Freethought & Rationalism Archive

RufusAtticus · 06-24-2003, 07:23 PM

Quote:

Originally posted by caravelair
any references to back up those numbers?

Yes. I have a post somewhere on this forum where I calculate it.

Addendum:

Here is the repost of the work.

From some work I did on Christian Forums, in responce to Sean Pitman, who later incorporated it into his webpage without any reference to me:

Twenty three replications occur to form an ovum. At the onset of puberty the male germline stem cells have gone through an estimated 30 cell divisions and then one every 16 days there after. Then in sperm formation there are 5 more replications. (See figure 2 in the following paper). Therefore, sperm will have gone through anywhere from 35 to >900 cell divisions by the time they meet the egg. Clearly the number of point mutations an offspring has is mostly affected by the age of the father.

From, Crow JF. (2000) "The origins patterns and implications of human spontaneous mutation" Nature Reviews Genetics (1) pp40-47.

Quote:

Box 1 | Estimating the number of male germ-cell divisions
We can estimate the number of germ-cell divisions
in a male of age A as follows. There are an estimated
30 cell divisions before puberty and then one stem
cell division every 16 days, or 23 per year. Then,
before sperm formation there are four mitotic and
two meiotic divisions (one chromosome replication).
Letting NA be the number of germline chromosome
replications at age A,Np the number at puberty and Ap
the age at puberty, taken to be 15 years,
NA = Np + 23(A � Ap) + 4 + 1 = 35 + 23(A � 15).

This calculation gives the following results.
Age - Chromosome replications
15 - 35
20 - 150
30 - 380
40 - 610
50 - 840

So if we take 25 years as the mean generation time, NA = 265. Therefore the number of point mutations an offspring has compared to its parents can be calculated as follows.

Code:

# point mutations = # of maternal point mutations + 
                     # of paternal point mutations
# haploid mutations = # haploid base pairs * # replications *
                       rate of mutation per bp per replication

npm = mpm + ppm = hbp*mu*(mr+pr) = 
3.2 gbp*288 reps*(mu pms per bp per rep)*(1 billion bp/gbp)

If mu = 1e-10 point mutations per bp per replication (0.33 pms per human haploid set per replication), then offspring will inherit ~92 point mutations. And this is on the low end of our error rate.

If mu = 1e-9, then the offspring will inherit ~920 point mutations. And this is probably on the high end for a person with a 25 year old father.

If mu = 5.5e-10, then the offspring will inherit ~506 point mutations.

If mu = 3.16e-10, then the offspring will inherit ~291 point mutations.

Now Nachman and Crowell (2000)'s estimate of 2.5e-8 point mutations per nucleotide per generation gives an answer of ~160 point mutations (2.5e-8*6.4 gbp). This is clearly within the range prediced by the error rate per bp per replication.

Now considering that ~130 million babies are now being born every year, it's clear that it won't take 100,000 generations to get an advantageous point mutation.

RufusAtticus · 06-24-2003, 07:26 PM

Quote:

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.

Note that this is not a point mutation rate, but rather the rate at which an amino-acid is changed in a protein

Dr.GH · 06-24-2003, 09:02 PM

If anyone has a link to the Nilsson and Pelger paper on the evolution of the eye, it would clean up the question. There number of generations would be far fweer than the creationist's claim quoted above.

Quote:

Proc R Soc Lond B Biol Sci 1994 Apr 22;256(1345):53-58
A pessimistic estimate of the time required for an eye to evolve.

Nilsson DE, Pelger S

Department of Zoology, Lund University, Sweden.

Theoretical considerations of eye design allow us to find routes along which the optical structures of eyes may have evolved. If selection constantly favours an increase in the amount of detectable spatial information, a light-sensitive patch will gradually turn into a focused lens eye through continuous small improvements of design. An upper limit for the number of generations required for the complete transformation can be calculated with a minimum of assumptions. Even with a consistently pessimistic approach the time required becomes amazingly short: only a few hundred thousand years.

RBH · 06-24-2003, 10:00 PM

Dr. GH wrote

Quote:

If anyone has a link to the Nilsson and Pelger paper on the evolution of the eye, it would clean up the question. There number of generations would be far fweer than the creationist's claim quoted above.

