Chimp genome sequence very different from man
by David A. DeWitt, Ph.D., director, Center for
Creation Studies, Liberty University, Lynchburg, VA, USA
5 September 2005
For many years, evolutionary scientists—and science museums and zoos—have
hailed the chimpanzee as “our closest living relative” and have pointed
to the similarity in DNA sequences between the two as evidence. In most previous
studies, they have announced 98-99% identical DNA.1 However, these were
for gene coding regions (such as the sequence of the cytochrome c protein), which
constituted only a very tiny fraction of the roughly 3 billion DNA base pairs that
comprise our genetic blueprint. Although the full human genome sequence has been
available since 2001, the whole chimpanzee genome has not. Thus, all of the previous
work has been based on only a portion of the total DNA.
Last week, in a special issue of Nature devoted to chimpanzees, researchers
report the initial sequence of the chimpanzee genome.2 No doubt, this
is a stunning achievement for science: deciphering the entire genetic make up of
the chimpanzee in just a few years. Researchers called it “the most dramatic
confirmation yet” of Darwin’s theory that man shared a common ancestor
with the apes. One headline read: “Charles Darwin was right and chimp gene
map proves it.”3
So what is this great and overwhelming “proof” of chimp-human common
ancestry? Researchers claim that there is little genetic difference between us (only
4%). This is a very strange kind of proof because it is actually double
the percentage difference that has been claimed for years!4 The reality
is, no matter what the percentage difference, whether 2%, 4%, or 10%, they still
would have claimed that Darwin was right.
Further, the use of percentages obscures the magnitude of the differences. For example,
1.23% of the differences are single base pair substitutions. This doesn’t
sound like much until you realize that it represents ~35 million mutations! But
that is only the beginning, because there are ~40–45 million bases present
in humans and missing from chimps, as well as about the same number present in chimps
that is absent from man. These extra DNA nucleotides are called “insertions”
or “deletions” because they are thought to have been added in or lost
from the sequence. (Substitutions and insertions are compared in Figure 1.) This
puts the total number of DNA differences at about 125 million. However, since the
insertions can be more than one nucleotide long, there are about 40 million separate
mutation events that would separate the two species.
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Substitution |
Insertion/deletion |
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Figure 1. Comparison between a base substitution and an insertion/deletion.
Two DNA sequences can be compared. If there is a difference in the nucleotides (an
A instead of a G) this is a substitution. In contrast, if there is a nucleotide
base which is missing it is considered an insertion/deletion. It is assumed that
a nucleotide has been inserted into one of the sequences or one has been deleted
from the other. It is often too difficult to determine whether the difference is
a result of an insertion or a deletion and thus it is called an “indel.”
Indels can be of virtually any length.
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To put this number into perspective, a typical page of text might have 4,000 letters
and spaces. It would take 10,000 such full pages of text to equal 40 million letters!
So the differences between humans and chimpanzees include ~35 million DNA bases
that are different, ~45 million in the human that are absent from the chimp and
~45 million in the chimp that are absent from the human.
Creationists believe that God made Adam directly from the dust of the earth just
as the Bible says. Therefore, man and the apes have never had an ancestor in common.
However, assuming they did for the sake of analyzing the argument, then 40 million
separate mutation events would have had to take place and become fixed in the population
in only ~300,000 generations—a problem referred to as “Haldane’s
dilemma.” This problem is exacerbated because the authors acknowledge that
most evolutionary change is due to neutral or random genetic drift. That refers
to change in which natural selection is not operating. Without a selective advantage,
it is difficult to explain how this huge number of mutations could become fixed
in the population. Instead, many of these may actually be intrinsic sequence differences
from the beginning of creation.
Some scientists are surprised at the anatomical, physical and behavioral differences
between man and chimpanzee when they see so much apparent genetic similarity. With
a philosophy that excludes a Creator God, they are forced to accept similarity as
evidence of common ancestry. However, similarity can also be the result of a common
Designer.
It is the differences that make the difference. The most important difference is
that man is created in the image of God.
Dr. DeWitt is the director of the Center for Creation Studies and
an associate professor of biology at Liberty University in Lynchburg, Virginia,
USA. His Ph.D. is in neurosciences from Case Western Reserve University and the
focus of his research is the cell biology of Alzheimer’s disease.
References
- DeWitt, D.A., >98.5% Chimp human DNA similarity?
Not anymore.
- The Chimpanzee Sequencing and Analysis Consortium 2005. “Initial sequence
of the chimpanzee genome and comparison with the human genome,” Nature
437:69–87.
- www.news-medical.net/?id=12840, August 31 2005.
- Studies of chimp-human similarity have typically ignored insertions and deletions
although this accounts for most of the differences. A study by Roy Britten included
these insertions and deletions and obtained a figure that is close to the 4% reported
here. Britten, R.J., “Divergence between samples of chimpanzee and human DNA
sequences is 5% counting indels,” Proceedings National Academy Science
99:13633–13635, 2002.
| It has been said that “Information is power”. When it comes to creation information we’d have to agree. Keep the ‘powerful’ evidence for God being Creator coming.  | | |
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