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.”
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.”
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,