Evolution and Mormonism: A Quest for Understandingby Trent D. Stephens, D. Jeffrey Meldrum, Forrest B. Peterson
Scientists discover more every day about how life developed on Earth. Details that stream in from the new field of molecular biology rival the ongoing findings of paleontologists as they fill in the missing pieces in the fossil record. Professors Stephens and Meldrum, aided by the perspective of a non-scientist, Forrest B. Peterson, review the data for a
Scientists discover more every day about how life developed on Earth. Details that stream in from the new field of molecular biology rival the ongoing findings of paleontologists as they fill in the missing pieces in the fossil record. Professors Stephens and Meldrum, aided by the perspective of a non-scientist, Forrest B. Peterson, review the data for a general Latter-day Saint audience.
Their approach comes from a position of faith. They quote from the Creation account in the Pearl of Great Price: ”And the Gods said: Let us prepare the waters to bring forth abundantly the moving creatures that have life. And the Gods saw that they would be obeyed and that their plan was good.” In the authors’ view, the passage’s emphasis on process over end result is consistent with modern science.
According to the LDS church, “Whether the mortal bodies of man evolved in natural processes to present perfection” or were formed by some other means is “not fully answered in the revealed word of God.” That God may have created the mechanism by which all life was formedrather than each organism separatelyis a concept that the authors find to be a satisfying and awe-inspiring possibility.
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DNA on the Witness Stand
One of the most basic issues dividing science and religion is the notion that our physical bodies are, or are not, related to the rest of nature. Many people believe that if we are the spirit children of God, then our physical bodies must be unique. They believe that if our bodies are in any way related to those of other animals, such a relationship is in some way degrading. We see a striking parallel between this belief and the medieval concept that if humans are the center of God’s creation then Earth must be the center of the universe. Even though this notion seems odd today, it was adamantly adhered to in previous generations (up to about 300 years ago). Eventually, the scientific data became so overwhelming that the notion of an Earth-centered universe had to be abandoned, even by religious leaders and the lay public. The idea that because we are at the center of God’s attention we should also be at the center of the physical universe was an error of logic which ultimately could not be supported by observation. But the discovery of our world’s true position in the universe does not negate God’s existence or diminish his love for each of us his children.
Likewise, the modern molecular data, which have accumulated over the past twenty-five years, overwhelmingly support the notion that we are genetically related to other animals and completely contradict the idea that we are genetically unique. As with an Earth-centered universe, the idea that because we are spirit children of God and are created in his image our physical bodies should be unique is an error that is not supported by the data. In fact, there are far more data supporting the concept that humans are related to other animals than to support the idea that Earth is not the center of the universe. As with the evidence that eventually led all people to accept the notion that Earth is not the center of the universe, the evidence that humans are biologically connected to other animals is overwhelming and cannot be dismissed. If humans were created by some means that made us unique (i.e., by “special creation”), then what is the basis of the demonstrable biological connection?
Some of the most powerful data supporting the theory of evolution in general and, specifically, the notion that all of nature, including humans, are related come from the relatively new field of molecular biology, the study of living things at the level of DNA and its associated molecules. DNA, or deoxyribonucleic acid, an acidic molecule within the cell nucleus which contains the sugar deoxyribose, is the genetic material of cells and is the template for protein synthesis. DNA provides the master pattern for the structure of all proteins (this is described in more detail below). In order to understand the magnitude of these molecular data, it is important to understand something about the field of molecular biology itself. Furthermore, in order to contrast our current level of knowledge in biology with that of even the very recent past, a brief overview of the history of molecular biology is necessary.
This chapter deals with these very issues. Many people may worry that they cannot understand molecular biology. However, it is important to realize that much of what is understood in modern biology about evolution requires a basic knowledge of the subject. We believe that some of the most elementary concepts of biochemistry and molecular biology can be readily grasped by the non-scientist.
We have designed or borrowed analogies which we believe will help readers understand some of the fundamental and important issues.
All living things are made up of cells, the basic functional units of life. It is important to know that the life of a single cell does not necessarily depend on its presence in the body. Cells can be removed from the body and kept alive for days, weeks, or even years.
