The Genetic Similarity of Apes and Humans

From the December 2012 issue of Creation Answers, by Wayne Spencer
 

Evolutionists have long made statements to the effect that the DNA of Chimpanzees is about 98% the same as that of Humans. So, they say this argues for today’s apes and today’s humans both evolving from a common ancestor.  That hypothetical ancestor is believed by evolutionists to have lived about 3 to 6 million years ago.  The exact percentage used in this argument may vary from different sources.  You might hear a percentage of 95%, for instance.  But these high percentages are misleading because of the complex issues with comparing the DNA of apes with the DNA of humans.  In recent years a great deal has been learned about the human genome and the chimpanzee genome.  This is definitely not my field of expertise but I feel there is so much new information from research on this topic that I should write something about it.  

    First, consider the similarity of animals from a creation perspective.  There are bound to be some similarities between different living things, especially between different mammals like apes and humans, because we are designed to live on the same planet.  Apes and humans do have similarities and may eat similar foods.  Some mammals are trained to be in circus acts or are adopted as pets.  If there were not similarities between humans and other mammals, it might be difficult for us to manage them, have them as pets, or to train them.  So I would see the similarities between us and other mammals as being for our benefit and for the sake of us learning from God’s creation.  

    But how do you measure the similarities between humans and animals?  This has been approached in different ways and incorporated into evolutionary theory.  Evolution says that the similarities between living things is generally a result of genetic changes over long periods of time as living things have evolved from a common ancestor of the past.  There are exceptions where evolutionists might say that some characteristics evolved more than once rather than coming about from a common ancestor.  Flight is like this for example because there are four different mechanisms for flight among living things.  If you compare  birds, extinct flying reptiles, bats, and insects, they all have somewhat different mechanisms for flight.  These are not believed to be due to a common ancestor because there is no plausible common ancestor for this.  On the other hand, apes and humans have many obvious similarities and it is believed that long ago there was an ape-man intermediate, called a hominid, that evolved by two different paths, one leading to modern apes and the other leading to humans.

    A common means of comparing different organisms today is what has been called molecular homology.  Homology is about the similarities of different organisms coming from a common ancestor by evolution.  Molecular homology does not consider body characteristics per se but compares DNA nucleotide sequences between organisms to calculate mathematically how similar they are.  But a question remains even today, Do scientists know how to compare the DNA of different organisms?  The answer to this question is complicated, but much has been learned in recent years from genetic genome research.  The genomes (complete DNA sequences) of some organisms have been mapped today and evolutionists have been busy looking for confirmations of evolutionary theory.  

    Before focusing specifically on the DNA comparisons for chimpanzees and humans, it is good to consider the bigger picture.  In the mid-1980's, a molecular biologist by the name of Michael Denton, an evolutionist, published a book called “Evolution: A Theory in Crisis.”  This book pointed out how a number of the common arguments for evolution did not work.  One of the best portions of the book was about molecular comparisons of different organisms.  If evolution is true the molecular comparison of a protein that is used in different organisms should differ across different organisms according to how much evolutionary change there has been between them.  So for example if you compare a protein such as cytochrome in a bacteria to the cytochrome from wheat and another cytochrome of a horse for instance, the differences should reflect evolutionary changes.  The cytochrome protein is used in similar ways in different organisms but the molecule varies some in its exact structure in different organisms.  Assuming evolution, the cytochrome of yeast should be closer to being like the cytochrome of a bacterium than it is to the cytochrome from a horse.  But this did not turn out to be the case, according to Denton.  Below is a table showing the percent differences between cytochrome molecules for different living things.  Again all these are comparing a particular bacterium’s cytochrome to the cytochrome for the organisms listed.  This is adapted from Chapter 12 in Denton’s book.¹

    The above table implies very different organisms do not show varying numbers for the molecular differences that reflect evolutionary development.  Notice that the Yeast for example, is more different from the bacteria than a human is!  The differences in this table essentially make different living things “equidistant” from each other, measuring this one thing of the cytochrome protein.  Evolutionists prior to this research would have expected the numbers in the table to decrease from the top rows to the bottom.  They would also have expected a larger change in the numbers.  These numbers only differ at most by 5%.  I think these numbers reflect creation better than evolution.  They reflect what Genesis 1 describes, organisms created “according to their kinds.”  But this is not a comparison of DNA.  This is only comparing one protein.  Man and Monkey may look similar from the table above, but since the other living things have similar numbers, it does not show evolution.  However, DNA is a more important comparison to make because DNA has a profound impact on the whole organism.

“Junk” DNA

    DNA is a very complex and compact information code.  About 2% of DNA codes for proteins and the remaining 98% does not code for proteins.  Evolutionists have often called the non-coding part “Junk” DNA.  The concept is that the non-coding portions, also called introns, are made up of unused leftover sequences that have come from countless generations of random changes.  However, a number of discoveries in recent years have shown that the introns, or “junk” portions are actually very important.  The portions of the DNA that codes for proteins are called exons.  The exons make up short sections that are spread out across the DNA sequence; they are not together in contiguous sections.  So in transcription, when the DNA is copied, the exon portions are spliced out and reconnected.  Scientists have found that the introns, the non-coding portions, are also transcribed and are used in the cell to regulate various processes.  The non-coding portions are thus very important and serious health conditions, including cancer, can be caused by the intron sections not being accurately transcribed.  So the “Junk” DNA sequences are not junk at all. Though this may be an oversimplification, the exon portions can be described as like data used by a computer program, and the introns are like the metadata about how to use the data, or like the computer program itself.  Jeffrey Tomkins is a creationist scientist at  the Institute for Creation Research (ICR) who has been working on research about human and chimpanzee DNA comparisons.  One of his articles had the following diagram explaining the introns and exons in DNA (CLICK TO GO TO).²

DNA Comparisons

    Just how similar is the DNA of apes to that of humans?  The answer to this depends greatly on what you compare.  To understand the issue with this, consider the following analogy.  Assume that someone was writing a series of books that was rewriting the story of J.R.R. Tolkein’s Lord of the Rings.  The Tolkein family would rightly try to prevent the work from being Plagiarized.  Let’s say that there is an author not working with the Tolkein family who has his own “copycat” version or modified version of the Lord of the Rings story.  

