Define evolution

[Jet Black]

no many of them are not Christians becaue they oftern teach the opposite to what the BIBLE teaches us.

ok, let me put this challenge to you: Are Lucaspa and sfs Christians?

 

[Jet Black]

Aron-Ra how can you say Christians are bias when you say that you are bias.
and the evolutionist are bias because they try tell people that micro-evolution is true, as I have no question with that as people see it happen, but then the evolutionist says that because that is true then macro-evolution must be true as well.
Which I dont agree with as no person has ever seen or experienced.

what's macroevolution then?

 

[sfs]

No. Genetic drift acts within a population. It does not split a population.

You two seem to be talking past each other. Genetic drift does not create two populations out of one. But if geographical isolation creates two populations, then genetic drift will eventually cause reproductive isolation as well, and two species will result. The process is likely to be much slower than if selection is involved, however.

 

[sfs]

But mutations don't "accrue" unless there is selection. Remember Hardy-Weinberg. Gene frequencies stay the same from generation to generation unless there is some other process acting. The equations for genetic drift shows that it is not a factor when the effective population size >50.

No, that's not right. Strictly speaking, Hardy-Weinberg is only accurate for infinite population sizes; for any finite population, genetic drift will be a factor. Even in infinite populations, genetic drift causes most new beneficial alleles to disappear from the population. For most realistic population sizes, genetic drift also causes new neutral mutations to fix. One of the most basic results of population genetics, in fact, is that the rate of fixation of neutral alleles is independent of population size (assuming a constant-sized population at equilibrium). For example, the great bulk of mutations that have accumulated between humans and chimpanzees (a subject that often comes up here) are almost certainly selectively neutral.

 

[CACTUSJACKmankin]

Aron-Ra how can you say Christians are bias when you say that you are bias.
and the evolutionist are bias because they try tell people that micro-evolution is true, as I have no question with that as people see it happen, but then the evolutionist says that because that is true then macro-evolution must be true as well.
Which I dont agree with as no person has ever seen or experienced.

If you can explain to me what the barrier is between microevolution and macroevolution, apart from time which there is plenty of, I'd like to see it.

 

[Aron-Ra]

no many of them are not Christians becaue they oftern teach the opposite to what the BIBLE teaches us.

Then the question is; do you worship God? Or do you worship a book men wrote about God?

Aron-Ra how can you say Christians are bias when you say that you are bias.

But I did not say I was biased. In fact, I said I was not biased.

and the evolutionist are bias because they try tell people that micro-evolution is true, as I have no question with that as people see it happen, but then the evolutionist says that because that is true then macro-evolution must be true as well.
Which I dont agree with as no person has ever seen or experienced.

Macroevolution has in fact been directly-observed and documented dozens of times, both in the lab and in naturally-controlled conditions in the field. I can provide documentation for many of these occuracnces if you wish.

Once again, "evolutionists" (legitimate scientists) are not biased as the practice of scientific methodology tends to restrict that. But creationists are biased and admittedly so.

 

[Split Rock]

yes but you must remember that national geographic is a bias magazine and that they are evolutionists

What does swarm theory have to do with evolution? Obviously group behavior evolved, but other than that, what is your point?

 

[Split Rock]

You two seem to be talking past each other. Genetic drift does not create two populations out of one. But if geographical isolation creates two populations, then genetic drift will eventually cause reproductive isolation as well, and two species will result. The process is likely to be much slower than if selection is involved, however.

Yes, that was my point. Thanks for making it more clear.

 

[lucaspa]

no many of them are not Christians becaue they oftern teach the opposite to what the BIBLE teaches us.

Didn't God create? Then Creation is just as much God as the Bible. Why are you saying that only the Bible can be true and deny God's Creation?

EVOLUTION IS NOT ATHEISM

Over half of all evolutionary biologists have been theists, the vast majority Christians.

and the evolutionist are bias because they try tell people that micro-evolution is true, as I have no question with that as people see it happen, but then the evolutionist says that because that is true then macro-evolution must be true as well.
Which I dont agree with as no person has ever seen or experienced.

Define "macroevolution" and what you think it means.

Macroevolution has been seen in the fossil record in that there are several instances where transitional individuals are seen that connect species to species to new genera, family, order and class. I listed some of them here: http://www.christianforums.com/t43227

Now, we have observed speciation in real time. Actually, we have also observed speciation making several new species that are a new genus.

Since higher taxa are nothing more than collections of species, it's obvious that the processes (microevolution) that give rise to new species will also give rise to all the higher taxa. And we have seen the consequences of macroevolution. Remember, the present is the way it is because the past was the way it was. What we see now could not exist unless macroevolution happened in the past.

"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.