Cells are very tiny. Approximately 10,000 of them could fit comfortably, in a single layer, on the head of a pin. As small as they are, each cell is a virtual microcosm of activity and contains millions of individual molecules, whose interactions are the basis of the cell’s function. Molecules are composed of atoms and range in size from 1/1000 to 1/200,000, the diameter of the cell. At the very heart of the cell, within the nucleus, is a group of relatively large molecules, the DNA, the master controls of the cell. Functional DNA is what distinguishes living things from non-living things. DNA is also the basis of inheritance of genetic information from one generation to the next.
The nucleus may be thought of as a library containing hundreds of books (the DNA) with information about the cell, including much of its structural and functional information, that will be passed on to the next generation. The books in this library also contain information about the history of the cell and about its relatedness to other cells in other animals. This recorded history has been stored in the cell’s library for thousands of generations, just waiting to be read and comprehended. Today, for the first time, those books are being opened and read at an incredible pace.
When Darwin published The Origin of Species in 1859, biologists knew nothing about DNA or the other molecules making up the cell. They knew very little about the cell itself. The “cell theory,” which states that all living things are made up of cells, was just emerging. Biologists of that time did not know how traits are inherited. Darwin realized that a major obstacle to his theory of natural selection was explaining how these are passed from one generation to the next.
The problem of inheritance was partly solved when the work of Gregor Mendel was discovered at the turn of the twentieth century. His work established the field of genetics but, at the same time, brought to light another mystery: What was the basis of the genetic code? What was a gene made of? What molecules were responsible for storing and transmitting the encoded information; what was the nature of the code itself? And, of critical importance to Darwin’s theory, can genes change?
One of the objectives of biology in the first half of the twentieth century was to “crack” the genetic code. By mid-century, it had been established that genes are made of DNA, but critical questions remained: what is the structure of DNA and how does it replicate? During the early 1950s, James Watson and Francis Crick were working from x-ray diffraction photographs taken by Maurice Wilkins and Rosalind Franklin. They deduced that DNA molecules form a double helix, referring to their shape which resembles a minute ladder twisted into a spiral. The discovery of this structure allowed Watson and Crick and others to establish how the genetic code works at the chemical level, thus “cracking” the elusive code and ushering in a whole new era for biology. The “molecular age” was born. For their discoveries, Crick, Watson, and Wilkins shared the 1962 Nobel Prize for “Physiology or Medicine.” (Sadly, Franklin had died of cancer before the prize was awarded, and did not share in the success her work had made possible.)
In 1965 Watson wrote a book entitled Molecular Biology of the Gene. This influential work outlined the new field of molecular biology. Before its publication, the term “molecular biology” was seldom used. By the time his book was published, the codes for a few small proteins had been deciphered, but few comparisons between the encoded sequences (similar to the order or sequence of letters making up words) for proteins had been made between species or classes of plants or animals. Furthermore, the techniques for rapidly sequencing DNA (discovering the sequence of the base units) were not developed until the early 1970s. Therefore, essentially all of what we know about animal interrelatedness at the molecular level has been discovered since 1970. It is important to remember that most of the books that have been written concerning the Mormon church and the theory of evolution were published before any of the molecular data, which are some of the most convincing supporting the theory of evolution, were available.
The first gene was isolated from a bacterium in the summer of 1970, and no genes had yet been sequenced. We have now sequenced thousands in hundreds of species of plants and animals. The entire DNA sequence is known for the bacterium E. coli, from which the first gene was isolated. The complete DNA sequence is also known for several other species. More rapid techniques are being developed all the time, such as the polymerase chain reaction (PCR) which has allowed us to produce millions of copies of a given stretch of DNA in a matter of hours. We have gone so far in the past quarter of a century that by the year 2003, less than thirty-three years after the first gene was sequenced, we will have sequenced the entire human genome (a genome is the entire complement of genes contained in every cell in the body), comprising approximately 80,000 genes in all. Every normal human has the same number of genes, but differ in the precise details of their DNA sequence. That is what makes each of us unique.
