprint/10/9/1271.pdf

http://hmg.oxfordjournals.org/cgi/content/abstract/11/2/165

 

Both use the dog genome to identify mutations of interest.

 

However, I also think you're drastically underestimating the rate at which germline mutations occur. On average, a newborn human contains 5 mutations that affect final protien structure.

 

Here's a paper on the overall mutation rate in mammals, which is apparently a constant rate per year per base (accounting for the higher rates of some species). As you can see from the number (multiplied by the number of bases in a genome), mutations are very, very common. Even gene duplication events are more common than we think.

http://www.pnas.org/cgi/content/full/99/2/803

 

Mokele

[FreeThinker]

Thanks for the links Mokele.

[lucaspa]

For a long time I was convinced that microevolution (e.g. the evolution of different breeds of dogs, the Galapagos finches an so on…) over millions of years would lead to Macroevolution (appearance of new species). However, I now question this. Microevolution is the selection of particular alleles under the pressure of natural selection. Macroevolution is completley different. It is by the appearance of new genes, new characteristics and is therefore driven solely by mutations ( Allready known and accepted by the scientific community).

 

Microevolution also works on new alleles -- mutations. An allele that has been in the population for generations is not the only type of allele that can undergo positive selection, is it? If a new mutation is advantageous, then natural selection (which you seem to be equating with microevolution) will also select the new allele.

 

But macroevolution can also be the result of shuffling of alleles, too. Most traits we can see are the sum of many genes. And different alleles of those genes will give different traits. If we are looking at say the shape of teeth, that is under the control of many genes. One set of alleles would give teeth better suited to eating plants and another better suited to eating meat. In an omnivore population in an evironment where plants are scarce but prey plentiful, an individual with teeth better suited to eating meat would have an advantage. So, those alleles contributing to those type of teeth would be kept and alleles for teeth for plant eating would be lost. Over many generations, the alleles for teeth for eating plants would disappear entirely from the population and only those alleles for teeth for meat eating remain.

 

My reasoning is quiet simple, no matter how much you shuffle the existing genes around; they will still be compatible with each other.

 

Not necessarily.

 

This would explain why we get such large phenotypic differences in the breeds of dogs, yet any two breeds can still produce fertile offspring between them.

 

That's not entirely true anymore.

 

Basically, without mutations there can be no speciation, and ultimately, macroevolution is not just microevolution over long periods of time.

 

Nope, you could have speciation without any mutations. Simply separate the allele populations.

 

However, you are getting close to a truth: macroevolution also involves reproductive isolation. However, since reproductive compatibility is also a multigenic trait, if you separate the allele packages entirely, then eventually you lose the ability to interbreed and produce fertile offspring.

 

But I need to caution you here, the biological speciation concept only requires that populations DO NOT interbreed. Genetic incompatibility is only the most dramatic example of reproductive isolation. However, if because of behavior, differences in the size or shape of reproductive organs, cues as to mate selection, etc are operative, then you have 2 separate species even if, were you to use artificial insemination, you could produce fertile F1 hybrids. The fact on the ground would be that there are no F1 hybrids.

 

"But we must ask, what exactly are these genera, families, orders, and so on? It was clear to Darwin, and it should be obvious to all today, that they are simply ever larger categories used to give names to ever larger clusters of related species. That's all these clusters, these higher taxa, really are: simply clusters of related species.

 

Thus, in priniciple the evolution of a family should be no different in its basic nature, and should involve no different processes, from the evolution of a genus, since a family is nothing more than a collection of related genera. And genera are just collections of related species. The triumph of evolutionary biology in the 1930s and 1940s was the conclusion that the same principles of adaptive divergence just described -- primarily the processes of mutation and natural selection -- going on within species, accumulate to produce the differences we see between closely related species -- i.e., within genera. Q.E.D.: If adaptive modification within species explains the evolutionary differences between species within a genus, logically it must explain all the evolutionary change we see between families, orders, classes, phyla, and the kingdoms of life. Niles Eldredge, The Triumph of Evolution and the Failure of Creationism. pgs 76-77. [emphases in original]

[FreeThinker]

lucaspa,

 

If we have an individual who is homozygous for a particular allele and another one who is homozygous for the other allele, they can still interbreed. Let assume the same two individuals also are also homozygous for a different allele in another loci. Can these two individuals still interbreed? Yes. Are they difference species? No. My point is simple, just because we have allele selection, it does not mean that we will get a new species emerging. Of course that depends on the definition of specie. For my purpose, specie is formed when it cannot breed with its most recent ancestor. I don’t doubt that shuffling of alleles happens. In fact, I don’t doubt macroevolution happens either. My original post was referring to the mechanisms of both, and whether they are the same. Mokele provided me with some papers indicating the rate of mutations in dogs/mammals. I don’t think we can draw a line between micro evolution and macroevolution, just as we can not draw a line between day and night. The two are obviously different but we cannot definitely point out the time when night turns into day. It is a gradual process which happens without being noticed. Microevolution starts with allele shuffling. A geographic boundary might split the population. This could be labeled as a milestone in the formation of new species. However, gene shuffling would still be going on for some time, and no new species is formed. If an individual from one side managed to cross to the other side, he could still interbreed with the other population. As mutations add up, the species become different. The real question is, how much does the genome have to change in order for the two populations to be different species (not be able to produce fertile offspring). Obviously one mutation wouldn’t equal speciation. Would two, three, four, a hundered? This is equivalent to the day and night metaphor. There is no sharp line, but day and night still remain different. In conclusion, if we look at microevolution as just the shuffling of alleles, it doesn’t equal macroevolution. My original argument was that all dog breeds were just the result of gene shuffling and that no beneficial mutation of a gene has been documented. If this is our definition of microevolution, it is not the same as macroevolution. If we introduce mutations, and we would have to look at the genomes to find them, than the two become the same thing.

