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Author Topic:   The Common Ancestor?
Jon
Inactive Member


Message 76 of 341 (583657)
09-28-2010 12:37 PM
Reply to: Message 72 by Dr Adequate
09-28-2010 10:57 AM


Re: Ancestor in common; yes.
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.

While such an individual may have existed, I don't see why it is at all necessary or even reasonable to assume she did. What defines one as human vs. chimp is not locked away in a single gene. The speciation event would have taken many generations, during which input from any member of C (to use your example) could have occurred (which would make that person a B). It would be something like the following (P = Proto-):


PC PB PH
\ / \ /\
\ / \ / PH
PC PH |
| | |
/ \ / \ /
C B B H
| \/ |
|\ ?? /|
C \ / \ / H
? ?

So while we may have an ancestor in common, the question is with whom? With one another, sure; but with chimpanzees? I find it unlikely; not because we could not pinpoint the ancestor, but because the ancestor (singular) doesn't exist, at least not in any meaningful way. Who's the CA in the above diagram?

Jon


"Can we say the chair on the cat, for example? Or the basket in the person? No, we can't..." - Harriet J. Ottenheimer

"Dim bulbs save on energy..." - jar


This message is a reply to:
 Message 72 by Dr Adequate, posted 09-28-2010 10:57 AM Dr Adequate has not yet responded

Replies to this message:
 Message 78 by Dr Jack, posted 09-28-2010 12:43 PM Jon has responded
 Message 87 by PaulK, posted 09-29-2010 3:36 AM Jon has not yet responded

  
Jon
Inactive Member


Message 77 of 341 (583658)
09-28-2010 12:41 PM
Reply to: Message 75 by Taq
09-28-2010 12:08 PM


Re: The most recent common ancestor
Then we are only looking at the species that contains the most synapomorphies which still does not guarantee direct ancestry to any living organism, human or chimp.

It will be an okay first start though, no?


"Can we say the chair on the cat, for example? Or the basket in the person? No, we can't..." - Harriet J. Ottenheimer

"Dim bulbs save on energy..." - jar


This message is a reply to:
 Message 75 by Taq, posted 09-28-2010 12:08 PM Taq has not yet responded

  
Dr Jack
Member (Idle past 184 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 78 of 341 (583659)
09-28-2010 12:43 PM
Reply to: Message 76 by Jon
09-28-2010 12:37 PM


Re: Ancestor in common; yes.
Who's the CA in the above diagram?

PB is. Assuming time is supposed to be read down the diagram.

What are question marks supposed to be?


This message is a reply to:
 Message 76 by Jon, posted 09-28-2010 12:37 PM Jon has responded

Replies to this message:
 Message 79 by Jon, posted 09-28-2010 3:11 PM Dr Jack has responded

  
Jon
Inactive Member


Message 79 of 341 (583705)
09-28-2010 3:11 PM
Reply to: Message 78 by Dr Jack
09-28-2010 12:43 PM


Re: Ancestor in common; yes.
Who's the CA in the above diagram?

PB is.

Okay, that makes sense; but only as far as my chart goes, and the real process being not so neat, my chart is not representative of much other than a fantasized simplification. What if there are (and in reality, I'd think this likely) humans that have no input from PB@t1? Let's say we can extend as follows (I switched some more things to ?):


PC PB PH t1
| \ / \ /\
| \ / \ / PH
PC P? P? |
| | | |
| / \ / \ / \
PC C B B H H t2
| | | | | |
| |\ ? ? /| |
PC C \ / \ / H H
| | ? ? | |
| | | | | |
/ \| |\ |\/ \ / \
PC C ? ? ? ? H H t3
| \_|_____ _______/| (from C@t3 to C@t4 crosses OVER
| | \ / | PC@t3 to ?@t4; they do not connect)
PC C ?_________H t4
\ / |
C H t5

What is the CA for H and C at t5? I see we can find some ancestors in common, and naturally there must be (they are related species after all). But you cannot find a single one that shares all in common, unless you cut out some input from your consideration. If we answer CA for H&C@t5 as PB@t1, then we cut out CA for PH&PC from our consideration. It is an ancestor in common, but is it the most recent? Is it the most ancestral?

