Freethought & Rationalism Archive

caravelair · 06-23-2003, 03:02 PM

hi. i've been debating again. i was wondering what's the best way to deal with this type of argument:

Quote:

I have a problem with the entire general model in this way: it may be theoretically possible for random mutations to lead from no eye to a highly developed eye over tens of thousands of generations. However, that is only one aspect. There are thousands upon thousands--millions upon millions--of changes that have to take place for a protobacteria to become a human. Now, we are not looking for a specific target in the end, of course. But, we are talking about THIS end, so it is this end I am dealing with.

Let's use simple math. Lets say there are only 100 genes that have to mutate to go from no eye to a fully functional eye, and lets say it only takes 1,000 generations. Keeping in mind that the mutation is random (not the survival and passing on--this is non-random), we have to have, at minimal, 100,000 mutations to get the eye. Secondly, genes don't mutate very fast... not even 1 per generation. So let's just say every 10 generations we get a mutation. That's at least 1,000,000 generations. Of course, we have a a lot of tries going on at the same time, but this does not reduce the numbers, as we are still looking for a single, specific change, to get us where we are going. Also, I'm using very small numbers as is.

Anyway, at 1,000,000 generations, we get an eye. This, of course, is theoretically possible. We might have had enough time for that. But when you factor in the thousands upon thounds of changes that had to have taken place simultaneously, the chances get VERY slim. Let's say the eye and ear were evolving at the same time. In one individual, the eye makes a beneficial mutation, but the ear makes a negative mutation. Thus, the creature dies. Doubtlessly, it will suffer more from the negative mutation as its instincts are built on that ability already.

And so, when we have millions of mutations trying to happen at the same time, the chances of a line evolving far enough is pretty far fetched. There are, without question, trillions upon trillions of more negative mutations than positive mutations. For a positive mutation to work, it would have to work with NO OTHER NEGATIVE MUTATIONS. Also, this would have to happen frequently enough to create entire new species that cannot breed with one another. Which is the other model problem--the new gene would be lost in the gene pool. Dawkins scenerio doesn't work. He proposes new species gets geographically cut off from the parent species and is thus free to evolve, but this doesn't work because they very first genes are lost early on. And, you have to explain how only the new species is seperated. If any of the parent species goes along also, the genes will still mix again and we get back to the same state.

i've already asked him to back up his numbers with some type of evidence, and pointed out that his "simple math" is far too simple to accurately represent anything in nature. but i'm sure many of you on this board would think of errors in this that i would miss. as my aim is to completely inihilate his arguments, i would appreciate your input! thanks.

pz · 06-23-2003, 03:12 PM

So in his 'model', the population size is always 1?

Peez · 06-23-2003, 03:35 PM

One obvious error that jumps out at me is that they seem to be assuming only one individual per generation. Why not start with a simple animal that has a one-week life cycle and no eyes. We can follow it until it is a very similar animal that has well-developed eyes. Your debater seems like they would accept some fine-tuning between the eye of the latter animal and that of a human.

Our little eye-less animal lives in the ocean, along with 100 billion others of its species (this is not a particularly large population). Let us accept the dubious numbers given: 100 genes that require 1,000 mutations each (who knows where people come up with these numbers), so about 100,000 mutations. Mutation rates have been estimated to be on the order of 1 in 10^-10 per nucleotide per individual. For the sake of argument, let's go with 300 amino acids per protein, so about 1,000 nucleotides per gene, or about 100,000 nucleotides that may become involved in the eye. With the mutation rate given, this means that about one in 10^5 individuals would have a relevant mutation.

Thus, assuming that the population started with no genetic variance at these genes, we would expect about 100 billion x 10^-5 or about 1,000,000 relevant mutations per week, or in a modest period for the evolution of an eye, say 20 million years, about 10^14 relevant mutations. Remember that only 10^5 were needed. In fact, even if we think in terms of simple point mutations, this means that each nucleotide in each gene has been changed an average of 10^9 times!

Another obvious error made is the idea that a rare mutation that makes the eye better might happen to occur in an individual that just happened to have a gene that made the ear worse. This is silly on its face. What are the odds that these two mutation occur in the same individual? Well, only one in 10^5 individuals got an eye mutation. If the occurrence of crappy ear mutations was 1 in 100, then they would occur together in only 1 in 10^7 individuals. So what? Even if that unlucky individual dies, this will have virtually no effect on the numbers above (of course it might not). Remember that the genes for an improved eye and the genes for an improved ear do not have to be in the same individual because of sexual reproduction. Ain't sex grand!

Peez

caravelair · 06-23-2003, 03:59 PM

thanks, that was extremely helpful!

Doubting Didymus · 06-23-2003, 04:50 PM

Quote:

Originally posted by pz
So in his 'model', the population size is always 1?

Well, to be fair, he did say:

"Of course, we have a a lot of tries going on at the same time, but this does not reduce the numbers, as we are still looking for a single, specific change, to get us where we are going."

In other words, there might be lots of other individuals, but that doesn't matter because bing tiddle tiddle bong and the numbers are small as they are, biscuit barrel.

Don't be so quick to judge in future.

Asha'man · 06-23-2003, 07:54 PM

I seem to recall, posted somewhere on this forum, that the average human has around 5 mutations somewhere in their genome. Most of these are neutral or unnoticed.

That would also drasticly change the numbers, since you don't need to wait 10 generations for a change to be found.

I also think that the advantage of sexual reproduction is being overlooked. Given two mutations that affect separate traits (eye and ear, for example), those genes will eventually be distributed among the population (assuming neither mutation is instantly fatal). This easily allows selection to remove clusters of negative mutations, while clusters of positive mutations have a much stronger advantage.