 

Edit: When I think about it a bit more, maybe I am wrong. What is the genome of two species other than different alleles? We can transfer a gene from a fly into the mouse and have it function as normal... There is no "different" genes, just "different combinations of genes". Hmmm... now that I think about it, I am wrong.

[Mokele]

If we have an individual who is homozygous for a particular allele and another one who is homozygous for the other allele, they can still interbreed.

 

Not necessarily. What if that locus is the protien that governs sperm recognition by the egg? Now the two alleles are incompatable.

 

The changes that genetically isolate two populations can be major (big morphological or habitat changes), but can also be minor (doing the wrong courtship dance, having the wrong colors to be identified as a potential mate, having a larval stage that requires the metabolic product one one host but not another).

 

Of course, there's also the factor of when and where during life genes turn on and off. We're 98% identical to a chimp not because we're that close morphologically (clearly not), but because we build our bodies with the same developmental toolbox, and just change when and where certain tools are used. (Think of it like a house; most houses are made with the same materials and tools, but it's how the tools are used, how the materials are manipulated, and how they're put together that matter.)

 

Of course, the reproductive isolation definition isn't perferct either; I've seen living offspring of cross-*genus* hybrids (though I doubt it was fertile). Plenty of hybrids are either self fertile or fertile with a parent species.

 

So basically, it's a big, ugly mess without any nice clean rules that can be applied, and attempts to make nice clean rules will inevitably be foiled by the sheer messiness of nature.

 

Mokele

[lucaspa]

lucaspa,

 

If we have an individual who is homozygous for a particular allele and another one who is homozygous for the other allele, they can still interbreed. Let assume the same two individuals also are also homozygous for a different allele in another loci. Can these two individuals still interbreed? Yes.

 

To back Mokele, not necessarily. Especially when we start going to 5 or 10 loci (which is pretty common for polygenic traits). Are they difference species? No.

 

My point is simple, just because we have allele selection, it does not mean that we will get a new species emerging.

 

Eventually, yes we will. Remember, what happens is that some alleles disappear from a population while new alleles become fixed. So, if we have 2 populations side by side, one undergoing selection for different alleles (population A), and the other not (population B), over generations Population A is going to have a completely different set of alleles than B.

 

Of course that depends on the definition of specie. For my purpose, specie is formed when it cannot breed with its most recent ancestor.

 

That's not the biological definition. The biological definition is that we have a different species when the populations do not interbreed, even when in close contact. Whether they can or not becomes irrelevant. The gene pools are separate when they don't interbreed even if they have the chance.

 

I don’t think we can draw a line between micro evolution and macroevolution, just as we can not draw a line between day and night. The two are obviously different but we cannot definitely point out the time when night turns into day.

 

The two are NOT "obviously differnt" Instead, the quote from Eldredge I gave says the processes of microevolution lead to macroevolution.

 

If selection for a new environment happens to all of all of the original population, we end up with transformiing the entire population into a new species. This is difficult to test with interbreeding because we don't have a time machine to go back and retrieve members of the population 5,000 generations ago to see if they can interbreed with the members of the current population. So we test out sympatric and allopatric speciation -- comparing two populations separated by either geographical or ecological barriers.

 

It is a gradual process which happens without being noticed. Microevolution starts with allele shuffling. A geographic boundary might split the population. This could be labeled as a milestone in the formation of new species. However, gene shuffling would still be going on for some time, and no new species is formed. If an individual from one side managed to cross to the other side, he could still interbreed with the other population. As mutations add up, the species become different. The real question is, how much does the genome have to change in order for the two populations to be different species (not be able to produce fertile offspring).

 

Let me go in reverse order. There are genes that control hybrid sterility. This paper discusses changes to those genes -- different alleles -- that result in hybrid insterility: M Nei and J Zhang, Evolution: molecular origin of species. Science 282: 1428-1429, Nov. 20, 1998. Primary article is: CT Ting, SC Tsaur, ML We, and CE Wu, A rapidly evolving homeobox at the site of a hybrid sterility gene. Science 282: 1501-1504, Nov. 20, 1998.

 

Your local library will have that article. If you have trouble, let me know and I can either attach the PDF file or cut and paste the relevant data.

 

Allopatric speciation is well documented both in the wild and the lab. Instead of "gene shuffling", what you want is "gene flow" between the isolated population and the main population (A and B, respectively). And yes, speciation is a balance between isolation and gene flow. Where a population has a large range with different habitats, there is what is called "disruptive selection". This is where the sub-populations are being selected for different environments but gene flow is retarding the fixation of alleles. Humans today are undergoing disruptive selection.

 

There is also sympatric speciation where population A and B are in the same geographic area but now isolated by a different ecological niche. Apple maggot flies is one example. Another recently documented example are 2 populations of salmon -- but one breeds in the shallows of the stream and the other breeds in the deeper center. Now they don't interbreed at all.

 

Now what you are missing, I think, in your "gene shuffling" is that selection works such that a particular allele will become "fixed" in the population. That is, EVERYONE will have that that allele and no other allele. Also alleles will be dropped from the population so that NO ONE will have that allele. Thus, over the course of generations, some alleles can't be "shuffled" because they either aren't there anymore or there are no competitor alleles. If the environment for the peppered moths had continued with dark trees, the alleles for light colored moths would have disappeared from the population.

 

So, natural selection working at what you call the microevolution level can create a population that has completely different alleles from the original.

 

Obviously one mutation wouldn’t equal speciation.

 

It could. IF it occurred in a Hox gene. These are high level developmental genes that control major body changes. For instance, a change in just ONE base converts a multilegged animal like a millipede into a 6 legged animal like an insect: 1a. http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/vaop/ncurrent/full/nature716_fs.html Hox protein mutation and macroevolution of the insect body plan. Ronshaugen M, McGinnis N, McGinnis W. Nature 2002 Feb 21;415(6874):914-7

 

Would two, three, four, a hundered? This is equivalent to the day and night metaphor. There is no sharp line, but day and night still remain different.

