A Fresh Look at Human-Chimp DNA Similarity

Often scientific reports or mainstream media claim 99% identical comparisons between human and chimp genomes. The number has been dropping in some circles recently, but is still on the order of 95+%. There is inherent bias in these calculations because significant lengths of DNA that are quite different between the two species are omitted from the results. A very simplified comparison would be comparing blue jeans (pardon the pun) with cut-off jeans. The fact that the legs are missing on one is discounted and only the upper portion is compared, with particular emphasis on the comparison of the rivets, buttons, pockets, topstitching, and zipper, but not much comparison on the brand, color, or the quality of the fabric. In a similar way, gaps or missing portions (like the missing legs on the cut-off jeans) and regulatory portions (like the fabric) from one are typically ignored, and only gene-rich segments of DNA are analyzed (like pockets, buttons, and rivets). Taking all those things into account, in 2012 creationist scientists Drs. Tomkins and Bergman came up with an overall similarity of around 81% — quite a difference! Other researchers have come up with even lower percent similarity, averaging around 70%.2 In 2013, Tomkins tested alignment of each chimpanzee chromosome against its human counterpart and only found an overall genome similarity of about 70%, which was published in Answers Research Journal.

BLASTN Away at Percent Similarity

BLASTN, an online program (an algorithm, actually) that many scientists use to compare the sequence of DNA bases comprising the genomes of organisms, occasionally gets updated as any software. In 2014, a programmer reported a bug in BLASTN to Dr. Tomkins. At that point, Dr. Tomkins noticed that the most recent versions seemed to be omitting many results that weren’t at least 98% similar to the target human base sequences. Dr. Tomkins decided to investigate using six versions of this algorithm, including the recent versions in question. Additionally, he used two other common algorithms for DNA comparison, Nucmer and LASTZ.

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