Evidence for the Evolutionary Model

Amino Acid Differences Between Chimp & Human Proteins

Creationist claim:

"Humans have 200,000 [proteins]. 80% of our [proteins] do not exist in apes! Yes, 80% (Gene volume 346 14 February 2005, Pages 215-219). Biochemically, we are so different, that any such assumption is science fiction." --micah1116

      This is a particularly misleading characterization of the Glazko (2005) study, due to its phraseology, and due to the fact that actually reading it (rather than just looking at the title and abstract) makes it clear that what it reports is the exact opposite of the conclusion drawn above.

      The publication does not say that "80% of our [proteins] do not exist in apes;" rather it says that 80% don't have identical sequences of amino acids (big difference). As the publication states:

"In terms of nucleotide differences, the human is closer to the chimpanzee than to any other hominoid species. The early genome comparison by DNA hybridization suggested a nucleotide difference of 1–2% [references omitted]. Recently, direct nucleotide sequencing confirmed this estimate [references omitted]. However, a large portion (about 98%) of the human genome is known to be non-protein-coding DNA, and the estimate of 1–2% nucleotide difference is largely based on the comparison of non-protein-coding DNA, which has little effect on phenotypic characters (Glazko et al., 2005, p.215)."

So they decided to compare protein-coding regions:

"...we compiled 127 human and chimp orthologous proteins (44,000 amino acid residues) from GenBank. Only 25 (20%) of these proteins showed the identical amino acid sequence between humans and chimpanzees. In other words, the proportion of different proteins was 80%, in contrast to the 1–2% difference at the nucleotide level (Glazko et al., 2005, p.215)."

      But the question that some creationists hope you won't ask is how much different did they find those 80% of proteins to be? Answer: unexpectedly little...

"Even the 80% protein differences appear to be too small to explain the phenotypic differences. It seems that the phenotypic differences are controlled by a small proportion of genes, either by regulatory genes or by major effect genes (Glazko et al., 2005, p.218)."

 

 

      So not only are 20% identical, but the 80% that are different are still so similar that much of the genetic basis for the phenotypic differences must be due to regulatory sequences and/or genes that have major effects.

      This is what happens when people quote mine the titles and abstracts of research publications, rather than actually reading them and examining the data they present

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Reference:

Glazko, G., V. Veeramachaneni, M. Nei, and W. Makałowski. "Eighty percent of proteins are different between humans and chimpanzees." Gene 346 (2005 Feb 14): 215-9. <http://www.ncbi.nlm.nih.gov/pubmed/15716009>.