"After the union of sperm and egg (i.e. after fertilization), mammals
duplicate the genome about 50 times before producing sperm and egg in the
next generation. Because there are fifty duplications per generation, this
increases the *per generation* mutation rate by a factor of 50. My following
argument will ignore this 50-fold increase in mutation rate, thereby
*slowing* the increase of genetic variation. This assumption disfavors my
argument and therefore makes my conclusions more compelling. "
Walter, I think you err in your number of 50 divisions prior to the formation
of the next sperm cells. The human brain has 10^12 cells, (Scott Gilbert,
Developmental Biology (Sunderland: Sinauer, 1991), p. 172) The brain
represents about 1/10 of the human body so, we can expect that the body has
no more than 10^13 cells in it. If what you say is true then starting with a
single cell and dividing it 50 times, gives 2^50= 10^15 or 100 times the
number of cells I have in my body! So, before reaching sexual maturity, a
child must grow to be 10 times my size? What a football player!
If I recall your argument about Haldane's Dilemma (and admittedly I am rusty
with that argument) you say that evolution can not occur because in 1500
generations enough mutations would load the organism to destroy it. Wouldn't
your 50 additional steps make the continued survival of the human race at
risk now?
Thirdly, AND MOST IMPORTANTLY, the rates of mutation are not based upon that
observed by each cell division. We can't tell if a human cell has a mutant
form for two heads by looking at the cell. We can only tell when the child
is developed enough to see that there are two heads. So the rates are based
upon a PER GENERATION risk of mutation, not a PER CELL DIVISION rate! Thus
if you want to use the correct number then you need to divide the 10^--7 by
50 (I believe, it is quite late and I fear a math error) to arrive at the
correct rate per CELL DIVISION rather than the rate PER GENERATION.
Walter wrote:
>>The *haploid* mammalian genome (eg. a sperm or unfertilized egg) has around
3.5 billion nucleotides. Here is the math (2 x 3.5E9 / 1E7 = 700). That
amounts to 700 new mutations in each offspring! (A side note: If even a
substantial fraction of those are expressed, the standard model of
evolutionary genetics indicates the population would be in error
catastrophe. This, I say, is the unstated reason why evolutionists
concluded decades ago, long before we had done much genetic mapping, that a
high proportion, perhaps 97 percent or more, of the genome is inert and
functionless. By assuming a highly inert genome, they sought to make the
observed mutation rates compatible with the standard model of evolutionary
genetics. For details see my book.)<<
Notice in the above, even you use the term "per offspring".
You missed the point entirely. I asked how the number of alleles arose in
the time alloted by the YEC's An allele, being an alternative sequence for a
given gene location, it is irrelevant that 700 new mutations occur in the
entire genome. The issue is given a 1000 unit long region which codes for a
protein of approx 300 amino acids, what is the likelyhood that you will get a
mutation in THIS gene? Now, I agree that you can get a mutation in this
gene, but unless I am mistaken, most alleles are quite different in their
sequence from one another. If all alleles were only 10 substitutions
different from each other, then you might have a case, but if the allelic
sequences are substantially different, then there has not been enough time to
generate enough substitutions in this given 1000 unit long sequence.
Secondly, if what you say is true, then why do we not see evidence of ;this
in the historical record. Egyptian kittys are very very similar to the cat
in my house. Using your math, and using the 50 cell divisions (which I
showed was unreasonable) lets look at the kitty.
My streetwalking little kitty had her first litter when she was 9 months old.
Five months later she delivered her second litter. My wife and I decided to
have her fixed, but the vet said that we had to wait 8 weeks after she quit
nursing. Well, 8 weeks after she quit nursing, she delivered her third
litter! As near as we can tell she was playing around while she had her
children at home. Needless to say, we kept her indoors for those 8 weeks.
Using 9 months as the generation time, in the 5000 years since
Phaorahs first ruled Egypt, Cats have been through 6700 generations. And with
the 45 cell divisions (smaller number for a cat), there have been 6700 * 45=
301,500 chances for mutations to wipe the cat off the face of the earth or
evolve her more. Why have we not seen more change in them, or why have we
not seen the destruction which Walter would predict? Maybe because the
mutation rate is slower than what I estimated which exasperates the problems
for the YEC's. Because in order to avoid the problems on the ark, they have
only a few animals on board and then have them develop all the genetic
variability afterwards. Because Egyptian cats, dogs, jackals, ospreys,
ibis's are all like the ones we see alive today, I can only conclude that
evolution is much slower and that YEC's must believe in very rapid evolution
indeed.
Walter wrote:
>>
Let me clarify Glenn's statement for our readers. A typical gene is 1000
nucleotides in length. With a mutation rate of one in 1E7, the typical gene
would experience one mutation in 10,000 generations. <<
We agree on something. If the YEC view of the flood is correct, then there
have not even been 10000 generations since the flood. If there was a flood,
then it must have occurred a long, LONG time ago.
Walter wrote:
>>Here Glenn takes a human population (with a generation length of 20 years),
and he allots 4000 years (that's 200 generations) to produce genetic
variation. Then he makes a huge mistake. In effect, he has us take one gene
and duplicate it successively 200 times with a mutation rate of one per
10000, we then have ONE instance of the gene -- the 200th grand daughter of
the original gene. Then he calculates the probability that this ONE instance
of this one gene has suffered a mutation -- it is 0.02, a two percent chance.
He goes on to claim this is too low to explain the observed high levels of
genetic variation.
But Glenn misinterpreted the situation. To see his error let's again take
the above population of one million adults. Since they are diploids, there
are two million instances of the given gene. At one mutation per 10000,
there would be 200 new mutations of that gene EACH GENERATION! In 200
generations we would expect 40000 mutations to that gene. (Using Glenn's
"two percent" figure we get the same result: 2 million x 0.02 = 40000 new
mutations.) That makes for 40 thousand different versions of the gene, known
as "alleles". Yet Glenn asked for merely 59 alleles. <<
****
Walter, if I am not mistaken, you have really messed this one up. Each of
the million people have a history of 200 generations from Noah who represents
the genetic bottleneck.. That is all! I can not pass a mutation to you
and this is what your math wants me to believe. Your population number is
being used as if I make a copy of my genes, give them to you and you copy
them and give them to your neighbor who continues the process. After my
genes have been copied and passed through the entire population of Dallas,
you would be correct, there would be 40,000 mutations to that gene. But this
is NOT AT ALL how life operates!!!!! If it is, my biology teachers failed me
miserably..
Would anyone else care to comment on this? Do people really reproduce in
this fashion? If so, why have I always been left out of the party? :-)
glenn
16075 Longvista Dr.
Dallas, TX 75248