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Apologetics Press :: Sensible Science

Do Human and Chimpanzee DNA Indicate an Evolutionary Relationship?
by Brad Harrub, Ph.D. and Bert Thompson, Ph.D.

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The collision occurred without warning. Prior to the impact, thoughts had revolved around dinner plans. Images of fried chicken and mashed potatoes, however, now have been replaced by an ear-piercing siren and flashing strobe lights, that dance off of street signs and store windows. Following the injured person’s six-minute ambulance ride, emergency room doctors assess the situation. There is extensive internal damage, and several organs are beginning to shut down. The prognosis is dim—unless a healthy kidney and liver are transplanted within the next 12 hours. A call is made to the National Organ Donor Registry, and the gravity of the situation is relayed to several donor officials. Within a matter of hours, a chartered air ambulance delivers the organs in a bright red Igloo™ cooler. As the anesthesiologist begins the necessary preparations for surgery, the patient notices the surgeon walk over and inspect the donated organs. The last words the patient hears as he drifts off to sleep is the surgeon saying, “Well, I guess chimp organs will have to do; after all, we share over 98% of the same genetic material.”

While many evolutionists proclaim that human DNA is 98% identical to chimpanzee DNA, few would lie by idly and allow themselves to receive a transplant using chimpanzee organs. As a matter of fact, American doctors tried using chimp organs in the 1960s, but in all cases the organs were totally unsuitable. 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 (Britten, 2002).

In 1962, James Dewey Watson and Francis Harry Compton Crick received the Nobel Prize in physiology or medicine for their discovery concerning the molecular structure of DNA. Just nine years earlier, in 1953, these two scientists had proposed the double helical structure of DNA—the genetic material responsible for life. By demonstrating the molecular arrangement of four nucleotide base acids (adenine, guanine, cytosine, and thymidine—usually designated as A,G,C, and T) and how they combine, Watson and Crick opened the door for determining the genetic makeup of humans and animals. The field of molecular biology became invigorated with scientists who wanted to compare the proteins and nucleic acids of one species with those of another. Just thirteen short years after Watson and Crick received their famed Nobel Prize, the declaration was made “that the average human polypeptide is more than 99 percent identical to its chimpanzee counterpart” (King and Wilson, 1975, pp. 114-115). This genetic similarity in the proteins and nucleic acids, however, left a great paradox—why do we not look or act like chimpanzees if our genetic material is so similar? King and Wilson recognized the legitimacy of this quandary when they remarked: “The molecular similarity between chimpanzees and humans is extraordinary because they differ far more than many other sibling species in anatomy and life” (p. 113). Nevertheless, the results were exactly what evolutionists were looking for, and as such, the claim has reverberated through the halls of science for decades as evidence that humans evolved from an ape-like ancestor.

One year following Watson and Crick’s Nobel ceremony, chemist Emile Zuckerkandl observed that the protein sequence of hemoglobin in humans and the gorilla differed by only 1 out of 287 amino acids. Zuckerkandl noted: “From the point of view of hemoglobin structure, it appears that the gorilla is just an abnormal human, or man an abnormal gorilla, and the two species form actually one continuous population” (1963, p. 247). The molecular and genetic evidence only strengthened the evolutionary foundation for those who testified of our alleged primate ancestors. Professor of physiology Jared Diamond even titled one of his books The Third Chimpanzee, thereby viewing the human species as just another big mammal. From all appearances, it seemed that evolutionists had won a battle—humans were more than 98% identical to chimpanzees. However, after spending a lifetime looking for evidence of evolution within molecular structures, biochemist Christian Schwabe was forced to admit:

Molecular evolution is about to be accepted as a method superior to paleontology for the discovery of evolutionary relationships. As a molecular evolutionist, I should be elated. Instead it seems disconcerting that many exceptions exist to the orderly progression of species as determined by molecular homologies; so many in fact that I think the exception, the quirks, may carry the more important message (1986, p. 280, emp. added).

