Is the similarity in human/chimp DNA evidence for evolution?
Question: "Is the similarity in human/chimp DNA evidence for evolution?"
In recent years, genome mapping has enabled detailed comparisons between the DNA of humans and that of chimpanzees. Many have claimed that humans and chimpanzees share over 98% of their DNA. This is often taken as decisive evidence of the common ancestry of apes and humans. But is this argument tenable? Is this really a fact which definitively proves a human-chimp common ancestry? It is our contention that the percentage is misleading. In fact, when the data is examined more closely, the human-chimp genome comparisons turn out to contradict what would be predicted by evolution.
In reality, the genetic differences between humans and chimpanzees are probably greater than 2%. More recent studies have shown that the true genetic divergence between humans and apes is probably closer to 5%. Thus, the ďover 98% similarityĒ argument is probably an overstatement.
The differences between the DNA sequence of the human and the chimp are not distributed randomly throughout the genome. Rather, the differences are found in clusters. Actually, at those specific locations, the chimpís genome is similar to that of other primates. It is the human that stands out from the rest. Scientists often refer to these "clusters" as human accelerated regions (HARís) because the human genome supposedly shared a common ancestor with chimps. These HARís are located in DNA segments that do not code for genes. But this requires us to believe that evolution just so happened to cause such rapid change to occur in sites where those changes make an important difference in an organismís functioning necessary to ultimately create a human.
Such would be a whopper of a just-so story. But it gets better. Some HARís are found in DNA segments that do code for genes, and herein lies another multitude of difficulties. Evolution would predict that humans evolved from the chimp-human ancestor via natural selection acting on chance variations induced by mutations. However, recent research reveals just the opposite. The HARís that were found in protein coding genes showed evidence not of mutations that had been selected in view of their advantageous phenotype, but rather the exact opposite. The genetic changes showed evidence that they were, in point of fact, deleterious. They had become established in the population not because they provided some physiological advantage, but in spite of being deleterious. Such results make little sense within an evolutionary framework.
Clearly, the HARís show a trend in which the differences observed in the human DNA (as compared to similar species) typically increase the G-C content of that particular region of the DNA strand. Evolution would predict that the G-C content of the underlying gene should remain relatively constant, as natural selection picks out the DNA mutations that improve the protein. If evolution is true, therefore, we should not expect a consistent trend toward an increasing G-C content.
These HARís are not always limited simply to the protein coding part of the gene, but often extend beyond the border into the flanking sequences. This further suggests that these differences which are observed in the human DNA are not, in fact, consequences of natural selection enhancing the protein that the gene encodes. The HARís often tend to cluster in a single part of a gene, in and around a single exon (as opposed to across the entire gene), and they tend to correlate with male (but not female) recombination. Such observations make little sense in light of evolution.
In conclusion, as interesting as genetic similarities between chimpanzees and humans are, they are not evidence for Darwinism. Design is also able to explain them. Designers often make different products by utilization of similar parts, materials and arrangements. The common percentage pertains to the regions of our DNA that result in proteins. It makes more sense of the data for the Designer of nature to have used the same proteins to perform the same function in a variety of organisms.