DNA Homology: When 1% Discrepancy is Way Too Much

The following...

Setup
So, you may have heard it said quite often: we must be part-chimp because we have so much in common in our DNA with them. Right? Well, PBS show after PBS show, devoid of solid evidence, reiterates this same line ad-nauseum until it makes as many believers as possible. But how scientific is this claim, really?

Body
How much do we really have in common with chimps? In a Lansing State Journal editorial, one man was even emphatic that our DNA and that of chimps is 99% identical. But how many experts even agree on this figure? According to Don Batten of Answers in Genesis, the figure changes depending on who's telling the story: 96.2% being the original figure, with the figure dipping to 95% and then suddenly up to 97% and all the way up to the current guess of 99%.

In all of this, it begs the question: just how important is the difference, even if it seems so marginal? A group of researcher as Cornell University, firm believers in human-chimp ancestry, remark that "over 6 million" years or so, the amounts of "lifestyle changes" between us and chimps are radical. This has led them to question exactly how important even 1% difference in DNA similarity really is.

The team studied what would happen if human DNA were compared with chimp DNA in a test lab, and added mouse DNA to the test just for fairness. In addition to discovering that nearly all animal life has strong DNA homology, they discovered that at least **7,645** genes between us and the animal kingdom are radically different.

In related studies, they discovered that in just 1% difference, the structure of ears and how they are wired is radically different. According to one of the researchers, the difference in aural interpretations between us and chimps is "like replacing the soundboard of a Stradivanius violin with a piece of plywood...{in the end}...just 1% difference makes us completely different beasts". **⁵**

Brad Harrub and Bert Thompson, both with PhD's, of Apologetics Press, strongly dispute even the 99% homology figure. They have had at least this much to say: **⁶**

"The claim of 98% similarity between chimpanzees and humans is not only deceptive and misleading, but also scientifically incorrect. Today, scientists are finding more and more differences in DNA from humans and chimps.  For instance, a 2002 research study proved that human DNA was at least 5% different from chimpanzees—and that number probably will continue to grow as we learn all of the details about human DNA…"

These same skeptical doctors also point out that several chromosome structures resulting from the slight genetic variation between us and chimps result in chromosomes in chimps that are nowhere-present in man. **⁷**

Throughout the duration of the article, they continue to give even more examples of how the common-knowledge homology argument is, to say the very least, very misleading about the nature of life itself.

From a religious/philosophical standpoint, Don Batten argues that it only makes sense that all animal and human life would have strong commonality in DNA structure: **⁸**

"'If humans were entirely different from all other living things, or indeed if every living thing was entirely different, would this reveal the Creator to us? No! We would logically think that there must be many creators rather than one. The unity of the creation is testimony to the One True God who made it all…'"

Batten also argues that even in manufacturing, the 99% morphological or biochemical similarities in two things makes a lousy argument for evolution. He gave an example of how the Porche and Volkswagen are two very different cars, even though they have relatively identical chemical makeup structures and nearly all the same parts. **⁹**

To seal his argument against ape-to-man transition further, he points out the impossibility for random changes to ever account for the observed differences. He points out that just 4% difference in genetic structure of any two living things is the English-language equivalent of 40 encyclopedias-worth of radically different information, approximately the same as "12 million completely different words" formed over "120 million base pairs." **¹⁰**

In case anyone continued to doubt his claims on just how important these differences were, he showed how in the English language alone, often the addition or subtraction of just one word can radically alter the entire meaning of a given sentence. **¹¹** Such also it is with DNA.

Conclusion
All this being said, it is easy to see that the already time-worn argument of homology of any two creatures being an indication of ancestry requires a degree of similarity precision that simply cannot be accounted for when comparing two very different living things.

This would seem logical. Even from one human being to the next, with nearly identical DNA between two human beings, tissue rejection is still a major issue. The debate about human ancestry will continue in intellectual circles; but hopefully now everyone knows that sometimes, even being 99% certain of something simply isn't good enough.