Creationism and Genetics


#1

What follows is the result of months of research and debate. I have believed for some time that Darwinism is an unnessacary part of evolutionary biology. What has happened is the Darwinism has been blended with Mendelian genetics in something they call the modern synthesis. What follows is actually an experiment in evidential apologetics and I am interested in you insights, comments and other thoughts on the signifigance of this for Christian Apologetics.

Let us ponder the the most signifigant questions confronting the single common ancestor model in our day. What makes us human? (Nature 437, 69-87 ) What is the genetic basis for the threefold expansion of the human brain in 2 1/2 million years?(Genetics, Vol. 165, 2063-2070) What is the genetic and evolutionary background of phenotypic traits that set humans apart from our closest evolutionary relatives, the chimpanzees?(Genome Research 14:1462-1473)

One of the problems with the evolutionary expansion of the human brain from that of an ape is the size, weight and complexity. The human brian would have had to triple in size, starting 2 1/2 million years ago and ending 200 to 400 thousand years ago. The brain weight would have had to grow by 250% while the body only grows by 20%. The average brain weight would have to go from 400-450g, 2 1/2 MY ago to 1350–1450 g 0.2–0.4 MY.

“It is generally believed that the brain expansion set the stage for the emergence of human language and other high-order cognitive functions and that it was caused by adaptive selection (DECAN 1992 ), yet the genetic basis of the expansion remains elusive.”

Evolution of the Human ASPM Gene, a Major Determinant of Brain Size, Genetics, Vol. 165, 2063-2070, December 2003

Jianzhi Zhang tried to determine if positive selection of amino acid substitutions that left the reading frame open are detectable in the ASPM gene. He instead found strong purifying selection and concluded that the postive selection of the ASPM gene took place time between 6–7 and 0.1 MY ago (0.5 x 10,000 generations x 20 years/generation). Researchers have determined that the gene is still evolving but I wonder how a congenital developmental defect characterized by severely reduced brain size could be an advantage.

Overall genetic differences create a problem since the size of the genetic differences is growing. Type ‘DNA simularities between humans and chimpanzees’ into a google search engine and you will find estimates close to 99%. Growing evidence has determined that these estimates are just plain wrong. The divergance has been found to include indels of considerable length, in the comparision of the Chimpanzee Chromosome 22 and its counterpart Human Chromosome 21 found that 83% of chimpanzee chromosome 22 proteins are different from their human counterparts.

“Sakaki said their analysis found about 68,000 insertions or deletions. “That is almost one insertion/deletion every 470 bases,” he said. In addition, a small proportion of genes showed a relatively higher rate of evolution than most other genes. “We haven’t known what proportion of the genes shows adaptive evolution. This study shows it to be about 2 to 3%,” he said.”

Chimps are not like humans Whole-chromosome comparison reveals much greater genetic differences than expected

More recently, the Chimpanzee Genome project published their highly anticipated Initial sequence of the chimpanzee genome and comparison with the human genome, Nature 437, 69-87 (1 September 2005). What they found was the the differences between the chimpanzee and human genomes have a 35 million nucleotide difference with five million insertion/deletion events, and various chromosomal rearrangements. This would include a 3 million bp divergance in the function part of the genome effecting vital functions.Even by conservative estimates the fixation of single base substitutions, insertions, deletions and polymorphisms (including chromosomal rearrangements) would have to average anywhere from 3 to 7 bp differences, fixed in the respective geneomes, per year for humans to evolve from apes.

Feel free to offer whatever questions or comments you feel are appropriate. This is actually a part of a larger discussion and I am just interested in you thoughts regarding the signifigance of this kind of research in Apologetics.

Grace and peace,
Mark


#2

Interesting post. Microevolution obviously occurs. This is justified by common sense and a basic understanding of genetics. Microevolution poses no threat to either belief in God or the Bible.

Macroevolution poses a bigger threat. I’ve never been entirely convinced by the argument for macroevolution. I don’t doubt it for moral/theological reasons, but simply because it doesn’t seem to make sense. I could accept macroevolution if there were some positive force driving it forward. This force would obviously be “God-controlled”, but could express itself in the physical world by something as simple as DNA understanding efficiency. Our own bodies are capable of adapting to make themselves more efficient, so I don’t see it as too much of a stretch of the imagination.

One thought regarding the chimpanzee thing. God institutes the human soul. This supernatural change alters human nature and leads to grammar. This also brings with it the anomolous expansion of the brain. If this is true, I have no problems with it because regardless of how close other species get to us, they would have to have a soul instituted by God to become “persons”, so we don’t need to be worried.

Just thinking out loud.


#3

[quote=mark kennedy]…Feel free to offer whatever questions or comments you feel are appropriate. This is actually a part of a larger discussion and I am just interested in you thoughts regarding the signifigance of this kind of research in Apologetics.

Grace and peace,
Mark
[/quote]

Mark
It looks like you put a lot of work into this but I’m not sure what relation it has to apologetics?
what is your goal?

AFAIK the Church has not put forward any pronouncements on the various debates within genetics that you cited (nor should She) and Catholics are free to accept the modern syntheses (and evolution) or not.

Is there debate in science? Sure
Does that affect the overall framework in which they debate? No.

Should the discovery of one more or one less gene affect one’s faith? No.

As for human brain size. I’m not an expert but I’m sure why the size, weight and complexity are a particular issue. The limit on brain size is the size of the birth canal. The changes in the hip when we adopted bipedalism allowed for the increase in size.

As for the selective pressure that favored it……I don’t know I wasn’t there and it probably changed over time. but I can say that a brain can be a handy thing sometimes.

Brains are handy but they are expensive to grow. So unless you have something to do with that big brain there is probably no pressure to grow one. The fact that we already had opposable thumbs on the ends of limbs that weren’t used for walking, in addition to binocular vision and an omnivorous diet certainly helped the process along. Call it blind chance, serendipity, or the Hand of God but we did grow big(ger) brains regardless of the mechnism.


#4

Honestly, this is not surprising. Let’s just do some back-of-the-envelope calculations:
Assuming a 1.5% DNA sequence difference between humans and chimps, a protein of 500 amino acids (encoded by 1500 base pairs) will, on average, have 10 nucleotides different between the human and chimp. Unless each of these nucleotide differences is a synonymous mutation (that is that the codon still encodes for the same amino acid) there will be a change in the amino acid sequence. Thus it is not surprising to me that there are 83% of the proteins that are not identical in humans and chimps. What is more surprising is that 17% of the proteins are identical! Notably, though, the 83% of the proteins that show a difference will probably have very little difference at the amino acid level.
In fact, if you read the original paper that this note is based on you’d see:

From Nature Magazine
For those 179 genes, the average nucleotide and amino acid identity in the coding region is 99.29% and 99.18%, respectively.

That is to say that even though 83% of the proteins differ between humans and chimps, they only differ in less than 1% of their amino acids.
And I’ll wager that the vast majority of the changes are between similar types of amino acids and are not in the active sites of the proteins in question.
But the main point is that this research in no way contradicts evolution, and if anything it shows just how similar chimps and humans are.
JRM


#5

What I meant to say was a 1% DNA difference over 1500 base pairs would have 15 nucleotides different. Just typed too fast.
JRM


closed #6

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