 

Right, and the number of differnt alleles changes from situation to situation. Sometimes it might take 1,000 new alleles, in another case only 1.

 

In conclusion, if we look at microevolution as just the shuffling of alleles, it doesn’t equal macroevolution.

 

Which is why I resist definiing evolution solely in terms of "changing allele frequencies". Speciation involves other processes such as population isolation, change in habits, and fixation and loss of alleles My original argument was that all dog breeds were just the result of gene shuffling and that no beneficial mutation of a gene has been documented. If this is our definition of microevolution, it is not the same as macroevolution. If we introduce mutations, and we would have to look at the genomes to find them, than the two become the same thing.

 

When I think about it a bit more, maybe I am wrong. What is the genome of two species other than different alleles? We can transfer a gene from a fly into the mouse and have it function as normal... There is no "different" genes, just "different combinations of genes". Hmmm... now that I think about it, I am wrong.

 

Not entirely. There are also different genes. Remember gene duplication and chromosome duplication. These create new genes. Also, insertion and deletion mutations can change a gene so that it really has no functional relationship to the original allele.

[Quentin]

I've always thought that separating evolution into macro and microevolution is nonsense. There is a unique evolution. The evolution is not the selection of different combinaisons of allels. This combinaison of allels creates diversity in species. Mixing different allels doesn't create new species.

The evolution is supported by the modifications of our DNA, the mutations (deletion, duplication...)

Who are we to say that something is microevolution, and something else is macroevolution ? It's just a problem of scale. Evolution is a continuous phenomenon.

In France (you probably saw that my english is not perfect ! ), in my Medical School, professors doesn't talk about these two concepts (micro and macroevolution), except one (of histology and cytogenetics), who is known to be a quite radical christian. This makes me think that making a difference with micro and macroevolution is a way to introduce genetics in the theory of creationism. Are people separating evolution into micro and macroevolution necessarily creationists ?

[Mokele]

Are people separating evolution into micro and macroevolution necessarily creationists ?

 

Not necessarily; they may have valid reasons, such as Gould's controversial notion of species-level selection occuring.

 

Also, they're often separated simply for convinience, so people working on fruitflies won't be confused with people working on Ordovician snails. But that's merely a convenience, not a real distinction.

 

Mokele

[lucaspa]

I've always thought that separating evolution into macro and microevolution is nonsense. There is a unique evolution. The evolution is not the selection of different combinaisons of allels. This combinaison of allels creates diversity in species. Mixing different allels doesn't create new species.

 

It can. In the mix and match and selection, some alleles will move to fixation (every individual has them) and some will be removed totally from the population. This shifts the bell-shaped curve of traits either right or left and can move it such that the new bell-shaped curve doesn't overlap the old one.

 

Who are we to say that something is microevolution, and something else is macroevolution ? It's just a problem of scale. Evolution is a continuous phenomenon.

In France (you probably saw that my english is not perfect ! ), in my Medical School, professors doesn't talk about these two concepts (micro and macroevolution), except one (of histology and cytogenetics), who is known to be a quite radical christian. This makes me think that making a difference with micro and macroevolution is a way to introduce genetics in the theory of creationism. Are people separating evolution into micro and macroevolution necessarily creationists ?

 

I agree that evolution is a continuous phenomenon. However, evolutionary biologists, for convenience, do talk about about micro vs macroevolution. Micro is shifts of alleles within a population that does not necessarily lead to a new species. Macroevolution is the trends of species in an evolutionary lineage. The evolution of the horse is macroevolution. The trend is toward larger size, fewer toes, and changes in teeth to eat tougher grasses. There are exceptions to the trend, where a speciation will make a new species in the horse family smaller, but those all ended as extinctions.

 

But you are correct it is creationists (not necessarily Christians) that really try to draw a hard and sharp line between micro and macro. The purpose is emotional and theological, not scientific or convenience. Creationists accept micro evolution but deny macro. IOW, they deny the sequence of individuals and speciations that led from a species of fish to amphibians, or from Hyracatherium to modern horses and zebras.

 

Microevolution is "changes within populations and species".*

Macroevolution is "the origin and diversification of higher taxa".

"Many biologists consider the study of species and speciation to constitute the bridge between microevolution and macroevolution."* Douglas Futuyma, Evolutionary Biology, pg 447, 1998

 

"But we must ask, what exactly are these genera, families, orders, and so on? It was clear to Darwin, and it should be obvious to all today, that they are simply ever larger categories used to give names to ever larger clusters of related species. That's all these clusters, these higher taxa, really are: simply clusters of related species.

 

Thus, in priniciple the evolution of a family should be no different in its basic nature, and should involve no different processes, from the evolution of a genus, since a family is nothing more than a collection of related genera. And genera are just collections of related species. The triumph of evolutionary biology in the 1930s and 1940s was the conclusion that the same principles of adaptive divergence just described -- primarily the processes of mutation and natural selection -- going on within species, accumulate to produce the differences we see between closely related species -- i.e., within genera. Q.E.D.: If adaptive modification within species explains the evolutionary differences between species within a genus, logically it must explain all the evolutionary change we see between families, orders, classes, phyla, and the kingdoms of life. Niles Eldredge, The Triumph of Evolution and the Failure of Creationism. pgs 76-77.

[Dak]

This makes me think that making a difference with micro and macroevolution is a way to introduce genetics in the theory of creationism. Are people separating evolution into micro and macroevolution necessarily creationists ?

 

as has allready pretty-much been said, they're useful terms for talking about evolution. certain things can contribute to macroevolution, but not microevolution, such as sexual isolation. i suppose you could say that the plague contributed hugely to microevolution, but not macroevolution, as it shifted the allele frequency of the delta-9 allele but didn't do anything to encorage speciation?

