Pseudogenes:
Argument for Evolution and Against Design?By Rich Deem
Pseudogenes:
Argument for Evolution and Against Design?|
Pseudogenes are Bad Design? |
| It has been argued that the presence of apparently copied, non-functional DNA sequences (known as pseudogenes) support the theory of evolution and invalidate the idea that an intelligent Agent created life on earth. This article examines some of the ways in which pseudogenes do not support evolutionary theory and some of the underlying assumptions implicit in the argument that God would not design pseudogenes. |
Pseudogenes are regions of non-coding DNA (DNA that does not code for functional protein) that has been apparently duplicated from functional genes. Genes, and even chromosomes and entire genomes can be duplicated through copying errors. If evolution were true, it would be expected that some of these duplicated genes would undergo mutation that could render them useless. These pseudogenes would be passed down from generation to generation and across species as one species evolved into another. Random mutations would be expected to be inserted into the sequence, since there would be no selection pressure to eliminate less fit sequences. An examination of these pseudogenes among families related through descent would be expected to reveal a simple inheritance of these pseudogenes and the mutations that they would have accumulated over time.
Much has been made in the past of non-coding (does not code for messenger RNA, and therefore has no protein product) or "junk" DNA found in eukaryotes. To a large degree, these "non-useful" coding regions do not exist in the prokaryotes (bacteria). However, bacterial DNA is not enclosed in a nucleus, nor is it found in individual chromosomes (as in eukaryotes), but exists as just one long piece of DNA. At least nine classes of non-coding DNA are now recognized: introns, satellites, minisatellites, microsatellites, 3' untranslated regions, heterogeneous nuclear RNA, short interspersed elements, long interspersed elements, and pseudogenes. Pseudogenes are regions of DNA which resemble portions of coding genes from which they are hypothesized to have been derived. They themselves do not code for proteins, since they usually do not begin with a "start" coding sequence.
An article by Gary Gilbert published in the October, 1992 Spectrum magazine presented the beta globin pseudogene as compelling evidence for human's and ape's evolution from a common ancestor. Gilbert suggested pseudogenes, and other non-coding DNA, are molecular potsherds that can be used to reconstruct a species' evolutionary history, requiring that this DNA really have no function, but continues to be produced as a partial record of what once was an important adaptation. Many studies have been carried out regarding different pseudogenes. A study done by Gonzalez et al.1 looked at ribosomal DNA (rDNA) in chimpanzee, gorilla, orangutan, gibbon, and rhesus monkey rDNA. The 2-kb pseudogene was present in the apes but not in Old World monkeys. Some of the Alu elements of the gene were shared by all the primates studied, one was absent only from the rhesus monkey rDNA, and another was absent from both gibbon and rhesus rDNA. This kind of random inclusion of Alu elements does not support the simple evolutionary paradigm of common descent.
Another study by Minghetti and Dugaiczyk2 examined the enolase pseudogene, present in humans and four other primates, including the baboon, an Old World monkey. The accepted value of 5 x 10-9 nucleotide substitutions per site per year as the evolutionary rate for pseudogenes would lead one to conclude this pseudogene arose 14 million years ago. However, evolutionary theory states Old World monkeys diverged from the hominid lineage some 30 million years ago. It is difficult to explain how the sequence substitution rate would vary from one pseudogene to another, since they are non-coding, and therefore should not be subject to any form of natural selection.
What is common to all these pseudogene studies is that the pseudogenes from humans and apes are not identical. One would expect some similarity, since 98% of our genome is identical to that of chimpanzees. What is the purpose of this non-coding DNA? In humans, 97% of the genome is non-coding, suggesting that it must serve some purpose. Even evolution would not be expected to produce a species which has an efficiency of only 3%. Natural selection should have removed all this useless DNA. Much of the non-coding DNA that was once considered nonfunctional is actually highly functional. In fact, recent studies show that some of this non-coding DNA can control expression of other DNA, and other non-coding DNA probably serves to give structure to DNA and the chromosomes.
Does the presence of pseudogenes eliminate the possibility that God created life? To come to this conclusion, there are some assumptions that are implicit in the evolutionists' argument. The first assumption is that God would only create new creatures by producing an entirely new copy of DNA. In other words, DNA would be expected to be completely redesigned from any previously existing organism. Is this the way God works? We know from science that the Sun is a second generation star - formed from the remains of a supernova. For this reason, the Solar System is highly metal enriched, which is required for the existence of life on earth.3 Therefore, God does reuse material when designing "new" structures. When Jesus made wine at the marriage feast in Cana of Galilee (John 2:1-11), He did not begin with nothing or air, but began with water. Part of the water was changed into alcohol, but greater than 80% of the original water was unchanged. When God brings a person to salvation, He does not change the genetics or physical makeup of the individual. The person remains in the same body - often a body that has been ravaged by the effects of a lifetime of sinful behavior.
A good analogy in the design of a genetic code is the design of computer programs. I do a significant amount of computer programming as part of my job. When I write programs, I always reuse sections of code in the new programs. I do not begin by writing an entire program from scratch. This would be silly, and highly inefficient. The computer program consists of the GUI (graphical user interface) and the code that performs the actual computations. This is analogous to biological organisms. The GUI is the phenotype (the way the organism looks) and the code that performs the computations is the biochemical pathways. If one Designer created all biological organisms, we would expect to see similar genetic code for both phenotype and biochemical pathways. This is a good argument in favor of monotheism as opposed to polytheism.
The Bible says that God created humans from the dust of the earth.4 This statement suggests that humans were designed from preexisting material. I propose that part of this "dust" consists of the genetic code of previously existing organisms. If you were going to create a new species of primate, you would begin with primate DNA. This DNA would be altered to form the unique characteristics of the new species. I believe that this is the method that God used to create new species of life on earth. How does this differ from evolution driven through natural selection and how can you distinguish the two methods? Naturalistic evolution could, in theory, produce some of the changes in structures that would account for some of the phenotypic differences observed between the old and new species. However, evolution is unable to account for the design of new structures. Even more of a problem are the ravages of mutation on the genomes of organisms.5 Mutation, the mechanism by which evolutionary change is proposed to occur, most often has no effect upon the fitness of an organism. In humans, these "neutral" mutations occur at a rate of 2.6 mutations per person per generation. However, deleterious mutations occur at a rate of 1.6 mutations per person per generation. Although these deleterious mutations are usually recessive (not expressed unless there are two copies), they will accumulate in the gene pool over time. Decreases in population size leads to the expression of these deleterious mutations through inbreeding, which seriously affects the fitness of the species. In fact, this is the mechanism by which species go extinct. Because of the small amount of genetic variation among humans, evolutionists have proposed that the human species went through a population bottleneck in the recent past. However, such a bottleneck would lead to expression of deleterious mutations, which would further drive down the population numbers, leading to extinction. I believe that God created humans by editing primate DNA - adding new features and removing the deleterious mutations of this DNA template. If evolution were the mechanism by which species arose, deleterious mutations would continue to accumulate as new species evolved. This mechanism would lead to ever increasingly defective DNA through the biological history of the earth. How does this creationary model relate to pseudogenes? Since pseudogenes are not deleterious, I believe that God left them in the genome as part of the filler DNA required to maintain chromosome structure.
PSEUDOGENES AND ORIGINS (http://www.grisda.org/reports/or21_91-.htm) L. J. Gibson, Geoscience Research Institute (from Origins 21(2):91-108, 1994)
Last updated 10/23/01