 

[lucaspa]

You two seem to be talking past each other. Genetic drift does not create two populations out of one. But if geographical isolation creates two populations, then genetic drift will eventually cause reproductive isolation as well, and two species will result.

Not "eventually". The probability that genetic drift will "fix" an allele (or eliminate it) are actually quite low.

Mathematics. Futuyma page 393

Kimura and then Li and Gauer derived the probability of an allele being fixed in the population. The probability of fixation of an allele A2 where the fitness of the genotypes are: A1A1 = 1, A1A2 = 1 +s, and A2A2 = 1 +2s is:

P = 1 - e^2Nsq/1 - e^-4Nq where e = the base of natural logarithms = 2.718, N = effective population size, s = selection coefficient, and q = the initial frequency of the allele in the population. For a mutation, q = 1/2N

Where s = 0 (genetic drift) then the equation reduces to P = 1/2N. At N =50, you are already down to P = 0.01.

That's for one allele. For speciation, you need several allelic changes to get a new species. So start multiplying the probabilities and you quickly get to the level that it is VERY unlikely that genetic drift is going to cause speciation.

 

[lucaspa]

My point was that you were ignoring genetic drift, which is the dominant contributor to evolution in many situations.

As the previous post shows, genetic drift is only significant (and not even dominant) when you have VERY small population sizes: less than 50 effective breeding individuals (25 couples).

Perhaps my difficulties arise from picturing genes as individuals.

I submit it is a confusion between "selection OF" and "selection FOR". It is selection OF the individual, but selection FOR the allele.

The HWE is based on the assumption that alleles are inherited independtly of each other which isn't true for every allele. Also, HWE is violated for small founding populations which can be involved in allopatric speciation (eg founding populations on islands).

Yes, Hardy-Weinberg involves some assumptions. As the equations in the post above and later in this post show, genetic drift can become significant in small founding populations, even leading to fixation of traits that are slightly deleterious.

I guess what I was going for is the causation of divergence. With sympatric speciation it is strongly influenced by genetics. This is what gets the ball rolling. For example, the case of the apple maggot where speciation occurs by adapting to different hosts and hence different breeding periods. The two step process is adaptation then isolation. I view allopatric speciation as the opposite trend, isolation followed by adaptation.

Even in your example of sympatric speciation, isolation comes FIRST. Genetics comes later. First the population is isolated on its new host, then that new host is a new environment and natural selection works adapting the population.

Ecosystems are the product of evolution.

Only partly. They are also a product of the inorganic environment.

I never meant that the Modern Synthesis is more restrictive.

What I said was that people tend to try to make the Modern Synthesis more restrictive than it actually is. They tend to say that the MS does not include evo-devo when it really does.

No, that's not right. Strictly speaking, Hardy-Weinberg is only accurate for infinite population sizes; for any finite population, genetic drift will be a factor.

Let's remember that "strictly speaking". The approach to pure stability of allelic frequency is asymptotic, so you can get VERY close to this in finite sized populations. Close enough that the existence of selection is determined by testing observations against Hardy-Weinberg. In statistical terms, Hardy-Weinberg is used as the "null hypothesis" when testing to see whether selection has happened.

Even in infinite populations, genetic drift causes most new beneficial alleles to disappear from the population.

You need to document this. Even with large populations, the probability of fixation of genes due to selection (beneficial alleles with s > 0) is very high. See below.

One of the most basic results of population genetics, in fact, is that the rate of fixation of neutral alleles is independent of population size (assuming a constant-sized population at equilibrium).

I have to look that one up tonight, because I don't think that's true. The rate of mutation is constant and independent of population size. That is what you are referring to in "the great bulk of mutations that have accumulated between humans and chimpanzees (a subject that often comes up here) are almost certainly selectively neutral." In fact, since the rate is measured in pseudogenes that are not expressed, they are by definition "neutral" since they are hidden from natural selection.

OK, let's do some numbers again:

Mathematics. Futuyma page 393

Kimura and then Li and Gauer derived the probability of an allele being fixed in the population. The probability of fixation of an allele A2 where the fitness of the genotypes are: A1A1 = 1, A1A2 = 1 +s, and A2A2 = 1 +2s is:

P = 1 - e^2Nsq/1 - e^-4Nq where e = the base of natural logarithms = 2.718, N = effective population size, s = selection coefficient, and q = the initial frequency of the allele in the population. For a mutation, q = 1/2N

Where s = 0 (genetic drift) then the equation reduces to P = 1/2N. The influence on fixation is obvious. Double the population and you halve the probability.

So, let's consider N = 50. The probability that an allele will be fixed becomes 0.01. Take N = 1,000 and the probability of fixation is 0.0005.