In 2003, the completed human genome study is scheduled to be published. Before this massive project was created, scientists estimated that humans possessed 90,000 to 100,000 genes (a gene is a section of DNA that is a basic unit of heredity, while the genome constitutes the total genetic composition of an organism). With preliminary data from the genome project now in hand, scientists believe that the actual number of genes is around 70,000 (Shouse, 2002, 295:1447). It appears that only about 1.5% of the human genome consists of genes, which code for proteins. These genes are clustered in small regions that contain sizable amounts of “non-coding” DNA (frequently referred to as “junk DNA”) between the clusters. The function of these non-coding regions is only now being determined. These findings indicate that even if all of the human genes were different from those of a chimpanzee, the DNA still could be 98.5 percent similar if the “junk” DNA of humans and chimpanzees were identical.

Jonathan Marks, (department of anthropology, University of California, Berkeley) has pointed out the often-overlooked problem with this “similarity” line of thinking.

Because DNA is a linear array of those four bases—A,G,C, and T—only four possibilities exist at any specific point in a DNA sequence. The laws of chance tell us that two random sequences from species that have no ancestry in common will match at about one in every four sites. Thus even two unrelated DNA sequences will be 25 percent identical, not 0 percent identical (2000, p. B-7).

Therefore a human and any earthly DNA-based life form must be at least 25% identical. Would it be correct, then, to state that daffodils are “one-quarter human”? The idea that a flower is one-quarter human is neither profound nor enlightening; it is outlandishly ridiculous! There is hardly any biological comparison that could be conducted that would make daffodils human—except perhaps DNA. Marks went on to concede:

Moreover, the genetic comparison is misleading because it ignores qualitative differences among genomes.... Thus, even among such close relatives as human and chimpanzee, we find that the chimp’s genome is estimated to be about 10 percent larger than the human’s; that one human chromosome contains a fusion of two small chimpanzee chromosomes; and that the tips of each chimpanzee chromosome contain a DNA sequence that is not present in humans (B-7, emp. added).

The truth is, if we consider the absolute amount of genetic material when comparing primates and humans, the 1-2% difference in DNA represents approximately 80 million different nucleotides (compared to the 3-4 billion nucleotides that make up the entire human genome). To help make this number understandable, consider the fact that if evolutionists had to pay you one penny for every nucleotide in that 1-2% difference between the human and the chimp, you would walk away with $800,000. Given those proportions, 1-2% does not appear so small, does it?

CHROMOSOMAL COUNTS

It would make sense that, if humans and chimpanzees were genetically identical, then the manner in which they store DNA also would be similar. Yet it is not. DNA, the fundamental blueprint of life, is tightly compacted into chromosomes. All cells that possess a nucleus contain a specific number of chromosomes. Common sense would seem to necessitate that organisms that share a common ancestry would possess the same number of chromosomes. However, chromosome numbers in living organisms vary from 308 in the black mulberry (Morus nigra) to six in animals such as the mosquito (Culex pipiens) or nematode worm (Caenorhabditis elegans) [see Sinnot, et al., 1958]. Additionally, complexity does not appear to affect the chromosomal number. The radiolaria (a simple protozoon) has over 800, while humans possess 46. Chimpanzees, on the other hand, have 48 chromosomes. A strict comparison of chromosome numbers would indicate that we are more closely related to the Chinese muntjac (a small deer found in Taiwan’s mountainous regions), which also has 46 chromosomes.

This hurdle of differing numbers of chromosomes may appear trivial, but we must remember that chromosomes contain genes, which themselves are composed of DNA spirals. If the blueprint of DNA locked inside the chromosomes codes for only 46 chromosomes, then how can evolution account for the loss of two entire chromosomes? The task of DNA is to continually reproduce itself. If we infer that this change in chromosome number occurred through evolution, then we are asserting that the DNA locked in the original number of chromosomes did not do its job correctly or efficiently. Considering that each chromosome carries a number of genes, losing chromosomes does not make sense physiologically, and probably would prove deadly for new species. No respectable biologist would suggest that by removing one (or more) chromosomes, a new species likely would be produced. To remove even one chromosome would potentially remove the DNA codes for millions of vital body factors. Eldon Gardner summed it up as follows: “Chromosome number is probably more constant, however, than any other single morphological characteristic that is available for species identification” (1968, p. 211). To put it another way, humans always have had 46 chromosomes, whereas chimps always have had 48.

