JonF writes:
Your "understanding" is nonsense
from "Humans Are Not 98% Genetically Identical to Chimpanzees", lifesitenews.com:
"First, the 98% figure is probably overstated. An article in Science puts the actual figure at 94%. (Jon Cohen, "Relative Differences: The Myth of 1%, June 29, 2007). But even these figures are only measuring about 2% of our total genetic makeup - that is, those genes that code for proteins, the building blocks of our physical bodies and functions.
The vast majority of our DNA, known as "non-coding DNA" - sometimes called "junk DNA" because it was once thought not to have function - is very different in humans from most non-coding genes found in chimps and other apes. However, recent research has found that, contrary to previous belief, this repetitive DNA isn’t "junk" after all, but has distinct purposes."
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from "The Mismeasure of Man: Why Popular Ideas about Human-Chimp Comparisons Are Misleading or Wrong", evolutionnews.org:
"You have probably heard that our DNA, the stuff that makes us human, is only 1% different from chimps. The claim that we are little more than apes is now part of the Zeitgeist of our culture, having been propagated in the popular press for nearly forty years. However, that statement and the conclusions drawn from it are false.
Let’s look at the first claim, that we are only 1% different from chimps. That measurement only compares base changes in human and chimp DNA. It doesn’t include other kinds of changes to the DNA, like deletions and insertions or rearrangements. In addition, because of the sequencing methods used, repetitive DNA is not included.
Now that complete or nearly complete genome sequences for humans and chimps are available, a better picture of our differences and similarities is emerging. A 2007 essay in the journal Science, "Relative Differences: The Myth of 1%," says this (the pdf is here ):
Researchers are finding that on top of the 1% distinction, chunks of missing DNA, extra genes, altered connections in gene networks, and the very structure of chromosomes confound any quantification of "humanness" versus "chimpness."
To be specific, in addition to the 1% distinction already noted, entire genes are either duplicated or deleted between the two species, sometimes in long stretches called segmental duplications. Such duplications represent a 6.4% difference between chimps and humans. There are also insertions and deletions within genes, which affect the structure and function of the proteins they encode. That contributes another 3%, according to some estimates. And there are entirely new genes, specific to humans.
There are also changes that affect the timing and amount of gene expression. These changes include the insertion of new regulatory sequences upstream of genes. For example, some 6% of our genome is unique Alu insertions, as they are called. And Alu sequences are known to affect gene expression.
In addition, there are human-specific increases in DNA methylation that affect gene expression in the brain, and increased RNA modifications in the brain. These changes would not be detected by simply comparing DNA sequences. Yet they affect gene expression and interaction. Indeed, by one measure, 17.4% of gene regulatory networks in the brain are unique to humans.
Then there are DNA rearrangements. How genes are organized along chromosomes, and even the chromosomes structures themselves can be different. Our Y-chromosomes are strikingly different from those of chimps, for example. This was a surprise to researchers, given the relatively short time our species supposedly diverged from one another. Rearrangements are also not included in the 1% number, and are difficult to quantify.
It should be apparent that we are only beginning to discover important differences between chimps and us, so our numbers are incomplete. In fact, there is no clear way even to count the changes. Beyond that, we do not even know yet how many or which of these differences are functionally important. Perhaps not all are. However, it would be a mistake (one that has been made before) to assert that none of them are functionally significant, as the Encode project demonstrated.
From the same Science paper:
Could researchers combine all of what’s known and come up with a precise percentage difference between humans and chimpanzees? "I don’t think there’s any way to calculate a number," says geneticist Svante Pbo, a chimp consortium member based at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. "In the end, it’s a political and social and cultural thing about how we see our differences." [Emphasis added.]"
Edited by Dredge, : No reason given.
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