Introduction

We have now seen that the earth is very old, and that the fossil record reveals organisms with increasing complexity gradually appearing through time. We can even draw lines of common descent and create trees showing the relatedness of organisms. In recent years, we have gained a new way to unlock the mysteries of God’s creation through reading the DNA sequences of organisms, what Francis Collins terms, “deciphering God’s instruction book.”1 DNA sequences reveal the relatedness of all species and confirm the lines of continuous descent shown in the fossil record. To see this, we first need a basic understanding of DNA.

DNA is a molecule that contains the instructions for life. This instruction book is written in an alphabet with just four letters—A, T, C, and G—which represent the four subunits, or bases, which make up the DNA chain. The DNA is then “read,” and proteins are created based on its instructions. A three-letter block of DNA is translated into one amino acid, the building block of a protein. As there are more three-letter combinations than there are amino acids, there are redundancies—for example, both GAA and GAG code for an amino acid called glutamic acid.

The stretches of DNA that code for a protein are called genes, but between genes are long stretches of DNA that do not code proteins. Some pieces of these non-coding regions play important regulatory roles (they help to turn DNA reading on or off), but the majority simply fills space. Mutations cause changes in the DNA sequence, and it is on these changes that selection acts. DNA takes on a two-stranded double helix shape, and many genes are packaged together in massive molecules called chromosomes. All the chromosomes for an organism taken together are said to be that organism’s genome.

Scientific and technological advances in the last two decades have allowed us to read the genomes of a great number of organisms, including ourselves. What has the genome revealed?

Continue: Large-scale Findings

Large-scale Findings

When we compare the genomes of different species, starting with a stretch of human DNA and determining the likelihood of finding that sequence in the other species, we get data like that shown in Table 1.2 This kind of data provides striking support for the theory of evolution.

Table 1

	Gene Sequence That Codes for Protein	Random DNA Segment Between Genes
Chimpanzee	100%	98%
Dog	99%	52%
Mouse	99%	40%
Chicken	75%	4%
Fruit fly	60%	~0%
Roundworm	35%	~0%

First, simply by comparing the relative similarities of different species, once can construct a tree of relatedness, totally independent of fossil or anatomical data. (For example, two species whose DNA is 95% alike will be closely related, but if their DNA is only 40% alike they will be more distantly related.) Amazingly, this tree is incredibly similar to other trees based on morphology and fossil data, and the trees are independently derived!3 We see how God reveals his truth to us from multiple vantage points.

Further, this data gives evidence for natural selection, a key mechanism of evolution. Natural selection means that creatures with better-adapted traits will survive to produce more offspring. From this, one would expect the coding regions (genes) to have fewer differences than non-coding regions. Why is this? Differences result from mutations, and most mutations are harmful, killing the creature before it can reproduce. This is particularly true in the gene regions that code for proteins necessary for survival. However, more mutations can persist in the non-coding DNA where they do not do as much damage. And this is exactly what the data shows—much higher similarity in the protein-coding regions than in the non-coding areas between genes. And the data is actually even stronger: w ithin the protein-coding genes, we even see more changes in the form of silent mutations—for example, GAA changes to GAG, but glutamic acid is still formed—that do not affect the protein sequence; again, just as expected.4

Continue: Small-scale Findings

Small-scale Findings

More interesting insights are revealed as we read out the “language of God” in closer details and see more clearly the interconnectedness of species.

If you compare the genomes of humans and mice, you find similar genes that are lined up in the same order.5 You also find interesting sequences called ancient repetitive elements (AREs).6 AREs come from “jumping genes,” stretches of DNA that are copied and inserted throughout the genome, and they are quite common (the human genome is thought to be made of ~45% AREs). Comparing the human and mouse genomes, one finds AREs also in the same approximate locations. This strongly suggests the relatedness of humans and mice. The simplest explanation is that the shared AREs were inserted in a common mammalian ancestor, and they stayed in position from then on. This is particularly compelling because one can find truncated AREs, damaged in the process of the move, that are also in the same positions.

Further evidence for common descent is found by comparing the DNA of humans and chimpanzees, which is found to be 96% identical.7 All human DNA is packaged into 23 pairs of chromosomes, while chimp DNA is contained in 24 pairs chromosomes. The chromosomes for humans and chimps can be lined up, showing a striking similarity in size and composition. However, it appears that human chromosome 2 was formed by the fusion of two chimp chromosomes (see figure).8 With current technology, we can now look at area of fusion on chromosome 2, and we find something astounding. There are characteristic sequences that are found almost exclusively at the ends of chromosomes. It is these sequences that are observed in the middle of chromosome 2 right where the fusion is believed to have taken place.9 This is stunning evidence that at some point in history, two chromosomes fused together in a human ancestor to form what would become our chromosome 2.

Continue: Conclusion

Conclusion

The text of DNA confirms the interrelatedness of species. It independently produces a matching tree of life to that of the fossil record, and the differences it reveals align with the predictions of evolutionary theory. Looking more closely, we can see remarkable evidence of common descent of humans with mice and chimpanzees through chromosome order, ancient repetitive elements, and confirmation of chromosome fusion. And these are just a tiny set of the data pointing to this conclusion – much more can be found looking at sequences known as pseudogenes, retroposons, and virus insertions10. All confirm the fossil record and point to descent from a common ancestor.

But is this data something to be frightened by? Does common descent remove God from the role of creator? Collins asserts “no”: “Freeing God from the burden of special acts of creation does not remove Him as the source of the things that make humanity special, and of the universe itself. It merely shows us something of how He operates.”11 Falk sees descent with modification as the enactment of God’s original creative command of “let”: “Let the waters swarm with swarms of living creatures,” “let birds fly above the earth across the expanse of the heavens,” and “let the earth bring forth creatures according to their kinds.” 12 As we understand more and more how the brilliant array of species on earth came to be, we glimpse more fully the glory of their Creator.

Next Page: Tying It Together