DNA is composed of basic building blocks called nucleotides. Only four types of nucleotides exist in DNA, represented by the letters A, G, C, and I. Early researchers thought that DNA, with an alphabet consisting of only four letters, was not sufficiently complex to store all the information needed by a living cell. However, with the advent of computers, we now recognize that even a binary code (consisting of only two numbers, 1 and 0) can store and transmit tremendous amounts of information.
The DNA alphabet spells out a code (codon) for particular amino acids. They combine to form proteins, which are in turn the building blocks and machinery of the body. A gene is a portion of DNA that codes for a particular protein product, something like a single word in a sentence or an ingredient in a recipe. Other sequences of DNA serve a regulatory function, controlling the expression of the recipe. (A gene, like the recipe in a book, may remain untranscribed. When it is transcribed and translated, like making a cake from a recipe, the process is called expression.) Also present are stretches of non-coding DNA, which may be thought of as blank spaces between the genes.
As cells continually grow and divide, the DNA library is replicated. During the process of copying millions of nucleotides every time a cell divides, errors are introduced into the new sequences. Such errors may simply be the substitution of a single nucleotide (say an A for a T), or the deletion of a portion of the sequence (e.g., the sequence ATACCGTT being reduced to ATACCG), or the duplication of a segment of DNA (e.g., the sequence ATAC becoming ATACATAC). These errors are called mutations. Most mutations are repaired by enzymes in the cell with that specific function; not all errors are repaired, however. Some occur within genes, whereas others occur in non-coding DNA and are inconsequential. Some occur in the cells of the body, which result in diseases such as cancer. When a mutation occurs in reproductive cells, it may be passed on to the offspring, making it different in some way from its parent. A mutation in a gene involved in the pathway for producing color may result in a person who does not produce skin and eye color. Most mutations reduce survivalbut some are beneficial to the organism in the face of changing conditions. For example, mutated insects can become resistant to pesticides, prompting the development of more powerful and more toxic chemicals. Mutations in bacteria may make them resistant to antibiotics. In fact, the overuse of antibiotics has precipitated the emergence of resistant bacteriaposing an international medical crisis.
Mutations that occur in the non-coding regions of DNA (in the blank spaces) have little or no effect on the individual or his or her offspring (i.e., such mutations do not change structure or function of the individual). However, the pattern of accumulated mutations within the non-coding regions results in a relatively unique identity in the DNA of each individual and his or her close relatives. To illustrate, imagine yourself in a shooting gallery. There are targets and blank spaces between the targets. When a bullet hits a target, the target falls over, but if the bullet misses and strikes the space in between, nothing happens. However, the pattern of hits in the space between the targets leaves a unique record of the shots fired. The back walls of no two shooting galleries are exactly alike. In the same way, mutations that “hit” genes can directly affect the individual or his or her offspring; but in the non-coding regions between genes, or “targets,” they have no effect on the individual. Still, the “hits” in the non-coding regions, the “spaces between the targets,” are recorded, with no two individuals having exactly the same pattern. The pattern of hits in the non-coding regions is passed on to the offspring, providing a unique record of the offspring’s heritage.
The discovery that DNA sequences are unique among individuals and families has led to the development of a technique for identification. This technique, called DNA fingerprinting, permits a profile of key “landmarks” to be compared between samples. The procedure takes advantage of the fact that many cells are equipped with a defense mechanism to protect against invasion by foreign DNA. This defense consists of proteins, called restriction enzymes, that recognize specific short sequences of DNA, attach to those sites, and snip the invading foreign strand into two. By exposing a sample of DNA to a select battery of restriction enzymes, the strand will be snipped into a collection of variable-length fragments. The resulting fragments are applied to an electrophoresis gel and the electrical current causes the fragments to spread along the gel, the shorter fragments moving farther than the longer ones. Once this gel is labeled with a dye, it produces a characteristic “fingerprint” of the individual, a relatively unique banding pattern produced by the restriction fragments.
The use of DNA fingerprint evidence has become an important forensic tool in criminal investigation. DNA samples collected from a crime scene can be used to virtually establish the presence or absence of a suspect at the scene. Such evidence is also employed to settle questions of paternity, as in the cases of infants switched at birth in a hospital.