 

what creationists do, afaict, is assume a majical, undescribed, and completely invisable mechanism that limits how far from some kind of 'default plan' microevolution can take a creature, and also that prevents any of the other non-culmination-of-microevolutions mechanisms that we've actually observed causing speciation, thus allowing them (rather convieniently) to admit that microevolution is true, whilst maintaining that macroevolution is a big fat smelly pack of satanist lies.

 

as long as you bear in mind that theres no evidence for the above mechanism, and that microevolution X lots can = macroevolution, theres nothing 'unscientific' about the terms.

[lucaspa]

i suppose you could say that the plague contributed hugely to microevolution, but not macroevolution, as it shifted the allele frequency of the delta-9 allele but didn't do anything to encorage speciation?

 

As I understand it, yes. Macroevolution involves speciation. In fact, many evolutionary biologists equate those: macroevolution = speciation. The reproductive isolation of the !Kung -- including unique alleles in that population -- is incipient macroevolution, IMO, because the end result would be a new species of Homo.

 

what creationists do, afaict, is assume a majical, undescribed, and completely invisable mechanism that limits how far from some kind of 'default plan' microevolution can take a creature, and also that prevents any of the other non-culmination-of-microevolutions mechanisms that we've actually observed causing speciation, thus allowing them (rather convieniently) to admit that microevolution is true, whilst maintaining that macroevolution is a big fat smelly pack of satanist lies.

 

I basically agree. The distinction serves an emotional and theological function for creationists. Microevolution is so widely observed that they cannot deny it. However, they have to preserve, at all costs, the idea that "kinds" cannot transform to other kinds. So they created (intelligent design:-) ) this artificial distinction between micro and macro evolution. They will allow fluctuations of alleles within species as long as speciation doesn't take place.

 

Of course, then they have problems with that. They then admit that speciation occurs but try to draw a line with the slippery word "kinds". Look at the diagram on this page -- http://www.answersingenesis.org/home/area/magazines/docs/v22n3_liger.asp -- and compare it to the (only) diagram in Origin of Species. As far as I can see, they are the same!

 

as long as you bear in mind that theres no evidence for the above mechanism, and that microevolution X lots can = macroevolution, theres nothing 'unscientific' about the terms.

[CPL.Luke]

the easiest way to concoct anexample of macroevolution is to just seperate a species into two populations, and then apply a selection pressure on one population to develop radically different sex organs.

 

for instance if you selected for very large penises and very large vagina's, then eventually the two populations could no longer breed merely because the mechanics wouldn't work out.

 

then you apply another selection pressure to the members of one of the new "species" to develop fur (because its cold) or to shrink in size (because there isn't enough food) or some other such thing you will soon have two very different species. If you continued to apply distinct selection pressures you could have entirely different categories of species.

[foodchain]

If you take a mutation rate as a constant, I don’t know if organism to organism if mutation rates happen to be constant or what the rates happen to be for specific specie to specie or other variables but lets just say we have a .001% rate of mutation overall per say a one year unit of time over a million years within a certain population I am sure such would compound into a larger degree of variance of course giving other variable such as if the changes happen to be fit enough in relation to again more variables to persist. It a short term look at things it might be why we have so much variance in say ants. Long term I am sure is what allowed say wasps to become ants under current understanding. Such is why there is no direct links to say a cow giving birth to a goat or something like that as an example and possibly why evolution has to be studied really over such a large span of time and why we are not so much genetically different then our closest ancestors.

[lucaspa]

Mixing different allels doesn't create new species.

 

It can. Remember, most variation in sexually reproducing organisms comes from recombination -- mixing alleles. Again, most macroscopic traits are polygenic -- they are the result of interplay between many different genes.

 

The evolution is supported by the modifications of our DNA, the mutations (deletion, duplication...)

 

The definition of evolution is very broad. If you mean "descent with modification" -- which is the best short-hand definition -- that evolution happens is partly supported by the fact that there are mechanisms to introduce changes (mutations) into our DNA. But mutations alone won't cause changes in species.

 

There is a type of natural selection called "stabilizing" or "purifying" selection. When a population is in a stable environment and is well-adapted, any change in DNA is going to move them off the fitness peak. In that case, natural selection is going to act to eliminate the "modifications of our DNA" and the population remains genetically stable.

 

Who are we to say that something is microevolution, and something else is macroevolution ? It's just a problem of scale. Evolution is a continuous phenomenon. ... Are people separating evolution into micro and macroevolution necessarily creationists ?

 

No. It is evolutionary biologists who came up with the terms "microevolution" and "macroevolution". Microevolution was coined to represent the changes seen in populations by population geneticists. A famous example would be the shift in coloring in the peppered moths in England. Macroevolution referred to the long term trends in lineages seen in the fossil record -- such as the transition in the horse lineage from a small, 5 toed species Hyracatherium (?) to the modern horse Equus that is large and has only 1 toe. Macroevolution involves multiple speciations but the questions are: what are the reasons for such large scale changes over time (and many species) within a lineage?

 

The point where micro and macro evolution meet is speciation. In fact, speciation is macroevolution. Speciation (particularly in sexually reproducing organisms) involves processes in addition to the shuffling of alleles seen in microevolution. In particular, speciation involves reproductive isolation of two populations. Speciation also often involves separation of 2 populations of the same species, either by geography or by lifestyle.

[lucaspa]

If you take a mutation rate as a constant, I don’t know if organism to organism if mutation rates happen to be constant or what the rates happen to be for specific specie to specie

 

There have been studies. The mutation rate is about 1 per genome or individual. So you are a mutant, I am a mutant, and everyone posting on this board has a mutation. The current human population is 6 billion or so people. So there are that many mutations.

 

The vast majority of mutations are neutral. That is, they neither help nor hinder the individual in the population. That is why most populations have such a huge reservoir of genetic variability among the individuals. Humans are unusual right now because we went thru a bottleneck about 150,000 years ago when there were only about 10-100 breeding pairs of humans -- not very many individuals and thus not much variation.

