As the battle between Darwinism and the Bible rages, some evangelicals have backed away from maintaining that Adam and Eve were real, historical individuals created in the way Genesis 2 relates. In a just-published article from the Westminster Theological Journal, Westminster Theological Seminary professor Vern Poythress brilliantly explains why such a surrender is wrong biblically and scientifically. Poythress, with both a Th.D. and a Harvard Ph.D. in mathematics, is well-positioned to write about both theology and evolutionary theory.
Adam versus claims from genetics
Did Adam and Eve exist? Does science say otherwise? The human genome project has produced voluminous data about the information contained in human DNA. Various news media and scientists tell us that this information demonstrates our ape ancestry. How do we evaluate these claims? Evaluation is important for theological reasons. As the claims based on genetics have mounted, the theological discussion about Adam has heated up. From people with biblical and theological training we hear the argument that we must revise our understanding of the Bible and theology because we have to accept that evolution is an established fact. In response, we hear the opposing argument that the Bible and theology call on us to retain the conviction that Adam was a historical individual whose fall into sin resulted in guilt and sin for all his descendants. On both sides, people with training in biblical studies have understandably avoided discussing in detail the character of the scientific claims, and yet these have obviously greatly influenced the side that has abandoned the traditional understanding of Adam. It is important to undertake a theologically informed evaluation of claims coming from genetics.
We cannot within a short compass examine all the claims and all the evidence in detail. But we can summarize some of the main points, and direct readers to more extensive information.
I. Ninety-nine percent common DNA
We may begin with a commonly cited statistic, the 99 percent identity between human DNA and chimp DNA. In 2005 the Cornell University News Service reported: “Chimpanzees and humans share a common ancestor, and even today 99 percent of the two species’ DNA is identical.” In 2010 the University of California at San Francisco News mentioned the same figure: “The genetic codes of chimps and humans are 99 percent identical.” In 2005 the National Institutes of Health News reported, “Our closest living relatives share perfect identity with 96 percent of our DNA sequence.”
But assessing these claims is more challenging than it may appear. Note that the NIH report mentions 96 percent instead of 99 percent. Why? The same NIH report also includes the figure of 99 percent further on in its description, so none of the figures is an error. It turns out that the 99 percent figure arises by using a number of restrictions: (1) ignore repetitive portions, (2) compare only sequences that can be aligned naturally with one another, and (3) consider only base-pair substitutions, not “indels” (see below).
Comparisons of this kind get technical, because there can be several kinds of correspondence and noncorrespondence between DNA strands. Let us lay out briefly some of the issues. At the level of molecular structure, DNA contains a “code” composed of four “letters,” namely, ACGT (the letters stand for four distinct bases, adenine, cytosine, guanine, and thymine). The DNA code uses a particular sequence of letters, such as ATTGTTCTCGGC, to specify the exact sequence of amino acids that are to be used to construct a protein. Human DNA and chimp DNA align when one finds the same sequence of letters in both kinds of DNA:
A variation is called a “substitution” when there is a different letter at some one point in the sequence:
(The T does not match the G in the middle of the sequence.) A variation is called an “indel” (short for insertion/deletion) when one of the sequences has extra letters:
If the comparison focuses only on substitutions within aligned protein-coding regions, the match is 99 percent. Indels constitute roughly a 3 percent difference in addition to the one percent for substitutions, leading to the figure of 96 percent offered by the NIH.
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