Questions of family relatedness can also be determined. Recently, the DNA of an unknown Vietnam soldier in Arlington National Cemetery was tested and compared to blood samples of presumed family members, the dead soldier was identified, and his remains were returned to his family. As a result of this case, the Pentagon plans to take DNA samples from every soldier to create a registry. This future registry will make it nearly impossible for there ever again to be an unknown soldier.
Similarly, when nine skeletons were found in a shallow grave in July 1991, it was possible to identify the remains of the tsar, his wife, three of their five children, the royal physician, and three servants. Even though the cells had been dead for seventy-five years, DNA fragments were still intact. Analysis revealed an exact match between the wife, the three children, and a living maternal relative. Similar results were achieved with the remains of the former tsar and two living maternal relatives. This forensic evidence supported the hypothesis that the remains were those of the executed Romanov family. On the other hand, DNA analysis refuted the claim of a woman who had claimed to be the surviving Anastasia Romanov.
Similar techniques are currently being used to identify family relations among the ancient pharaohs, who lived 5,000 years ago. DNA has been extracted from 10,000-year-old human bones and teeth, and from 135 million-year-old amber-imbedded insects. DNA from Neandertal fossils, 30,000-100,000 years old, has also been sequenced. The data from this study suggest that Neandertals, although human-like in appearance, were not direct ancestors of modern humans (see Krings, “Neandertal DNA sequences,” 19-30).
This new science has taken the witness stand in cases of homicide, paternity, and issues of family relatedness. DNA fingerprinting can identify an individual and tie him or her to living or dead relatives. These same techniques are used by biologists to investigate the interrelatedness of various species. For example, a controversy has existed among botanists for most of this century as to whether yews, which have flat needles and berry-like fruit, should be classified with conifers, which are needle-bearing evergreens with typical cones, or whether they should be classified as a separate class or even as a separate phylum. Until recently, this controversy was unresolvable. However, molecular data collected within the past ten years clearly indicate that yews, for all their apparent morphological differences, are closely related to the other conifers (see Li,Molecular Evolution, 160-63).
What do the molecular data reveal about humans’ closest relatives in the animal kingdom? The question of which, if any, African apes share a common ancestor with humans has also been investigated using DNA sequencing. Mounting evidence indicates that humans and chimpanzees are the most closely related (see Bailey, “Hominoid trichotomy,” 100-108). These findings have independently borne out the conclusions of earlier comparative anatomists that humans are more closely related to the chimp and gorilla than either the chimp or gorilla are related to the third great ape, the orangutan. When the DNA sequences of two humans selected at random are compared, they may differ on average by as much as one out of every 200 nucleotides. In other words, they are about 99.5 percent similar. If the DNA sequences of a human and a chimpanzee are compared, 1.45 out of every 100 nucleotides are found to be differentabout 98.5 percent similar. Human DNA is 97 percent similar to that of orangutans and 92.5 percent similar to that of rhesus monkeys. Likewise, chimpanzees are only 92.5 percent similar to rhesus monkeys but 97 percent similar to orangutans. Animals that are more distantly related have even greater DNA sequence differences.
These differences can be seen not only in the DNA but in proteins as well. Proteins are made from the DNA template by a process which we will describe later in this chapter. Because of this relationship, amino acid (amino acids, incidentally, are carbon-containing acids that have an amine group [NH2] and a “side group,” which ranges from a single hydrogen atom to larger, more complex groups of atoms) sequences in proteins can be used for comparisons across species. We can compare, for example, the human protein cytochrome camino acid sequence to that of any other plant or animal. We find that all 100 amino acids in human cytochrome c are identical to those of the chimpanzee, 99 percent are identical to those of monkeys, 90 percent to those of a dog, 88 percent to a horse, 85 percent to a chicken, 83 percent to a snake, 82 percent to a frog, 79 percent to a fish, 72 percent to a fly, 57 percent to wheat, and 52 percent to yeast. The list goes on, confirming the validity of the hypothesis that more closely related plants and animals have more closely related amino acid sequences and that more distantly related plants and animals have less similar sequences. Even though there are up to 50 percent differences in amino acid sequences in cytochrome c, the cytochromes from one plant or animal can substitute for those of another. (See, for example, Ernst, “Substitutions of proline 76,” 13,225-36; and Tanaka, “Amino acid replacement studies,” 477-80.)
