Evolution and the 98% Chimpanzee

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Slide 2

The claim is often made that humans share up to 98% of the same DNA with chimpanzees – is this true?

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DNA is a linear array of four bases—A,G,C, and T

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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. -- Jonathan Marks

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Finding similarities does not prove common ancestry.

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Of the 5,000 best-known human genes, 75% have matches in the nematode

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“We share 98.8% of our DNA with chimpanzees and if that doesn’t make us just another animal then I don’t know what does. It’s worth remembering though that we also share about 50% of our DNA with bananas and that doesn’t make us half bananas, either from the waist up or the waist down. So there are limits in what genetics can tell us about what it means to be human.” -- Steve Jones

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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. “Jumbled DNA Separates Chimps and Humans” —October 25, 2002

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It is obvious that we are very different from chimpanzees in our appearance and way of life: if we are almost the same as chimpanzees in our DNA sequence, this simply means that DNA sequence is the wrong place to look in trying to understand what makes humans different. By this view, the 98.5% figure does not undermine the special place of humans. Instead it undermines the importance of genetics in thinking about what it means to be a human.

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We now know that the 98.5% figure is very misleading. In 2005 scientists published a draft reading of the complete DNA sequence (genome) of a chimpanzee. When this is compared with the genome of a human, we find major differences.

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To compare the two genomes, the first thing we must do is to line up the parts of each genome that are similar. When we do this alignment, we discover that only 2400 million of the human genome’s 3164.7 million ‘letters’ align with the chimpanzee genome – that is, 76% of the human genome. Some scientists have argued that the 24% of the human genome that does not line up with the chimpanzee genome is useless “junk DNA”. However, it now seems that this DNA could contain over 600 protein-coding genes, and also code for functional RNA molecules.

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Looking closely at the chimpanzee-like 76% of the human genome, we find that to make an exact alignment, we often have to introduce artificial gaps in either the human or the chimp genome. These gaps give another 3% difference. So now we have a 73% similarity between the two genomes.

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In the neatly aligned sequences we now find another form of difference, where a single ‘letter’ is different between the human and chimp genomes. These provide another 1.23% difference between the two genomes. Thus, the percentage difference is now at around 72%.

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We also find places where two pieces of human genome align with only one piece of chimp genome, or two pieces of chimp genome align with one piece of human genome. This “copy number variation” causes another 2.7% difference between the two species. Therefore the total similarity of the genomes could be below 70%.

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Our new knowledge of the human and chimpanzee genomes contradicts the idea that humans are 98% chimpanzee, and undermines the implications that have been drawn from this figure.

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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. 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.

Slide 22

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 five bone 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…

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Researchers say although for much of the past 150 years biology has largely concerned itself with filling in the details of the tree it is now obsolete and needs to be discarded.

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Dr. Eric Bapteste, an evolutionary biologist at the Pierre and Marie Curie University in Paris, said: “For a long time the holy grail was to build a tree of life. We have no evidence at all that the tree of life is a reality.”

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Current research is finding a far more complex scenario than Darwin could have imagined – particularly in relation to bacteria and single-celled organisms.

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Dr. Bapteste said: “If you don’t have a tree of life what does it mean for evolutionary biology. At first it’s very scary – but in the past couple of years people have begun to free their minds.”

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Dr. Rose said: “The tree of life is being politely buried – we all know that. What’s less accepted is our whole fundamental view of biology needs to change.”

Slide 35

The more one examines the evidence for evolution, the more apparent the many gaps, misrepresentations and oversimplifications become.

Slide 36

Lo, this only have I found, that God hath made man upright; but they have sought out many inventions. – Ecclesiastes 7:29

Slide 1

Evolution and the 98% Chimpanzee

Slide 2

The claim is often made that humans share up to 98% of the same DNA with chimpanzees – is this true?

Slide 3

DNA is a linear array of four bases—A,G,C, and T

Slide 4

Only 4 possibilities exist at any specific point in a DNA sequence Chance tells us that 2 random sequences from any species will match at about 1 in every 4 sites Even 2 unrelated DNA sequences will be 25% identical, not 0% identical

Slide 5

Finding similarities does not prove common ancestry.

Slide 6

Of the 5,000 best-known human genes, 75% have matches in the nematode

Slide 7

We also share about 50% of our DNA with bananas

Slide 8

That doesn’t make us half bananas, either from the waist up or the waist down. There are limits in what genetics can tell us about what it means to be human.

Slide 9

New research suggests that the 2 genomes might not be quite as similar after all. “Jumbled DNA Separates Chimps and Humans” Science magazine: October 25, 2002

Slide 10

It is obvious that we are very different from chimpanzees

Slide 11

If we are almost the same as chimpanzees in our DNA sequence, this simply means that … … the DNA sequence is the wrong place to look in trying to understand what makes humans different.

Slide 12

We now know that the 98.5% figure is very misleading

Slide 13

Only 76% of the human genome aligns

Slide 14

Artificial gaps are introduce to make an exact alignment

Slide 15

The difference is now at around 72%

Slide 16

Further copy and alignment differences cause more differences between the two species

Slide 17

The total similarity of the genomes could be below 70%

Slide 18

Our new knowledge of the genomes contradicts the idea that humans are 98% chimpanzee…

Slide 19

… and undermines the implications that have been drawn from this figure

Slide 20

The differences between a man and a chimpanzee are more astonishing

Slide 21

Differences include: Skeleton, Muscles, Skin, Brain, Posture, Locomotion, Speech, Tool-using, Intellect

Slide 22

Textbooks make much of the similarity between the limb skeletons of different animals to indicate their common origin.

Slide 23

If these structures were transmitted by the same genes, varied from time to time by mutations, the theory would make good sense. Unfortunately this is not the case.

Slide 24

The concept of homology in terms of similar genes handed on from a common ancestor has broken down…

Slide 25

Darwin originally thought that all life was related and could be traced back to a single simple life form

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He drew a tree diagram showing a proposed evolutionary pathway charting the different species.

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The tree would later grow to include more and more species.

Slide 28

Eventually this diagram becomes too complex

Slide 30

Researchers say although for much of the past 150 years biology has largely concerned itself with filling in the details of the tree it is now obsolete and needs to be discarded.

Slide 31

Dr. Eric Bapteste, an evolutionary biologist at the Pierre and Marie Curie University in Paris, said: “For a long time the holy grail was to build a tree of life. We have no evidence at all that the tree of life is a reality.”

Slide 32

Current research is finding a far more complex scenario than Darwin could have imagined – particularly in relation to bacteria and single-celled organisms.

Slide 33

Dr. Bapteste said: “If you don’t have a tree of life what does it mean for evolutionary biology. At first it’s very scary – but in the past couple of years people have begun to free their minds.”

Slide 34

Dr. Rose said: “The tree of life is being politely buried – we all know that. What’s less accepted is our whole fundamental view of biology needs to change.”

Slide 35

The more one examines the evidence for evolution, the more apparent the many gaps, misrepresentations and oversimplifications become.

Slide 36

Lo, this only have I found, that God hath made man upright; but they have sought out many inventions. – Ecclesiastes 7:29

Slide 37

truthseekers.ca

Summary: This presentation will address the claim that humans share up to 98% of the same DNA with chimpanzees.

Tags: evolution human chimpanzee ape 98% dna darwin homology science

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