Claim CB144:

For years, evolutionists have hailed the chimpanzee as "our closest living relative" and have pointed out that the DNA is 98 to 99 percent identical between the two. Scientists now say the difference is 4 percent, double what they have been claiming for years.

Source:

DeWitt, David A. 2005. Chimp genome sequence very different from man. http://www.answersingenesis.org/docs2005/0905chimp.asp

Response:

  1. The difference between chimpanzees and humans due to single-nucleotide substitutions averages 1.23 percent, of which 1.06 percent or less is due to fixed divergence, and the rest being a result of polymorphism within chimp populations and within human populations. Insertion and deletion (indel) events account for another approximately 3 percent difference between chimp and human sequences, but each indel typically involves multiple nucleotides. The number of genetic changes from indels is a fraction of the number of single-nucleotide substitutions (roughly 5 million compared with roughly 35 million). So describing humans and chimpanzees as 98 to 99 percent identical is entirely appropriate (Chimpanzee Sequencing 2005).

  2. The difference measurement depends on what you are measuring. If you measure the number of proteins for which the entire protein is identical in the two species, humans and chimpanzees are 29 percent identical (Chimpanzee Sequencing 2005). If you measure nonsynonymous base pair differences within protein coding regions, humans and chimps are 99.75 percent identical (Chimpanzee Sequencing 2005, fig. 9). The original 98.4 percent estimate came from DNA hybridization experiments, which measured (indirectly, via DNA melting temperature) sequence difference among short segments of the genomes that are similar enough to hybridize but with repetitive elements removed (Sibley and Ahlquist 1987). Whatever measure is used, however, as long as the same measurement is used consistently, will show that humans are more closely related to chimpanzees (including the bonobo, sister species to the common chimpanzee) than to any other species.

    Note also, though, that evolution has not been uniform throughout the genomes, so estimates of human-chimp divergence which consider only part of the genome can give different results (Britten 2002, Chen et al. 2001).

References:

  1. Britten, Roy J. 2002. Divergence between samples of chimpanzee and human DNA sequences is 5% counting indels. Proceedings of the National Academy of Science USA 99: 13633-13635.
  2. Chen, F.-C., E. J. Vallender, H. Wang, C.-S. Tzeng, and W.-H. Li. 2001. Genomic divergence between human and chimpanzee estimated from large-scale alignments of genomic sequences. Journal of Heredity 92(6): 481-489.
  3. Chimpanzee Sequencing and Analysis Consortium. 2005. Initial sequence of the chimpanzee genome and comparison with the human genome. Nature 437: 69-87.
  4. Sibley, C. G. and J. E. Ahlquist. 1987. DNA hybridization evidence of hominid phylogeny: Results from an expanded data set. Journal of Molecular Evolution 26: 99-121.
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created 2005-9-28