 

It a short term look at things it might be why we have so much variance in say ants.

 

This is different. Ants are a Family, which means there are a LOT of species of ants. It is this difference between species that you are calling "variance in ants". This is different than variance between individuals. Ants underwent what is called "adaptive radiation" and moved into a lot of vacant ecological niches (lifestyles), which is why there are so many different species.

 

Such is why there is no direct links to say a cow giving birth to a goat or something like that as an example and possibly why evolution has to be studied really over such a large span of time and why we are not so much genetically different then our closest ancestors.

 

Evolution happens to populations, not individuals. That's why you don't have cows giving birth to goats. Over generations, the character of the population gradually shifts until the new population is different enough from the old one to be called a new species. If you plot the number of individual on the y-axis vs the trait (such as length of incisors) on the x-axis, you get a bell-shaped curve. Over generations, evolution (particularly with natural selection) shifts that bell-shaped curve either right or left on the x-axis. Say we get a shift of the incisors becoming longer as the population adapts to eating meat. Eventually, the curve will have shifted enough to the right such that the individual with the shortest incisor in the new curve will still have incisors longer than the individual with the longest incisor in the old curve. Is that clear or did I just completely confuse you?

[foodchain]

There have been studies. The mutation rate is about 1 per genome or individual. So you are a mutant, I am a mutant, and everyone posting on this board has a mutation. The current human population is 6 billion or so people. So there are that many mutations.

 

The vast majority of mutations are neutral. That is, they neither help nor hinder the individual in the population. That is why most populations have such a huge reservoir of genetic variability among the individuals. Humans are unusual right now because we went thru a bottleneck about 150,000 years ago when there were only about 10-100 breeding pairs of humans -- not very many individuals and thus not much variation.

 

 

 

This is different. Ants are a Family, which means there are a LOT of species of ants. It is this difference between species that you are calling "variance in ants". This is different than variance between individuals. Ants underwent what is called "adaptive radiation" and moved into a lot of vacant ecological niches (lifestyles), which is why there are so many different species.

 

 

 

Evolution happens to populations, not individuals. That's why you don't have cows giving birth to goats. Over generations, the character of the population gradually shifts until the new population is different enough from the old one to be called a new species. If you plot the number of individual on the y-axis vs the trait (such as length of incisors) on the x-axis, you get a bell-shaped curve. Over generations, evolution (particularly with natural selection) shifts that bell-shaped curve either right or left on the x-axis. Say we get a shift of the incisors becoming longer as the population adapts to eating meat. Eventually, the curve will have shifted enough to the right such that the individual with the shortest incisor in the new curve will still have incisors longer than the individual with the longest incisor in the old curve. Is that clear or did I just completely confuse you?

 

No, I got it. The polymer changes in small fashions which the comes to express overtime in the population from individuals of that population breeding. I think though to escape from saying that such is how it works, thus why evolution is such a long and slow process overall in regards to our perception is because a cow wont ever birth such a radical amount of change as a goat, or that statistically or some other numerical formula I think goes to support evolution being a slow gradual process based on the population through such functions like sexuality.

 

I though thought that different types of mutation had different rates, like hotspots or what not? I mean does the Y chromo have a different rate of mutation or pressures then the X? I also am unsure how compartmentalization and homeostasis has to do with this. I read a small article on inter contest evolution, if I have the term right or ICE for short, I would think it odd to say lump mutation into one single factor unless it was various factors going over a population under observation and it being based on genome in total but that would be of course just population genetics. I would think that such a practice has some downfalls simply from the lack of direct observation in all levels biologically such as the individual, something medicine seems to lack most the time.

[lucaspa]

No, I got it. The polymer changes in small fashions which the comes to express overtime in the population from individuals of that population breeding.

 

That doesn't make any sense to me. Please try again. What polymer? What is "express overtime in the population"?

 

I think though to escape from saying that such is how it works, thus why evolution is such a long and slow process overall in regards to our perception is because a cow wont ever birth such a radical amount of change as a goat, or that statistically or some other numerical formula I think goes to support evolution being a slow gradual process based on the population through such functions like sexuality.[/quote

 

Again, Since evolution works on populations, it is the population that changes over generations. Since larger animals have generation times from 1 year on up, this means that very few generations happen within a human lifetime. That is why evolution looks "slow" to us. Experiments using bacteria -- which have generation times of about 20 minutes -- show considerable evolution over the course of time we are able to devote to experiments.

 

One of my favorite examples of speciation is a study done in Drosophila. It took 5 years. That is an incredibly long time for scientific research! Five years before you can publish a paper? Five years of taking care of dozens of bottles of Drosophila each and every day?

 

I though thought that different types of mutation had different rates, like hotspots or what not? I mean does the Y chromo have a different rate of mutation or pressures then the X?

 

There are stretches of the DNA that are more prone to mutation than other stretches. Those are "hotspots". When we say "types of mutations" we mean substitution, addition, deletions, duplications, translocations, etc. And yes, subsitutions, deletions, and additions of single nucleotides are more common. But the mutation rate comprising all types of mutations on any spot in the genome is about 1 per person.

 

I would think it odd to say lump mutation into one single factor unless it was various factors going over a population under observation and it being based on genome in total but that would be of course just population genetics. I would think that such a practice has some downfalls simply from the lack of direct observation in all levels biologically such as the individual, something medicine seems to lack most the time.

 

Again, we are talking rate of mutations per individual. That automatically lumps all mutations together. The paper was looking at a flatworm C. elegans. They picked this because the worms are hermaphrodite, so they could compare populations that descended from a single individual. So they had a baseline genome -- the hermaphroditic parent -- as a starting point.

 

Now, I'm not sure what you mean by "lack of direct observation in all levels biologically". Biology is about direct observation at all levels, from the genome to populations. A hot area in medicine is "single nucleotide polymorphisms" (SNPs or "snips") which is looking at single nucleotide differences in a single gene between individuals. This is often related to particular diseases. So what I see in medicine and biology is direct observation -- at least as much in other sciences if not more. In physics, for instance, subatomic particles are never directly observed. What is observed is their effects on other things.

