by Jeffrey Tomkins, Ph.D., & Brian Thomas, M.S.

A recent high-profile article in the journal Nature released the results of a study with implications that shocked the scientific community because they contradict long-held claims of human-chimp DNA similarity. A previous Acts & Facts article showed that much of the research surrounding the often touted claims of 98 percent (or higher) DNA similarity between chimps and humans has been based on flawed and biased research. The problem is that the similarity has been uncertain because no one has performed an unbiased and comprehensive DNA similarity study until now. And the results are not good news for the story of human evolution…

In the 2005 chimpanzee genome project and resulting Nature journal publication, the sequence contigs were not assembled and oriented based on a map of the chimpanzee genome, but rather on a map of the human genome. Given the fact that the chimpanzee genome is at least 10 percent larger overall than the human genome, this method of assembly was not only biased toward an evolutionary presupposition of human-chimp similarity, but was also inherently flawed…

Not only were the locations of DNA categories completely different between human and chimp, but so were their proportions. One sequence class, or category containing DNA with a characteristic sequence, within the chimpanzee Y chromosome had less than 10 percent similarity with the same class in the human Y chromosome, and vice versa. Another large class shared only half the similarities of the other species, and vice versa. One differed by as much as 3.3-fold (330 percent), and a class specific to human “has no counterpart in the chimpanzee MSY [male-specific Y chromosome].”

As far as looking at specific genes, the chimp and human Y chromosomes had a dramatic difference in gene content of 53 percent. In other words, the chimp was lacking approximately half of the genes found on a human Y chromosome. Because genes occur in families or similarity categories, the researchers also sought to determine if there was any difference in actual gene categories. They found a shocking 33 percent difference. The human Y chromosome contains a third more gene categories–entirely different classes of genes–compared to chimps…

Because virtually every structural aspect of the human and chimp Y chromosomes was different, it was hard to arrive at an overall similarity estimate between the two. The researchers did postulate an overall 70 percent similarity, which did not take into account size differences or structural arrangement differences. This was done by concluding that only 70 percent of the chimp sequence could be aligned with the human sequence–not taking into account differences within the alignments.

In other words, 70 percent was a conservative estimate, especially when considering that 50 percent of the human genes were missing from the chimp, and that the regions that did have some similarity were located in completely different patterns. When all aspects of non-similarity–sequence categories, genes, gene families, and gene position–are taken into account, it is safe to say that the overall similarity was lower than 70 percent. The Nature article expressed the discrepancy between this data and standard evolutionary interpretations in a rather intriguing way: ” Indeed, at 6 million years of separation, the difference in MSY gene content in chimpanzee and human is more comparable to the difference in autosomal gene content in chicken and human, at 310 million years of separation.”…

More… (source)

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