Let's take the same N = 1,000 and the selective advantage is small at s = 0.01 and A2 is a mutation so that its initial frequency is 1/2000, then P = 0.02. Compare that to P = 0.0005 for genetic drift. Which is more significant?

Where N is large (>100) and s is positive, then P = 2s. From this, the probability for fixation by selection becomes independent of population size.

So let's take our same s = 0.01 and N = 10,000. P is still 0.02. However, P from genetic drift is 0.00005.

Most s observed in nature range from 0.1 - 0.8. This means, of course that the probability of fixation due to selection ranges from 0.2 (1 in 5) to 1.0. When fixation probability is 1, I don't see how "genetic drift causes most new beneficial alleles to disappear from the population" can possibly be true.

 

[sfs]

Not "eventually". The probability that genetic drift will "fix" an allele (or eliminate it) are actually quite low.

Mathematics. Futuyma page 393

Kimura and then Li and Gauer derived the probability of an allele being fixed in the population. The probability of fixation of an allele A2 where the fitness of the genotypes are: A1A1 = 1, A1A2 = 1 +s, and A2A2 = 1 +2s is:

P = 1 - e^2Nsq/1 - e^-4Nq where e = the base of natural logarithms = 2.718, N = effective population size, s = selection coefficient, and q = the initial frequency of the allele in the population. For a mutation, q = 1/2N

Where s = 0 (genetic drift) then the equation reduces to P = 1/2N. At N =50, you are already down to P = 0.01.

That's for one allele. For speciation, you need several allelic changes to get a new species. So start multiplying the probabilities and you quickly get to the level that it is VERY unlikely that genetic drift is going to cause speciation.

The probability that any new neutral allele will fix is indeed 1/2N, and becomes very small for modest sized populations. The total number of neutral alleles that fix, however, does not decrease as the population size increases, because the number of mutations that occur also increase linearly with the population. In a diploid population, the total number of mutations is 2Nu, where u is the mutation rate per generation per genome copy. The probability that each fixes is 1/2N, so the mean number of neutral alleles fixing by drift is u per generation, regardless of population size. For mammals, u is on the order of tens of mutations per generation -- so that's how many neutral alleles fix by drift.

Of course, very few of those neutral alleles will cause incompatability with other populations, which is why I said the process is likely to be slow. I don't know what the fraction is, however, which is why I also suggested that the answer is not well understood.

 

[lucaspa]

so the mean number of neutral alleles fixing by drift is u per generation, regardless of population size. For mammals, u is on the order of tens of mutations per generation -- so that's how many neutral alleles fix by drift.

Of course, very few of those neutral alleles will cause incompatability with other populations, which is why I said the process is likely to be slow.

If the allele is neutral, it won't cause incompatibility, will it? Because it won't really change the phenotype. What you would need is a mutation that causes sexual incompatibility.

Mutation rates are usually very low. Humans have one of the highest at an estimated rate of 10-20 mutations per genome. E. coli is about 0.0001 per genome and Drosophila is 1 per genome, if I remember correctly.

You also need to consider the time it takes for any given mutation to be fixed by genetic drift. That definitely does depend on population size.

It turns out that the time is 4N generations. So, with a population size of 1,000 that would be 4,000 generations. With human generation time of 20 years, that would be 80,000 years! With our current population of 6 billion, the time for an allele to be fixed by genetic drift is going to be 480 billion years! The mutations being fixed in this generation would have originated 80,000 years ago!

Since most species only have a lifetime of a 1-2 million years, the species has gone extinct before genetic drift has had time to make them a new species.

Drosophila would fare better, with 4,000 weeks, or 80 years to be fixed. Since natural selection produced new species of Drosophila in 250 generations, genetic drift is still pretty insignificant.

 

[sfs]

Let's take the same N = 1,000 and the selective advantage is small at s = 0.01 and A2 is a mutation so that its initial frequency is 1/2000, then P = 0.02. Compare that to P = 0.0005 for genetic drift. Which is more significant?

The probability of an allele being fixed is obviously higher for a beneficial allele than for a neutral one. Beneficial alleles are much, much rarer than neutral ones, however, so the contribution of genetic drift to fixation is still much larger than that of positive selection. In humans, the total number of nonfunctional fixed differences with chimpanzees is several orders of magnitude larger than the number of functional differences.

Where N is large (>100) and s is positive, then P = 2s. From this, the probability for fixation by selection becomes independent of population size.

So let's take our same s = 0.01 and N = 10,000. P is still 0.02. However, P from genetic drift is 0.00005.

Most s observed in nature range from 0.1 - 0.8.

It's that last statement that is the source of the confusion (where did you get it from, anyway?). Most positive selection in nature
is thought to be driven by selection coefficients much smaller than this. s = 0.1 is considered very strong selection, and is very rare compared to s < 0.01. It might well be that most observed instances of selection are cases of very strong selection, but that's because there is a powerful effect of ascertainment: they're much easier to see than cases of weak selection.