[foodchain]

noun

(biochemistry) a long linear polymer found in the nucleus of a cell and formed from nucleotides and shaped like a double helix; associated with the transmission of genetic information; "DNA is the king of molecules" [syn: deoxyribonucleic acid]

 

Sorry, my bad on that one.

 

Yes, evolution works within populations, I am not trying to argue on this. My point is that the change does not occur in some universal shift all it once in the population is all. As such is simply just using a population as the only marker truly good enough to reflect the reality of evolution and the mechanisms behind it. Overall I think on an individual level much could be gained. To follow that we evolved would imply that such could be traced, which it is of course, on many levels such as fossils, or the pattern that leads to cephalization to simply the fact we all have dna or what not. To simply just stay at arms distance though with populations is a bit of a problem to me because populations are made up of individuals for the most part right? So what if say you have the same specie but one population is in a part of India and the other is in say New York, would you just assume that because you know that mutation rate in India is .1% that such is the same in the population in New York? For that matter what on an individual level, is it .1% for every individual. I mean if you stretch the questions out pretty soon I think you would find just looking at it from a population level simply does not suffice overall.

 

I also agree that evolution appears slow to us because a radical amount of change I doubt ever occurs save for maybe deleterious forms overall. That minor changes over time add into big changes as you go farther in time, such as again my example that evolution has to be studied over a very long period of time, not that last week we evolved from toads or something.

 

I also think that in physics we don’t directly view sub atomic particles because we might not have the ability to directly view them as maybe we would like, save for in atom smashers or what not. Overall I trust direct observations and validations of such via repetitiveness, this is all. The problem as I see it is that in real time with biology you cant have the mathematical rigidness that you can find in simply math with an example of 1 +1 equals two and to attempt such would surely lead to nothing more then fallacy. With the experiments I read involving simple organisms mutation, the rates of and success of for the matter in various cycles in the same environment causing the change never produced a pattern or a repeat for the matter.

[lucaspa]

noun

(biochemistry) a long linear polymer found in the nucleus of a cell and formed from nucleotides and shaped like a double helix; associated with the transmission of genetic information; "DNA is the king of molecules" [syn: deoxyribonucleic acid]

 

Sorry, my bad on that one.

 

So you meant DNA, not "polymer"? Now, what did you mean by "express overtime in the population"? You do know there are lots of polymers, don't you? Protein is a polymer of amino acids.

 

Yes, evolution works within populations, I am not trying to argue on this. My point is that the change does not occur in some universal shift all it once in the population is all. As such is simply just using a population as the only marker truly good enough to reflect the reality of evolution and the mechanisms behind it. Overall I think on an individual level much could be gained. To follow that we evolved would imply that such could be traced, which it is of course, on many levels such as fossils, or the pattern that leads to cephalization to simply the fact we all have dna or what not. To simply just stay at arms distance though with populations is a bit of a problem to me because populations are made up of individuals for the most part right?

 

To start with the question at the end: No, working with populations is not staying at "arms distance" since it is the characteristics of the population that changes in evolution. Yes, populations are made up of individuals, but individuals stay the same through their lifetimes. Individuals are born with their genome, and that genome doesn't change during the lifetime of the individual. So, from the perspective of evolution, individuals are constant. Populations change.

 

With a directional change in environment, yes, there is a "universal shift". In a climate growing colder, there is a directional shift in the character of the population toward longer fur. Now, that doesn't mean that all deer are born with longer fur. Instead, just as many deer are born with shorter fur as longer fur, but only the longer furred ones survive. Natural selection shifts the population over the course of generation. Any population has characteristics in a bell-shaped curve. In the case of our hypothetical deer, we would have a bell-shaped curve with a center (mean) of 1 cm length of hair (fur). But the range would be from, say, 0.5 cm to 1.5 cm. However, in the colder winter, only those deer with fur 1 - 1.5 cm survive. Thus, the next generation now has a new bell-shaped curve with a mean of 1.25 cm and a range of 0.8- 1.7 cm (you still get some deer born with shorter and longer fur). The next winter is even colder and only those deer with fur 1.1 to 1.7 cm survive. Now the next generation has a bell-shaped curve from 1.0 to 1.8 cm with a mean of 1.4 cm. Do you see how the population is changing over time? Yes, each generation still has individuals with 1 cm length fur, but we've lost all those deer with 0.5 cm and now have new deer with 1.8 cm.

 

What we get at the individual is the variation within the population. And it is the variation that natural selection acts on.

 

Natural selection acts on the individual, and an individual is either lucky or unlucky in the alleles it is dealt at birth. If it is dealt a set of alleles that do well in that particular environment, then that individual is selected. If not, then the individual -- and that set of alleles -- is eliminated.

 

So what if say you have the same specie but one population is in a part of India and the other is in say New York, would you just assume that because you know that mutation rate in India is .1% that such is the same in the population in New York? For that matter what on an individual level, is it .1% for every individual. I mean if you stretch the questions out pretty soon I think you would find just looking at it from a population level simply does not suffice overall.

 

Since mutations are due to universal biochemical and chemical mechanisms, yes, the mutation rates are the same. And yes, the different studies have been done on Drosophila in widely separated locations: the US and Europe, for instance. And the results have been the same.

 

Now, remember that the mutation rate was determined by looking at hundreds or thousands of individuals. Always in biology what you get is a mean ± the standard deviation. For the sake of simplicity, usually only the mean is reported, but don't be fooled. Basically, the mutation rate would be 1% ± 0.1. Which means that 2.5% of individuals will have a mutation rate < 0.98% and 2.5% will have a mutation rate > 1.2%

 

I also agree that evolution appears slow to us because a radical amount of change I doubt ever occurs save for maybe deleterious forms overall. That minor changes over time add into big changes as you go farther in time, such as again my example that evolution has to be studied over a very long period of time,

 

Large changes are, as you say, usually accumulations of small changes. There are exceptions. If you have changes in the Hox genes -- control genes in development, you can have major changes in the organism. For instance, a change in the Manx gene makes a tail. And a change in just one nucleotide in the Ubx gene goes from the multiple legs of the millipede to the 6 legs of an insect.

