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Author Topic:   The Common Ancestor?
Dr Adequate
Member (Idle past 169 days)
Posts: 16112
Joined: 07-20-2006


Message 8 of 341 (582654)
09-22-2010 2:29 PM
Reply to: Message 6 by barbara
09-22-2010 1:42 PM


The neanderthal DNA also says we are 96% the same. They appear closer to humans then chimps yet the difference is still 4%. These percentages seem to contradict depending on what journal you read ...

The real difference is in what exactly you're counting.

Consider the following two genes (this is a made-up example, all real genes are longer).

ACTCGACGG

ACTTGACGA

How similar are they? If we count base-pairs, 77%. If we count codons, 33%. If we count genes, 0%. If we count proteins, 66%.

So when you see any figure cited, you should ask "percentage of what?" Different people would give different figures when talking about exactly the same data, depending on what exactly it is they're counting. Saying "96% the same" is actually rather meaningless unless you say how you're counting.

This may explain some of the apparent inconsistencies you see when people cite these figures.

There hasn't been any other species between Neanderthal and modern humans is there in the fossil record?

Neanderthals aren't ancestral to modern humans, they're a sister species. We don't expect there to be anything between them.


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 Message 6 by barbara, posted 09-22-2010 1:42 PM barbara has responded

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Dr Adequate
Member (Idle past 169 days)
Posts: 16112
Joined: 07-20-2006


Message 62 of 341 (583585)
09-28-2010 4:04 AM
Reply to: Message 61 by barbara
09-28-2010 1:52 AM


Re: Bad Analogies = Bad Science

|--------------- orangutans
---|
| |----------- gorillas
|---|
| |--- chimps
| |---|
|---| |--- bonobos
|
|------- humans

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Dr Adequate
Member (Idle past 169 days)
Posts: 16112
Joined: 07-20-2006


Message 63 of 341 (583586)
09-28-2010 4:22 AM
Reply to: Message 58 by Jon
09-27-2010 10:20 PM


Re: Ancestor in common; yes.
Having a specific individual that all our species can count as an ancestor doesn't seem outrageous to me.

It seems outrageous to me, and for good reason.

Hold your outrage. It would be remarkable if that individual uniquely held that distinction. It is inevitable that at least one individual did.

In fact, let me blow your mind a little.

There existed a common ancestor of all humans and chimps/bonobos who had two children, one of whom was the common ancestor of all living humans but no chimps/bonobos, and the other of whom was the common ancestor of all living chimps/bonobos but no humans.

Speciation does not show effects in single individuals.

Quite so. And the two children I just mentioned might for all I know have been identical twins.


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Dr Adequate
Member (Idle past 169 days)
Posts: 16112
Joined: 07-20-2006


Message 64 of 341 (583588)
09-28-2010 4:27 AM
Reply to: Message 56 by Strongbow
09-27-2010 8:26 PM


Re: SCOTUS Ruling Tactics = Bad Analogies
Common ERV's an excellent way to determine common ancestors ...

Common ancestry.


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Dr Adequate
Member (Idle past 169 days)
Posts: 16112
Joined: 07-20-2006


(1)
Message 72 of 341 (583642)
09-28-2010 10:57 AM
Reply to: Message 67 by Dr Jack
09-28-2010 7:43 AM


Re: Ancestor in common; yes.
Are you sure about this? Could we see a proof?

Hmmph. Actually, I'm having trouble making the last part of the argument truly rigorous.

For now, let's go for a weaker proposition: there was at least one individual having two children one of whom was ancestral to some or all living humans but no chimps/bonobos, and the other of whom was the ancestor of some or all living bonobos/chimps but no humans.

---

Consider humans, chimps, bonobos, the common ancestral species and all the intermediate species. Call this set Z. We can divide set Z into four mutually exclusive sets:

Set O: those with 0 living descendants.

Set H: those with only Human living descendants.

Set C: those with only Chimp/bonobo living descendants.

Set B: those with Both human and chimp/bonobo living descendants.

Set B is non-empty. For suppose otherwise. Then we would have no genetic connection between sets H and C except possibly crosses between them that fell into set O, and so were biological dead-ends. Sets H and C would then be in effect two separate clades running in parallel. But by definition Z contains the common ancestral group of H and C, so this is not possible.

So B has some members.