REAL GENOMIC DIFFERENCES

One of the downfalls of previous molecular genetic studies has been the limit at which chimpanzees and humans could be compared accurately. Scientists often would use only 30 or 40 known proteins or nucleic acid sequences, and then from those extrapolate their results for the entire genome. Today, however, we have the majority of the human genome sequences, practically all of which have been released and made public. This allows scientists to compare every single nucleotide base pair between humans and primates—something that was not possible prior to the human genome project. In January 2002, a study was published in which scientists had constructed and analyzed a first-generation human chimpanzee comparative genomic map. This study compared the alignments of 77,461 chimpanzee bacterial artificial chromosome (BAC) end sequences to human genomic sequences. Fujiyama and colleagues “detected candidate positions, including two clusters on human chromosome 21, that suggest large, nonrandom regions of differences between the two genomes” (2002, 295:131). In other words, the comparison revealed some “large” differences between the genomes of chimps and humans.

Amazingly, the authors found that only 48.6% of the whole human genome matched chimpanzee nucleotide sequences. [Only 4.8% of the human Y chromosome could be matched to chimpanzee sequences.] This study compared the alignments of 77,461 chimpanzee sequences to human genomic sequences obtained from public databases. Of these, 36,940 end sequences were unable to be mapped to the human genome (295:131). Almost 15,000 of those sequences that did not match human sequences were speculated to “correspond to unsequenced human regions or are from chimpanzee regions that have diverged substantially from humans or did not match for other unknown reasons” (295:132). While the authors noted that the quality and usefulness of the map should “increasingly improve as the finishing of the human genome sequence proceeds” (295:134), the data already support what creationists have said for years—the 98-99% figure representing DNA similarity is grossly misleading, as revealed in a study carried out by Roy Britten of the California Institute of Technology (see Britten, 2002).

Exactly how misleading came to light in an article—“Jumbled DNA Separates Chimps and Humans”—published in the October 25, 2002 issue of Science. The first three sentences of the article, written by Elizabeth Pennisi (a staff writer for Science), represented a “that was then, this is now” type of admission of defeat. She wrote:

For almost 30 years, researchers have asserted that the DNA of humans and chimps is at least 98.5% identical. Now research reported here last week at the American Society for Human Genetics meeting suggests that the two primate genomes might not be quite as similar after all. A closer look has uncovered nips and tucks of homologous sections of DNA that weren’t noticed in previous studies (298:719, emp. added).

Genomicists Kelly Frazer and David Cox of Perlegen Sciences in Mountain View, California, along with geneticists Evan Eichler and Devin Locke of Case Western University in Cleveland, Ohio, compared human and chimp DNA, and discovered a wide range of insertions and deletions (anywhere from between 200 bases to 10,000 bases). Cox commented: “The implications could be profound, because such genetic hiccups could disable entire genes, possibly explaining why our closest cousin seems so distant” (as quoted in Pennisi, 298:721).

Britten analyzed chimp and human genomes with a customized computer program. To quote Pennisi’s article:

He compared 779,000 bases of chimp DNA with the sequences of the human genome, both found in the public repository GenBank. Single-base changes accounted for 1.4% of the differences between the human and chimp genomes, and insertions and deletions accounted for an additional 3.4%, he reported in the 15 October [2002] Proceedings of the National Academy of Sciences. Locke’s and Frazer’s groups didn’t commit to any new estimates of the similarity between the species, but both agree that the previously accepted 98.5% mark is too high (298:721, emp. added).

While Locke’s and Frazer’s team was unwilling to commit to any new estimate of the similarity between chimps and humans, Britten was not. In fact, he titled his article in the October 15, 2002 Proceedings of the National Academy of Sciences, “Divergence between Samples of Chimpanzee and Human DNA Sequences is 5%” (Britten, 99:13633-13635). In the abstract accompanying the article, he wrote: “The conclusion is that the old saw that we share 98.5% of our DNA sequence with chimpanzee is probably in error. For this sample, a better estimate would be that 95% of the base pairs are exactly shared between chimpanzee and human DNA” (99:13633, emp. added). The news service at NewScientist.com reported the event as follows:

It has long been held that we share 98.5 per cent of our genetic material with our closest relatives. That now appears to be wrong. In fact, we share less than 95 per cent of our genetic material, a three-fold increase in the variation between us and chimps.