 

However, we have at least 2 ways of looking at "farther in time" in evolution. One is to look at existing related species and see the intermediate steps of evolution. A recent study looked at the evolution of the placenta and a genus of fish as a series of intermediate steps from species to species within the genus:

David N. Reznick, Mariana Mateos, and Mark S. Springer Independent Origins and Rapid Evolution of the Placenta in the Fish Genus Poeciliopsis Science 298: 1018-1020, Nov. 1, 2002. http://www.u.arizona.edu/~mmateos/reznicketal.pdf News article at: http://www.sciencemag.org/cgi/content/full/298/5595/945a

 

Another example is the family of skinks. The entire family is intermediate between lizards and snakes and shows the decreasing length of legs from lizards to snakes.

 

And, of course, there is the fossil record. Sometimes the record is complete enough that there are series of transitional individuals (and enough individuals to do the bell-shaped curves) connecting large evolutionary changes. three such studies are:

 

5. PR Sheldon, Parallel gradualistic evolution of Ordovician trilobites. Nature 330: 561-563, 1987. Rigourous biometric study of the pygidial ribs of 3458 specimens of 8 generic lineages in 7 stratgraphic layers covering about 3 million years. Gradual evolution where at any given time the population was intermediate between the samples before it and after it.

1. Williamson, PG, Paleontological documentation of speciation in cenozoic molluscs from Turkana basin. Nature 293:437-443, 1981.

1. McNamara KJ, Heterochrony and the evolution of echinoids. In CRC Paul and AB Smith (eds) Echinoderm Phylogeny and Evolutionary Biology, pp149-163, Clarendon Press, Oxford, 1988 pg 140 of Futuyma. This one shows the diverging bell-shaped curves.

 

There are many instances of observed speciation, some with quite large changes in characteristics of the populations.

 

The problem as I see it is that in real time with biology you cant have the mathematical rigidness that you can find in simply math with an example of 1 +1 equals two and to attempt such would surely lead to nothing more then fallacy.

 

Actually, you do have such mathematical rigidness. The equations of population genetics derived from Mendelian genetics are very rigid and very deterministic.

 

With the experiments I read involving simple organisms mutation, the rates of and success of for the matter in various cycles in the same environment causing the change never produced a pattern or a repeat for the matter.

 

The studies you have read are not "organisms mutation", but natural selection at work. You are thinking of the peppered moth and the Grant study of the beaks of finches on the Galapagos. There you have directional selection within a cycling environment. IOW, you don't have the same environment but an environment that changed one way, and then went back.

 

In the peppered moth the environment changed with industry and the darkening of birch bark with pollution. So natural selection picked the dark colored moths (whether by predation or some other mechanism) and the population shifted from mostly light colored moths and very few dark colored ones to mostly dark and very few light colored ones. Then the environment changed back before the dark color could be fixed and the light color eliminated. So the proportion of light to dark moths shifted back.

 

In the Grant study, it's not as simple as it looks. Looking only at the gross size of the beaks, yes, the population shifted from small to large beaks and then back to small beaks. But looking at detailed measurements of shape, the new small beaks are not the same as the original. Yes, they are small again, but they are different.

 

In experiments where the environment has changed and not changed back, natural selection has shifted the population and it has stayed there. A good example is this study: 1. Case, TJ, Natural selection out on a limb. Nature, 387: 15-16, May 1, 1997. Original paper in the same issue, pp. 70-73 (below).

JB Losos, KI Warheit, TW Schoener, Adaptive differentiation following experimental island colonization in Anolis lizards. Nature, 387: 70-73,1997 (May 1)

1a. JB Losos, Evolution: a lizard's tale. Scientific American 284: 64-69,March 2001. Phenotypic plasticity and evolution of Anolis lizards.

 

In this study lizards were introduced to various islands in the Bahamas. These islands had different types of vegetation -- different constant environments. The length of the limbsof the lizards varied from island to island 5 years after the introduction. The limb length varied according to the plant life present on the individual islands. Because the environment is constant, the change is constant.

[foodchain]

http://www.sci.sdsu.edu/~smaloy/MicrobialGenetics/topics/mutations/fluctuation.html

 

Mutation rate sheet

 

http://mbe.oxfordjournals.org/cgi/content/full/19/1/85

 

Here is two links that I found. In such I find that mutation simply is not as rigid as it may come out to be one viewed from a population biology perspective. I would also like to point out again for what we can gain from studying life from a population angle is great, its only so much of the picture overall.

 

I am interested in the underlying mechanism (which I imagine are many an dynamic) of such and as such I find that with math its not so rigid yet, though that could be from not knowing fully also.

 

Here is another link of interest to me.

 

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=310490

 

Understanding the biology from a total view, such as molecular and cellular is just as important to me as from a population perspective for total understanding, and in like many cases such is an interdisciplinary method.

 

Here is a neat article to articulate my point.

 

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=552327

 

And one more.

 

http://aob.oxfordjournals.org/cgi/content/abstract/mcl153v1

 

I think the reality is as I understand it currently far more complex then we simply grasp at this point and again simply cannot be fully understood through just population means alone, not to say population biology is not important its very important in my eyes just that it alone will not in total solve for the questions posed about evolution in total.

 

We need a tree of life to represent many angles such as the appearance or change to homeostasis, chemicals, just about everything over all. Like within a specie, its not so simple to go and compare what proteins are in one, compared to a similar specie. Say for Protists, we cant compare specie to specie on various degrees of difference such as protein appearance or changes in homeostasis or other various functions in some mapped our and accessible way, we also cannot access some geographic database to take into account other considerations such as food viability and temperature or even the average water current. I have my goals in college currently set on biochem, but I really wonder if I wont try to go into GIS at some point to press interdisciplinary methods of research.