When he wrote The Origin, Darwin did not know the basis of inherited variation. He knew nothing about DNA, cytochrome c, or amino acid sequences. Nonetheless, the theory of descent by natural selection predicted in 1859 the relationship in DNA and amino acid sequences that we observe today. No more powerful evidence exists for any scientific theory than that it clearly and precisely predicts the data obtained from future experiments and observations, especially in fields of science that do not yet exist.
The use of DNA data in forensic science and questions of animal interrelatedness have only become possible in the past three decades and, on a larger scale, only within the past ten years. However, in spite of the relative youth of the molecular biology field, the data which have accumulated are:
(1) Massive. There are literally thousands of volumes of DNA sequences now available. It is also equally important to know that the human genome contains huge regions of non-coding DNA. The sequence similarities and differences in these non-coding regions provide the most powerful information about relatedness among humans (such as in homicide and paternity cases) and between humans and other animals.
(2) Rapidly accumulating. Newer and faster sequencing techniques are being developed all the time, cutting by factors of hundreds or thousands the time required to sequence a gene compared to the early days of sequencing. Several new genes are being sequenced every day. By the year 2003, the entire human genome, consisting of approximately 80,000 genes will be sequenced, and large portions of the genomes of other plants and animals will be known. The entire DNA sequences of several viruses, bacteria, and yeast are already completely known.
(3) Consistent. The DNA sequences discovered for similar genes in different plants and animals have been found to be remarkably alike, demonstrating that there is an impressive similarity in structure and function at the molecular level.
(4) Supportive of the concept of relatedness. When we examine DNA sequences to determine how closely or distantly two plant or animal species are related, it is not the conserved (similar) portion of the DNA sequence that is important; rather it is the portion of the sequence that is different (variable, often non-coding regions) that matters most. In every organism studied to date, there is a remarkable correlation between the amount of similarity in those variable regions of DNA and the proposed relationship between the plants or animals examined. The differences between sequences apparently reflect the accumulation of mutations in separate biological lineages derived from a common ancestor. It is important to emphasize, once more, that this information, which is the most powerful information available for examining questions of interrelatedness between living things, was not available twenty-five years ago. This same type of information is used in courts of law to determine DNA matches in paternity or homicide cases. Some people readily accept DNA data as evidence for relatedness among humans yet reject the same data indicating our relatedness to other animals.
These data powerfully support the theory of evolution and its prediction that closely related species exhibit closely related DNA sequences. Because of the consistency of these data, we can confidently predict that anyone reading this book can go to any college or university library, pick up any scientific journal containing published DNA sequences, and verify the relatedness of the species presented. These data are powerful because they directly address the forces of creation, the motive cause that forms each plant and animal. They are also powerful because they are objective and do not depend on the subjective comparisons of early systematics.
We present here a demonstration you can try yourself, which is an analogy of the relatedness of DNA sequences among species. All you need for this demonstration are four different colors of paper clips, about thirty of each. From a mixed box with all four colors, select ten paper clips at random and link them together to form a chain. This chain will be made up of the four colors of paper clips in random order. Lay this chain of ten paper clips onto a table so that you can see the pattern.
Now construct a second chain of ten paper clips that is identical to the first. After this second chain is constructed, pick one additional paper clip at random from the box of assorted colors. Then pick at random one link in the second chain. This may best be done by laying out the chain, closing your eyes, and pointing to one link. Once that link has been identified, replace it with the new link you selected from the box. There is a 25 percent chance that the link you are replacing will be the same color as the new link.
Now construct a third chain identical to the second and repeat the process of replacing one link. Once more the link and color of the replacement will be random. There is a 10 percent chance of replacing the same link and a 25 percent chance of replacing the same color as was there before. That does not matter; go ahead and complete the exercise. Repeat this process until you have a total of ten chains of ten paper clips each, with slight color variations. Once all ten chains are formed, place them into a box or some other container, and mix them up. Now dump out the ten paperclip chains onto a table and sort them out by degree of similarity (it works better if one person makes the chains and another person sorts them out). Organize the chains according to some order that you decide upon. How did you organize the chains? What was the basis of your decision to organize them the way you did? What are the implications of the organization you chose? There may be some chains that are identical and cannot be distinguished. What factors might result in identical chains?