Not every member of set B can have descendants in B, because there is no-one alive today who is a member of set B. So there must be at least one member of B none of whose descendants are in B. Pick any such member of B and call this member B*.

But there are only two ways to be in set B. One is to have a descendant in set B --- which B* does not do by definition --- and the other is for B* to have at least one child in H and one in C.

This completes the proof.

---

Note that there is no proof or claim of uniqueness of B* and no biological grounds on which we should expect it. But there must be at least one.

---

I thought I had a rigorous proof of my original claim, but it keeps slipping through my fingers at present. In order to get at it this way I should have to show that the children of B* (call them H* and C*) were common ancestors of all living humans and of all living chimps/bonobos respectively, and although this seems very likely, I don't know any more that it can be proved certain even given additional biological considerations such as Dollo's law.

I shall have to think about this.

Edited by Dr Adequate, : No reason given.


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Dr Adequate
Member (Idle past 169 days)
Posts: 16112
Joined: 07-20-2006


Message 85 of 341 (583802)
09-29-2010 12:57 AM
Reply to: Message 82 by barbara
09-28-2010 9:49 PM


Re: Ancestor in common; yes.
Dr A's drawing is not based on evidence.

Yes it is --- it's based on DNA, morphology, and the fossil record.

Genetics claim that a fresh water dolphin is not related to the salt water dolphin

Yeah? Well it so happens that genetics are a personal friend of mine, and I was talking to genetics the other day, and genetics told me that they are most certainly related.

(I do wish people wouldn't write sentences like that.)

If you mean that some geneticist has claimed that, name the geneticist. If you mean that you claim that you have genetic evidence for that, show us the evidence.


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Dr Adequate
Member (Idle past 169 days)
Posts: 16112
Joined: 07-20-2006


Message 126 of 341 (585508)
10-08-2010 2:15 PM
Reply to: Message 123 by barbara
10-08-2010 12:13 PM


Re: Time Tree : : Timescale of Life
The confusion is that all of these critters that split with humans is indicating that we once were able to breed with these species.

No.

What would we have looked like when we split?

We wouldn't have looked like anything, 'cos of not having evolved yet.

However, to answer the question you should have asked, the immediate descendants of the common ancestor of humans and (for example) birds would have looked like reptiles, because that's what they were.

Is this indicating that we once were a chimp, mouse, horse,, elephant or a bird in the past?

No.

Good grief.


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Dr Adequate
Member (Idle past 169 days)
Posts: 16112
Joined: 07-20-2006


Message 127 of 341 (585509)
10-08-2010 2:16 PM
Reply to: Message 125 by barbara
10-08-2010 1:06 PM


Re: Time Tree : : Timescale of Life
You might as well state that we are all related by "name unknown" ancestrial breeding pair of a mouse/Human split because we at least can identify the mouse.

This tree also has the eukaryote/bacteria split to be 2622.2 mya. How could we have split from them when we are made of bacteria from a fusion between two different species of bacteria?

OK, you've convinced me, we're still bacteria ...

Oh, wait.

How can we not have split from them? We're vertebrates. They're blobs. Our potential for interbreeding is nil.

Edited by Dr Adequate, : No reason given.


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Dr Adequate
Member (Idle past 169 days)
Posts: 16112
Joined: 07-20-2006


(1)
Message 245 of 341 (693542)
03-17-2013 1:57 PM
Reply to: Message 243 by Just being real
03-17-2013 1:15 PM


Regarding the last common ancestor premise and creation, don't you agree that what you personally believe about what creationists predict or don't predict is only your opininon? Your claim is that creation doesn't predict that the "last common ancestor" premise, could also be the result of a common creator. That is your opinion isn't it? I have been involved in the debate for almost nine years now and all the creationists I have ever spoken with and most of the creationist websites I have veiwed do explain the similarities this way.

But creationists do not predict the pattern of similarities. They "explain" them, as you say, by saying goddidit that way (and even then that's using the term "explain" rather loosely) --- but there is nothing whatsoever in creationism that would predict them.


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Dr Adequate
Member (Idle past 169 days)
Posts: 16112
Joined: 07-20-2006


Message 252 of 341 (693555)
03-17-2013 6:26 PM
Reply to: Message 248 by Just being real
03-17-2013 3:05 PM


Alas, it appears that if you want to go on being wrong about this subject, you will have to do so in another thread. Or you could apply five seconds' thought to the matters on which you discourse so glibly; whichever you find less fatiguing.

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