 

On a side note my use of the word expression was to simply mean that genetics express in the organism, such as hair color.

[lucaspa]

http://www.sci.sdsu.edu/~smaloy/MicrobialGenetics/topics/mutations/fluctuation.html

 

Mutation rate sheet

 

http://mbe.oxfordjournals.org/cgi/content/full/19/1/85

 

Here is two links that I found. In such I find that mutation simply is not as rigid as it may come out to be one viewed from a population biology perspective.

 

What about these articles do you think supports your argument?

 

From the first site:

"What is the typical rate of spontaneous mutations?

Rates of spontaneous mutation seem to be determined by evolutionary balances between the deleterious consequences of many mutations and the additional energy and time required to further reduce mutation rates. Bacteria, Archae, and Eukaryotic microbes produce about one mutation per 300 chromosome replications. For E. coli this works out to be between 10-6 and 10-7 mutations per gene per generation, however it is important to note that there are certain "hot spots" or "cold spots" for spontaneous mutations. (A "hot spot" is a site that has a higher rate of mutations than predicted from a normal distribution, and a "cold spot" is a site with a lower rate of mutations than predicted from a normal distribution.) Higher eukaryotes have the same rate of spontaneous mutation, so that rates per sexual generation are about one mutation per gamete (close to the maximum compatible with life). RNA viruses have much higher mutation rates -- about one mutation per genome per chromosome replication -- and even small increases in their mutation rates are lethal."

 

So, bacteria, eukaryotes, and RNA viruses have different mutation rates. But within each category, the mutation rates are constant. Which is what I said all along. Notice the sentence I put in italics. It is what I said to begin with.

 

I would also like to point out again for what we can gain from studying life from a population angle is great, its only so much of the picture overall.

 

But both the articles you quoted were looking from a population perspective. IOW, both took the mutations in a POPULATION and then went from there to the average rate per individual.

 

I am interested in the underlying mechanism (which I imagine are many an dynamic) of such and as such I find that with math its not so rigid yet, though that could be from not knowing fully also.

 

Here is another link of interest to me.

 

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=310490

 

Understanding the biology from a total view, such as molecular and cellular is just as important to me as from a population perspective for total understanding, and in like many cases such is an interdisciplinary method. Here is a neat article to articulate my point.

 

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=552327

 

From the article: "These viruses circulate within infected hosts as vast populations of closely related, but genetically diverse, molecules known as "quasispecies". "

 

Did you see that? "Vast populations"

 

Now, somehow you have gone from my simple statement that evolution happens to populations to "Understanding the biology from a total view, such as molecular and cellular is just as important to me as from a population perspective ". No one ever said that the individual was not important, but simply that evolution doesn't happen to the individual. Evolution happens to populations.

 

And one more.

 

http://aob.oxfordjournals.org/cgi/content/abstract/mcl153v1

 

Again, did you read the paper? From the Abstract in the Methods section: "Methods F1, F2 and F3 generations were obtained through reciprocal crosses between stf and normal plants."

 

Did you see that? "generations", "plants". Both plural. They are studying the population.

 

I think the reality is as I understand it currently far more complex then we simply grasp at this point and again simply cannot be fully understood through just population means alone, not to say population biology is not important its very important in my eyes just that it alone will not in total solve for the questions posed about evolution in total.

 

First, again, evolution happens to populations, not individuals. This is not disputable because the data is overwhelming. And of course the reality is very complex because we are trying to simplify things so that you can understand. We are not presenting the totality of complexity to you because are missing the simple points.

 

Second, when you say "questions posed about evolution in total", what do you mean? Do you mean questions about whether evolution happned? About how evolution happens? Or about whether evolution can explain the diversity of life on the planet?

 

We need a tree of life to represent many angles such as the appearance or change to homeostasis, chemicals, just about everything over all.

 

We have a "tree of life". It represents that ancestor-descendent relationships among species.

 

Like within a specie, its not so simple to go and compare what proteins are in one, compared to a similar specie. Say for Protists, we cant compare specie to specie on various degrees of difference such as protein appearance or changes in homeostasis or other various functions in some mapped our and accessible way,

 

Yes, that has been, and is continuing to be done. By 2D gel electrophoresis, proteins between species have been compared. In fact, amino acid sequences between species have been compared.

1a. Cytochrome c differences in amino acids: http://members.aol.com/SHinrichs9/descent/denton.jpg

 

This compares the protein cytochrome c across species to species.

 

Look at the title of the paper below:

7. SA Chervitzet al. Comparison of the complete protein sets of worm and yeast:orthology and divergence. Science 282: 2022-2027, 11 Dec. 1998

 

we also cannot access some geographic database to take into account other considerations such as food viability and temperature or even the average water current.

 

Also been done:

13. JF Banfield and CR Marshall, Genomics and geosciences. Science287: 605-606, Jan 28, 2000. Discusses cladistics to help map evolution of microorganisms and relate this to changes in geochemistry.

 

I have my goals in college currently set on biochem, but I really wonder if I wont try to go into GIS at some point to press interdisciplinary methods of research.

 

You don't have to "press", you simply have to join. The interdisciplinary approach is already being used. Look at the one above: genomics and geology.

 

Here's one looking at ecology, medicine, and evolution:

6. Ecology and evolution of infection. Science 292: 1089-1122, May 11, 2001.

 

Here, these are good evolution sites:

http://www.aaas.org/spp/dser/evolution/

http://evolution.berkeley.edu/

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookEVOLII.html

http://www.swarthmore.edu/NatSci/cpurrin1/evolk12/evoops.htm

 

On a side note my use of the word expression was to simply mean that genetics express in the organism, such as hair color.