The results of this demonstration are similar to what molecular biologists obtain in examining DNA sequences. We can consider these data relative to at least two alternative hypotheses: (1) The theory of evolution predicts that species are related to each other by descent; or (2) each species was created independently and uniquely, and therefore the species are not related. The DNA sequence data powerfully and consistently support the theory of evolution by indicating that species are related and just as powerfully and consistently refute the hypothesis of special creation. If each species was created independently and uniquely, and the species are not related, then some reasonable explanation must be advanced to explain the apparent relationship in DNA sequences. Science does not preclude the advancement of such an alternative hypothesis; rather, alternative hypotheses are encouraged. There is no conspiracy in science to suppress reasonable alternative hypotheses. The fact is, no reasonable alternative hypothesis has yet been proposed.
The DNA sequence data do not disprove creation, they simply help us explore possible mechanisms and patterns in the course of evolution. One of the most beautiful parts of God’s creation is the elegantly simple DNA molecule. That graceful spiral contains the possibility for storing almost infinite amounts of information. DNA is copied and transferred from one generation to the next with almost perfect fidelity. Hence, in the short term, likes beget likes. The “almost” part of the process of DNA replication allows for the variation that is a critical part of the creative process. Variation permits species to adapt in the face of a changing environment. That variation is certainly one of God’s most profound laws.
Some people argue that it comes as no surprise that the “blueprints” for similarly appearing organisms are likewise similar. That would be a fair assertion if the DNA of an organism was anything like an architect’s blueprint, but such is not the case. Rather than a blueprint, an organism’s complement of DNA is more like a “recipe” in a scrapbook of family history. In addition to the instructions for the unfolding development of the organism, there are bits and pieces, souvenirs and memorabilia, from far-flung predecessors. Stretches of non-coding DNA-interons, tandem repeats, satellite DNA-have little or no effect on the outcome of development. Mutations accumulate in these stretches of DNA that are invisible to natural selection and therefore provide a relatively unskewed evolutionary record of the lineage like the pattern of bullet holes on the wall of the shooting gallery. When examined in conjunction with more conservative genes that code for functional proteins, these provide a means for determining which organisms share a most recent common ancestor.
The information contained in DNA may be compared to a cake recipe. Suppose you want to bake a very special cake using a recipe available in only a very limited number of cook books. Suppose, also, that the only cook book you can find containing the recipe is in the reference section of the local library and cannot be checked out. The recipe book could be thought of as the DNA sequence for a given plant or animal and the cake recipe itself would be the DNA sequence of a gene for a given protein. The library can be thought of as the nucleus of a cell within the plant or animal. Just like a reference book, which cannot be removed from the library, DNA is too large a molecule to leave the nucleus.
If you want a copy of the cake recipe, your only choice is to copy it from the recipe book. You may choose to copy it onto a card, which you can then take home and use to make the cake. You transcribe the recipe from the recipe book onto the card. In the nucleus of an actual cell, a given stretch of DNA is transcribed as a sequence of ribonucleic acid (RNA), a molecule closely related to DNA. The RNA used to transcribe information from DNA that will be used to make proteins is called messenger RNA (mRNA). You may not choose to copy the recipe exactly as written in the book, but may choose to abridge some passages. For example, the recipe may state, “Add one cup of sifted all purpose flour.” You may write on your card, “Add one cup of flour.” In molecular terminology, the phrase that you transcribed is called an exon. An exon is the part of the DNA actually used to make a protein. That portion of the recipe you did not copy, “sifted all purpose,” is called the intron. An intron is the portion of a given DNA sequence not used to make the protein.