 

[sfs]

If the allele is neutral, it won't cause incompatibility, will it? Because it won't really change the phenotype. What you would need is a mutation that causes sexual incompatibility.

Sure, neutral mutations can do that. Take a species that uses pheromones for mate recognition. Population A fixes a neutral variant that changes the olfactory receptor used to detect the pheromone. The new OR is just as sensitive (or even more sensitive) to the standard type of pheromone, but has greater selectivity: it doesn't bind closely related molecules as well. Population B fixes a neutral mutation in the pheromone. The ancestral OR receptor binds the new pheromone just fine, but the mutated OR in population B has trouble recognizing it.

That's the kind of thing that can (and will, given enough time) cause reproductive isolation. A single set of changes is unlikely to produce complete isolation, but can easily move things in that direction.

Mutation rates are usually very low. Humans have one of the highest at an estimated rate of 10-20 mutations per genome.

I haven't seen a published estimate that low in that last ten years. Typical estimates are in the range of 30 to 60 per genome.

E. coli is about 0.0001 per genome and Drosophila is 1 per genome, if I remember correctly.

You also need to consider the time it takes for any given mutation to be fixed by genetic drift. That definitely does depend on population size.

It turns out that the time is 4N generations. So, with a population size of 1,000 that would be 4,000 generations. With human generation time of 20 years, that would be 80,000 years!

Yes. And every generation fixes a new lot of alleles. Using your numbers, in 80,000 years 80,000 alleles will have fixed in that population. In another population, 80,000 alleles, many of them different, will also have fixed. In half a million years (roughly the time since the Neandertal line diverged from our line), there would be something like a million fixed differences. Is that enough to cause speciation? I don't know, but it's not obviously nuts.

With our current population of 6 billion, the time for an allele to be fixed by genetic drift is going to be 480 billion years!

Yes. Fixation by drift is not currently an issue for humans.

Drosophila would fare better, with 4,000 weeks, or 80 years to be fixed. Since natural selection produced new species of Drosophila in 250 generations, genetic drift is still pretty insignificant.

I agree. That's why I wrote, "The process is likely to be much slower than if selection is involved, however." Speciation driven by selection is probably the norm.

 

[Loudmouth]

I submit it is a confusion between "selection OF" and "selection FOR". It is selection OF the individual, but selection FOR the allele.

I submit that I have been working with bacteria for too long.

Even in your example of sympatric speciation, isolation comes FIRST. Genetics comes later. First the population is isolated on its new host, then that new host is a new environment and natural selection works adapting the population.

In the case of the apple maggot it was my understanding that two populations adapted to two different hosts which led to two populations that are reproductively active at different times of the year. It was the adaptation that led to a temporal isolation.

What I said was that people tend to try to make the Modern Synthesis more restrictive than it actually is. They tend to say that the MS does not include evo-devo when it really does.

I have seen that as well, and try to fix it when I can. The Modern Synthesis is a very, very large tent.

 

[FishFace]

no many of them are not Christians becaue they oftern teach the opposite to what the BIBLE teaches us.

Hey hey hey, this is Mr N. T. McScotsman knocking on your door. A Christian is someone, roughly, who believes in Christ, and his teachings. You can be a Christian and believe in evolution. You can be a Christian and (gosh!) believe that the Bible is fallible!

and the evolutionist are bias because they try tell people that micro-evolution is true, as I have no question with that as people see it happen, but then the evolutionist says that because that is true then macro-evolution must be true as well.

Macro-evolution is evidenced by dozens of different things, including morphology, atavisms, ERV hierarchy, Cytochrome C, pseudogenes and non-coding DNA.

Direct observation of microevolution tells us how macroevolution happens.

 

[s41nn0n]

ja exept that macro-evolution has never been seen and never will be by a human so how does one know that it can happen.
if you dont believe in Genesis or parts of it as it does clearly teach that the earth was created in 6 days. then what other parts of the Bible dont you "have" to believe?

 

[Skaloop]

ja exept that macro-evolution has never been seen and never will be by a human so how does one know that it can happen.

Do you have any reason why it couldn't happen?

if you dont believe in Genesis or parts of it as it does clearly teach that the earth was created in 6 days. then what other parts of the Bible dont you "have" to believe?

You don't have to believe any of it. Heck, you don't even really need to believe that Jesus existed. One could take his life as an fable, adhere to the teachings of that allegory, and technically be a follower of Christ (aka - A Christian).

 

[s41nn0n]

yes because it takes supposedly "millions and millions" of years and no man has ever stayed allive for that long in recorded history.