The new value came to light when Roy Britten of the California Institute of Technology became suspicious about the 98.5 per cent figure. Ironically, that number was originally derived from a technique that Britten himself developed decades ago at Caltech with colleague Dave Kohne. By measuring the temperature at which matching DNA of two species comes apart, you can work out how different they are.

But the technique only picks up a particular type of variation, called a single base substitution. These occur whenever a single “letter” differs in corresponding strands of DNA from the two species.

But there are two other major types of variation that the previous analyses ignored. “Insertions” occur whenever a whole section of DNA appears in one species but not in the corresponding strand of the other. Likewise, “deletions” mean that a piece of DNA is missing from one species.

Together, they are termed “indels,” and Britten seized his chance to evaluate the true variation between the two species when stretches of chimp DNA were recently published on the internet by teams from the Baylor College of Medicine in Houston, Texas, and from the University of Oklahoma.

When Britten compared five stretches of chimp DNA with the corresponding pieces of human DNA, he found that single base substitutions accounted for a difference of 1.4 per cent, very close to the expected figure.

But he also found that the DNA of both species was littered with indels. His comparisons revealed that they add around another 4.0 per cent to the genetic differences (see Coghlan, 2002, emp. added).

It seems that, as time passes and scientific studies increase, humans appear to be less like chimps after all. In a separate study, Barbulescu and colleagues also uncovered another major difference in the genomes of primates and humans. In their article “A HERV-K Provirus in Chimpanzees, Bonobos, and Gorillas, but not Humans,” the authors wrote: “These observations provide very strong evidence that, for some fraction of the genome, chimpanzees, bonobos, and gorillas are more closely related to each other than they are to humans” (2001, 11:779, emp. added). The data from these results go squarely against what evolutionists have contended for decades—that chimpanzees are closer genetically to humans than they are to gorillas. Another study using interspecies representational difference analysis (RDA) between humans and gorillas revealed gorilla-specific DNA sequences (Toder, et al., 2001)—that is, gorillas possess sequences of DNA that are not found in humans. The authors of this study suggested that sequences found in gorillas but not humans “could represent either ancient sequences that got lost in other species, such as human and orang-utan, or, more likely, recent sequences which evolved or originated specifically in the gorilla genome” (9:431).

The differences between chimpanzees and humans are not limited to genomic variances. In 1998, a structural difference between the cell surfaces of humans and apes was detected. After studying tissues and blood samples from the great apes, and sixty humans from various ethnic groups, Muchmore and colleagues discovered that human cells are missing a particular form of sialic acid (a type of sugar) found in all other mammals (1998, 107[2]:187). This sialic acid molecule is found on the surface of every cell in the body, and is thought to carry out multiple cellular tasks. This seemingly “miniscule” difference can have far-reaching effects, and might explain why surgeons were unable to transplant chimp organs into humans in the 1960s. With this in mind, we never should declare, with a simple wave of the hand, “chimps are almost identical to us” simply because of a large genetic overlap.

CONCLUSION

Homology (or similarity) does not prove common ancestry. The entire genome of the tiny nematode (Caenorhabditis elegans) also has been sequenced as a tangential study to the human genome project. Of the 5,000 best-known human genes, 75% have matches in the worm (see “A Tiny Worm Challenges Evolution”). Does this mean that we are 75% identical to a nematode worm? Just because living creatures share some genes with humans does not mean there is a linear ancestry. Biologist John Randall admitted this when he wrote:

The older textbooks on evolution make much of the idea of homology, pointing out the obvious resemblances between the skeletons of the limbs of different animals. Thus the “pentadactyl” [five bone—BH/BT] limb pattern is found in the arm of a man, the wing of a bird, and flipper of a whale—and this is held to indicate their common origin. Now if these various structures were transmitted by the same gene couples, varied from time to time by mutations and acted upon by environmental selection, the theory would make good sense. Unfortunately this is not the case. Homologous organs are now known to be produced by totally different gene complexes in the different species. The concept of homology in terms of similar genes handed on from a common ancestor has broken down... (as quoted in Fix, 1984, p.189).