    Both sides in the legal battle may want to determine the degree that information has been plagiarized from the original books, to make the copy-cat story.  So the lawyers for the Tolkein family and the other author both develop computer programs to compare the words and phrases of the two books to see how much information is the same.  The Tolkein family might be able to obtain a higher percent of material copied by only comparing portions that are most similar.  The other author might go through the same process but get a lower percentage for the amount of material copied by only comparing the portions that are the most different.  The copycat story may omit parts of the original and may add insertions of new information not in the original.  Neither side of the Lord of the Rings comparison can analyze the entire book set because it is too much information.  So only portions are chosen and computer routines compare words and sentences to measure the amount of information that is the same between them.  Thus the Tolkein family could arrive at a high percentage of copied material, say 70% and the author of the copy-cat story could arrive at a lower amount of copied material, such as perhaps 40%.  

    This is very much like what scientists do in comparing the DNA sequence of apes, such as Chimpanzees, to human DNA.  When a percentage such as 98% is arrived at, it is not done by comparing the whole sequence of chimp DNA to the whole sequence of human DNA.  Significant portions are left out of the analysis for various reasons and only similar sequences are analyzed, so naturally a high percentage is the result.  First of all, in many such studies, only the exons (protein coding portions) are compared between the chimp and human DNA.  This means that only about 2 or 3 percent of the entire DNA is being compared and analyzed.  Also, there are sequences in one set of DNA that are not in the other.  These portions are called indels, which simply means insertions or deletions.  In sections where humans have information not in the chimp DNA these portions would have no similarity at all.  So these portions were generally not accounted for in many comparisons.  

    However, recent research is sometimes going beyond these limitations of previous studies and comparing portions not analyzed in the past.  There are also now creationist researchers that are redoing the research done by evolutionists to determine where evolutionary assumptions bias the results.  Creationists have been saying for years that the “Junk” DNA is not junk at all, we just haven’t known how it is used.  Now evolutionary scientists are sometimes coming to the same conclusion.  Evolutionary scientists are now getting percentages ranging from 70 to about 89 percent for the measure of similarity between chimpanzees and humans, when more data from the genomes are included in the analysis.

The Y Chromosomes

    There is one especially important recent finding in comparing the male Y chromosomes of chimpanzees and humans. Scientists were surprised to find major differences between human and chimp Y chromosomes.  Jeffrey Tomkins from ICR writes that the Y chromosomes have a number of major categories of sequences.  In one of these categories there was only about a 10% similarity between chimp and human.  Another category showed about a 50% similarity between chimp and human.  Also the human Y contains about 33% more categories of information that are entirely different from anything in chimpanzee Y chromosomes.  CLICK TO GO TO THIS ARTICLE.³  As Tomkins sums up, “the human and chimp Y chromosomes were constructed entirely differently.”  Tomkins gives an interesting but somewhat technical quote from the journal Nature explaining this about the Y chromosomes.  Tomkins puts it this way, “So, the human Y chromosome looks just as different from a chimp as the other human chromosomes do from a chicken.”

    Creationists are now reanalyzing some of the same data sets used by evolutionists to compare chimp and human DNA.  Modern apes also have 24 chromosomes compared to the 23 that humans have.  A theory put forward by evolutionists to explain this says that two chimpanzee number 2 chromosomes were fused together to make the human chromosomes.  But recent research on chromosome 2 is seriously challenging this theory as well.  CLICK TO GO TO THIS.¹¹  

    We could sum up by saying humans are humans and apes are apes.  Each are as God designed them to be.  Statements indicating that chimpanzee DNA is almost the same as human DNA are very misleading because of the way they use carefully selected data.  A more objective analysis including more of the genome agrees with a creation view.

Recommended Sources

1.  Denton, Michael, "Evolution:  A Theory in Crisis," Adler & Adler Publishers, 1985.
2.  http://www.icr.org/article/human-chimp-similarities-common-ancestry
3.  http://www.icr.org/article/new-chromosome-research-undermines
4.  Bergman, Jerry and Tomkins, Jeffrey, "Is the human genome nearly identical to chimpanzee? -- a reassessment of the literature," Journal of Creation, Creation Ministries International, 26(1), 2012, pp 54-60.
5.  http://www.answersingenesis.org/articles/arj/v4/n1/blastin
6.  http://www.answersingenesis.org/articles/arj/v4/n1/implications-for-comparative-genomics
7.  http://www.icr.org/article/human-chimp-genetic-similarity-do-shared
8.  http://creation.com/junk-dna-functions
9.  http://creation.com/dna-marvellous-messages-or-mostly-mess
10.  http://creation.com/chimp-y-chromosome
11.  http://www.icr.org/article/new-research-undermines-key-argument
 

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