Unfortunately it's apparently not on the Web. However, using very conservative assumptions about the variables involved, N&P concluded that an enclosed focused lens eye could evolve from a flat surface patch of photosensitive cells within 364,000 generations. Further, they showed that a selectable pathway (i.e., a pathway in which all of the small successive incremental steps increase visual acuity) exists between the flat patch of photosensitive cells and a fully-formed focused lens eye: no saltational jumps or even neutral 'stage-setting' mutations are required.

Since Nilsson & Pelger required that only one feature could change incrementally per step, their estimate is a maximum, not a minimum, since it ignores the real possibility of parallel coevolution of associated structures, which would reduce the number of generations required.

RBH

Jesus Tap-Dancin' Christ · 06-24-2003, 10:03 PM

Quote:

Originally vomited forth by someone who knows very little:
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.

Why? If he concedes that we aren't really an end, what difference does it make? Look at ANY end would be better.

Quote:

Let's use simple math.

And here's his first complete error. Simple math? On ANY system? Dear lord, bricks falling off of buildings don't involve very simple math--how the hell does he think entire biological processes involve "simple math"?

Quote:

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.

Why? Have you data?

Quote:

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.

Um.... NO. We have 100, from above. the 100,000 is a false application of multiplication error. He already gave the number of mutations necessary! The 1000 generations is another thing altogether--how long those mutations take to occur. The 100,000 therefore is utter nonsense.

Quote:

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.

Again, this is bad math--he already is using a FALSE number (through his own assumptions), and then creates a new one. We were already told it takes 1000 generations! WHICH IS IT?

Quote:

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.

Which is swell for a spherical chicken in a vacuum, but not so good for a large number of biological systems in a variety of environs, each competeing against each other.

Quote:

Anyway, at 1,000,000 generations, we get an eye.

1000 sir. From your initial statement.

Quote:

This, of course, is theoretically possible. We might have had enough time for that.

Given that it's .1% of what you said the second time around, sure.
By the way, in case you haven't seen it already, it's just fun from his statement of 1000 generations.

Quote:

But when you factor in the thousands upon thounds of changes that had to have taken place simultaneously, the chances get VERY slim.

Like, say, on the order of 1 in 3.256*10^324? 'Cuz I can create situations with those odds of occuring in 5 minutes. Oh, and I can create ones that are 500! (that's 500 factorial, or 500*499*498*...*3*2*1) times that by requiring specifics on the order of the dice I roll. Gee, I win!

Quote:

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.

Let's say not. Looks like he's GREAT now! He can see AND hear! That lucky bastard is better off than his forefathers were 1000 generations ago!

Quote:

Thus, the creature dies.

Or lives, as above.
[/quote]
Doubtlessly, it will suffer more from the negative mutation as its instincts are built on that ability already.
[/quote]
Or not.

Quote:

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.

So are the results of my dice rolling experiment. I doubt that you'd question it though.

Quote:

There are, without question, trillions upon trillions of more negative mutations than positive mutations.

Really? Are you sure about this number? Trillions upon trillions? Since you managed to confuse 1000 with 1000000, I'm beginning to doubt your mathematical capabilities seriously.

Quote:

For a positive mutation to work, it would have to work with NO OTHER NEGATIVE MUTATIONS.

Sickle Cell Anemia. This premise is therefore false.

Quote:

Also, this would have to happen frequently enough to create entire new species that cannot breed with one another.

No, not really. All it takes is one mutation to keep me from being able to breed with your sister.

Quote:

Which is the other model problem--the new gene would be lost in the gene pool.

Not really, due to developmental factors, and the fact that the building blocks already exist in the gene pool, and likely will be brought forth by the presence of another mutation.

Quote:

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.

No they aren't. Remember, when you consider that there are siblings, cousins, etc with similar genetic material, it's not likely to be lost in the time it takes that bad boy to get to breeding age.

Quote:

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.

Not necessarily again. Random doesn't always follow the statistical average--it just TENDS towards it.

Thread Tools	Search this Thread
Show Printable Version	Search this Thread: Advanced Search

Freethought & Rationalism Archive

The archives are read only.