The_Unknown_Banana · 06-23-2003, 08:53 PM

Quote:

Originally posted by Doubting Didymus
In other words, there might be lots of other individuals, but that doesn't matter because bing tiddle tiddle bong and the numbers are small as they are, biscuit barrel.

Don't be so quick to judge in future.

LOL!

Monty Python right?

RufusAtticus · 06-24-2003, 04:21 AM

Quote:

Originally posted by Asha'man
I seem to recall, posted somewhere on this forum, that the average human has around 5 mutations somewhere in their genome. Most of these are neutral or unnoticed.

No the average human inherits hundreds of point mutations from his parents, that arrose after his or her parents were conceived. Most of these will be neutral. Many will be deleterious. And perhaps a scant will be advantageous.

caravelair · 06-24-2003, 08:51 AM

any references to back up those numbers?

Jimmy Higgins · 06-24-2003, 10:18 AM

As to where that number 5 came from... maybe.

Quote:

Eyre-Walker and Keightley2 have made the analysis feasible by concentrating on protein-coding regions. They measured the amino-acid changes in 46 proteins in the human ancestral line after its divergence from the chimpanzee. Among 41,471 nucleotides, they found 143 nonsynonymous substitutions ? mutations where swapping one DNA base for another changes an amino acid, and therefore the final protein made by that gene. If these had evolved at the neutral rate, 231 would be expected. The difference, 88 (38%), is an estimate of the number of deleterious mutations that have been eliminated by natural selection and have therefore made no contribution to contemporary populations.

Translating these numbers into mutation rates gave a total rate of 4.2 mutations per person per generation, and a deleterious rate of 1.6. The rates for chimpanzees and gorillas were very similar, the deleterious rates being 1.7 and 1.2, respectively. The authors took 60,000 as the gene number and 25 years as the generation length. The number 1.6 is probably an underestimate, for various reasons. For instance, mutations outside the coding region are not counted and some of these regions ? such as those controlling gene expression ? are expected to be subject to natural selection. The gene number may also be an underestimate. If there have been mutations that increase fitness, they would also cause the number of deleterious mutations to be underestimated. A less conservative, and probably more realistic, estimate doubles the value, giving 3 new deleterious mutations per person per generation.

Nature 397, 293 - 294 (1999); doi:10.1038/16789
The odds of losing at genetic roulette
JAMES F. CROW
James F. Crow is in the Department of Genetics, University of Wisconsin, Madison, Wisconsin 53706, USA.

06-23-2003, 07:54 PM	#6
Asha'man Veteran Member Join Date: Dec 2001 Location: southeast Posts: 2,526	Sexual reproduction I seem to recall, posted somewhere on this forum, that the average human has around 5 mutations somewhere in their genome. Most of these are neutral or unnoticed. That would also drasticly change the numbers, since you don't need to wait 10 generations for a change to be found. I also think that the advantage of sexual reproduction is being overlooked. Given two mutations that affect separate traits (eye and ear, for example), those genes will eventually be distributed among the population (assuming neither mutation is instantly fatal). This easily allows selection to remove clusters of negative mutations, while clusters of positive mutations have a much stronger advantage.

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06-23-2003, 03:12 PM	#2
pz Veteran Member Join Date: Aug 2001 Location: Morris, MN Posts: 3,341	So in his 'model', the population size is always 1?

06-23-2003, 03:35 PM	#3
Peez Veteran Member Join Date: Apr 2001 Location: Canada Posts: 5,504	One obvious error that jumps out at me is that they seem to be assuming only one individual per generation. Why not start with a simple animal that has a one-week life cycle and no eyes. We can follow it until it is a very similar animal that has well-developed eyes. Your debater seems like they would accept some fine-tuning between the eye of the latter animal and that of a human. Our little eye-less animal lives in the ocean, along with 100 billion others of its species (this is not a particularly large population). Let us accept the dubious numbers given: 100 genes that require 1,000 mutations each (who knows where people come up with these numbers), so about 100,000 mutations. Mutation rates have been estimated to be on the order of 1 in 10^-10 per nucleotide per individual. For the sake of argument, let's go with 300 amino acids per protein, so about 1,000 nucleotides per gene, or about 100,000 nucleotides that may become involved in the eye. With the mutation rate given, this means that about one in 10^5 individuals would have a relevant mutation. Thus, assuming that the population started with no genetic variance at these genes, we would expect about 100 billion x 10^-5 or about 1,000,000 relevant mutations per week, or in a modest period for the evolution of an eye, say 20 million years, about 10^14 relevant mutations. Remember that only 10^5 were needed. In fact, even if we think in terms of simple point mutations, this means that each nucleotide in each gene has been changed an average of 10^9 times! Another obvious error made is the idea that a rare mutation that makes the eye better might happen to occur in an individual that just happened to have a gene that made the ear worse. This is silly on its face. What are the odds that these two mutation occur in the same individual? Well, only one in 10^5 individuals got an eye mutation. If the occurrence of crappy ear mutations was 1 in 100, then they would occur together in only 1 in 10^7 individuals. So what? Even if that unlucky individual dies, this will have virtually no effect on the numbers above (of course it might not). Remember that the genes for an improved eye and the genes for an improved ear do not have to be in the same individual because of sexual reproduction. Ain't sex grand! Peez

06-23-2003, 03:59 PM	#4
caravelair Regular Member Join Date: Apr 2003 Location: toronto Posts: 420	thanks, that was extremely helpful!

06-24-2003, 08:51 AM	#9
caravelair Regular Member Join Date: Apr 2003 Location: toronto Posts: 420	any references to back up those numbers?

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