Yet textbooks and teachers still continue to proclaim that humans and chimps are 98% genetically identical. The evidence clearly demonstrates vast molecular differences—differences that can be attributed to the fact that humans, unlike animals, were created in the image and likeness of God (Genesis 1:26-27; see Lyons and Thompson, 2002a, 2002b). Elaine Morgan commented on this difference.

Considering the very close genetic relationship that has been established by comparison of biochemical properties of blood proteins, protein structure and DNA and immunological responses, the differences between a man and a chimpanzee are more astonishing than the resemblances. They include structural differences in the skeleton, the muscles, the skin, and the brain; differences in posture associated with a unique method of locomotion; differences in social organization; and finally the acquisition of speech and tool-using, together with the dramatic increase in intellectual ability which has led scientists to name their own species Homo sapiens sapiens—wise wise man. During the period when these remarkable evolutionary changes were taking place, other closely related ape-like species changed only very slowly, and with far less remarkable results. It is hard to resist the conclusion that something must have happened to the ancestors of Homo sapiens which did not happen to the ancestors of gorillas and chimpanzees (1989, pp. 17-18, emp. added).

That “something” actually is “Someone”—the Creator.

REFERENCES

Barbulescu, Madalina, Geoffrey Turner, Mei Su, Rachel Kim, Michael I. Jensen-Seaman, Amos S. Deinard, Kenneth K. Kidd, and Jack Lentz (2001), “A HERV-K Provirus in Chimpanzees, Bonobos, and Gorillas, but not Humans,” Current Biology, 11:779-783.

Britten, Roy J. (2002), “Divergence between Samples of Chimpanzee and Human DNA Sequences is 5%, Counting Intels,” Proceedings of the National Academy of Sciences, 99:13633-13635, October 15.

Coghlan, Andy (2002), “Human-chimp DNA Difference Trebled,ׇ [On-line], URL: http://www.newscientist.com/news/news.jsp?id=ns99992833, September 23.

Fix, William R. (1984), The Bone Peddlers: Selling Evolution (New York: Macmillan).

Fujiyama, Asao, Hidemi Watanabe, et al., (2002), “Construction and Analysis of a Human-Chimpanzee Comparative Clone Map,” Science, 295:131-134, January 4.

Gardner, Eldon J. (1968), Principles of Genetics (New York: John Wiley and Sons).

King, Mary-Claire and A.C. Wilson (1975), “Evolution at Two Levels in Humans and Chimpanzees,” Science, 188:107-116, April 11.

Lyons, Eric and Bert Thompson (2002a), “In the ‘Image and Likeness of God’ [Part I],” Reason & Revelation, 22:17-23, March.

Lyons, Eric and Bert Thompson (2002b), “In the ‘Image and Likeness of God’ [Part II],” Reason & Revelation, 22:25-31, April.

Marks, Jonathan (2000), “98% Alike? (What Similarity to Apes Tells Us About Our Understanding of Genetics),” The Chronicle of Higher Education, May 12.

Morgan, Elaine (1989), The Aquatic Ape: A Theory of Human Evolution (London: Souvenir Press).

Muchmore, Elaine A., Sandra Diaz, and Ajit Varki (1998), “A Structural Difference Between the Cell Surfaces of Humans and the Great Apes,” American Journal of Physical Anthropology, 107[2]:187-198, October.

Pennisi, Elizabeth (2002), “Jumbled DNA Separates Chimps and Humans,” Science, 298:719-721, October 25.

Shouse, Ben (2002), “Revisiting the Numbers: Human Genes and Whales,” Science, 295:1457, February 22.

Sinnot, E.W., L.C. Dunn, and T. Dobzhansky (1958), Principles of Genetics (Columbus, OH: McGraw Hill) fifth edition.

Schwabe, Christian (1986), “On the Validity of Molecular Evolution,” Trends in Biochemical Sciences, 11:280-283, July.

“A Tiny Worm Challenges Evolution” (no date), [On-line], URL: http://www.cs.unc.edu/plaisted/ce/worm.html.

Toder, R. F. Grutzner, T. Haaf, and E. Bausch (2001), “Species-Specific Evolution of Repeated DNA sequences in Great Apes,” Chromosome Research, 9:431-435.

Zuckerkandl, Emile (1963), “Perspectives in Molecular Anthropology,” Classification and Human Evolution, ed. S.L. Washburn (Chicago, IL: Aldine).



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