Once you have transcribed the recipe onto a card, you are ready to leave the library and go to your kitchen. You place the card on your kitchen counter or table, which may be thought of as the ribosome of the cell, where proteins are assembled. You then gather up all the ingredients for the cake and place them onto the counter. These are the amino acids from which the protein is to be made. You put the ingredients together according to the instructions in the recipe. Because you are now changing from a written recipe to a cake, the process is called translation. In molecular biology, translation is the process of making proteins from an mRNA template. The cake recipe provides the information for whether this will be a chocolate or lemon cake. Likewise, the DNA and mRNA sequences provide the information for the amino acid sequence in a given protein, and this sequence determines the structure and function of it.
Now let us consider changing the letters of the recipe, much like we did the paper clips in the previous demonstration. The original recipe states:
Add one cup of sifted all purpose flour.
The italicized words are the intron. Now change one letter, as though a typo had occurred in the recipe book:
Add one cup of sifted all purpose flour.
This change in the exon is referred to as a functional mutation, which makes the recipe nonfunctional as it can no longer be read correctly. Mutations occur randomly in nature, much like in the exercise of randomly replacing colored paper clips in a chain. Plants or animals with functional mutations rarely survive because the mutation tends to destroy some critical function. However, let us consider a change in the intron:
Add one pup of sifted all purpose flour.
In this case, the functional meaning of the recipe is not changed. This type of mutation is called a neutral mutation because function is retained. Neutral mutations can continue to accumulate (in nature, they accumulate at measurable rates). Let us say that the cook book goes through several editions without the accumulated errors being corrected. The page containing the publication date is lost from each book and you want to reconstruct the publication order of five editions of the book. Here is the phrase from each of the five editions:
Add one cup of sifted all pompose flour.
Add one cup of sufter all pompose flour.
Add one cup of sifted all porpose flour.
Add one cup of sufted all pompose flour.
Add one cup of sifted all purpose flour.
Assuming that no errors were corrected from edition to edition, which phrase came from the oldest, original cook book? Which came from the second edition, which from the third, fourth, and fifth? What is the basis of your conclusions?
Biologists use the same logic to determine not only relationships between plants or animals but also to determine the order of descent. Data obtained from such observations strongly agree with similar data obtained from other sources, such as the fossil record. All of the data combine to powerfully support the theory that all plants and animals are related by descent with modification from common ancestors.
The “witnesses” have testified; the evidence has been presented; the merits of the case rest upon the accumulated data. The fingerprint of our common biological heritage with animals appears self-evident. The same techniques employed in courts of law to settle disputes of paternity, or to research the history of genetic diseases in family genealogies, demonstrate our close relations to the rest of nature. Their validity as tools to elucidate genealogical relationships is unquestioned; why would their application to elucidate relationships between animal species be disputed?
We believe that these data provide insights into the processes used by God to create the plants and animals on this earth, including our own bodies. We must remember again that in science there is always the opportunity for alternative hypotheses to be advanced which better explain the observed data. However, in nearly 150 years of exhaustive study, no one has advanced a testable alternative hypothesis to explain the data that even begins to demonstrate the predictive power of evolutionary biology.
Meet the Author
Trent D. Stephens (B.S., Brigham Young University; Ph.D., University of Pennsylvania) is Professor of Anatomy and Embryology at Idaho State University, where he was named Distinguished Teacher in 1992 and Outstanding Researcher in 2000. He is the co-author of ten textbooks. He currently serves as bishop of the Pocatello Century Ward.
D. Jeffrey Meldrum (B.S., BYU; Ph.D., State University of New York) is Associate Professor of Anatomy and Anthropology at Idaho State University and Affiliate Curator of Vertebrate Paleontology at the Idaho Museum of Natural History. He is co-editor of a series of books on paleontology. He serves as a scout master in the Pocatello Fourth Ward.
Duane E. Jeffery (B.S., Utah State University; Ph.D., UC Berkeley) is Professor of Zoology at BYU. He has published in such professional journals as Genetics and the Journal of Heredity, as well as in the Proceedings of the National Academy of Sciences. He is a contributor to Science and Religion and The Search for Harmony.
Forrest B. Peterson is an award-winning writer and movie producer. In 1990 his Trouble in Oz won five Crystal Reel prizes from the Florida Film Festival. His church duties have included elders quorum president and gospel doctrine teacher.
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