Assuming time is supposed to be read down the diagram.

Correct.

What are question marks supposed to be?

They are uncertainties as regards their classification.

Jon

Edited by Jon, : Can't cross a T if it isn't there...


"Can we say the chair on the cat, for example? Or the basket in the person? No, we can't..." - Harriet J. Ottenheimer

"Dim bulbs save on energy..." - jar


This message is a reply to:
 Message 78 by Dr Jack, posted 09-28-2010 12:43 PM Dr Jack has responded

Replies to this message:
 Message 80 by New Cat's Eye, posted 09-28-2010 3:17 PM Jon has not yet responded
 Message 81 by Dr Jack, posted 09-28-2010 5:32 PM Jon has not yet responded

  
New Cat's Eye
Inactive Member


Message 80 of 341 (583708)
09-28-2010 3:17 PM
Reply to: Message 79 by Jon
09-28-2010 3:11 PM


I don't think your chart accurately represents how reproduction and the emergence of new species works.

Just because you can make up a scenario where there wouldn't be a common ancestor doesn't mean that its anything possible here in reality.


This message is a reply to:
 Message 79 by Jon, posted 09-28-2010 3:11 PM Jon has not yet responded

  
Dr Jack
Member (Idle past 184 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 81 of 341 (583735)
09-28-2010 5:32 PM
Reply to: Message 79 by Jon
09-28-2010 3:11 PM


Re: Ancestor in common; yes.
PC@t3 is the most recent common ancestor of C and H@t5 in your diagram.

But to save you drawing more, and more, convoluted diagrams I'll point out that it is inevitably possible to draw a diagram that includes no common ancestor because you have control of the time window you choose to represent. The solution then for finding the common ancestor is to draw further backwards in time.

Might I suggest that rather than drawing further diagrams you address the logical argument that Dr. A presented a few posts back? It looks watertight to me.


This message is a reply to:
 Message 79 by Jon, posted 09-28-2010 3:11 PM Jon has not yet responded

Replies to this message:
 Message 82 by barbara, posted 09-28-2010 9:49 PM Dr Jack has responded
 Message 89 by caffeine, posted 09-29-2010 5:25 AM Dr Jack has responded

  
barbara
Member (Idle past 2881 days)
Posts: 167
Joined: 07-19-2010


Message 82 of 341 (583783)
09-28-2010 9:49 PM
Reply to: Message 81 by Dr Jack
09-28-2010 5:32 PM


Re: Ancestor in common; yes.
Dr A's drawing is not based on evidence. It is purely speculative. There is no DNA evidence of those species that lived 2.5 million yrs ago when they split. Today's DNA between them are not identical or even close. There are no fossils of gorilla and only a few of orangutan. The fossils of chimps look very much like they do today.

Genetics claim that a fresh water dolphin is not related to the salt water dolphin so do you really expect me to believe we are related to chimps based on a silly diagram? Please stop turning evolution into a religion before its loses all credibility. Common ancestry cannot be proven so why waste your time?


This message is a reply to:
 Message 81 by Dr Jack, posted 09-28-2010 5:32 PM Dr Jack has responded

Replies to this message:
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 Message 84 by Jon, posted 09-29-2010 12:48 AM barbara has not yet responded
 Message 85 by Dr Adequate, posted 09-29-2010 12:57 AM barbara has not yet responded
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crashfrog
Inactive Member


(1)
Message 83 of 341 (583799)
09-29-2010 12:36 AM
Reply to: Message 82 by barbara
09-28-2010 9:49 PM


Re: Ancestor in common; yes.
There is no DNA evidence of those species that lived 2.5 million yrs ago when they split.

The DNA evidence was handed down to their descendants.


This message is a reply to:
 Message 82 by barbara, posted 09-28-2010 9:49 PM barbara has not yet responded

  
Jon
Inactive Member


Message 84 of 341 (583800)
09-29-2010 12:48 AM
Reply to: Message 82 by barbara
09-28-2010 9:49 PM


Re: Ancestor in common; yes.
Genetics claim that a fresh water dolphin is not related to the salt water dolphin so do you really expect me to believe we are related to chimps based on a silly diagram? Please stop turning evolution into a religion before its loses all credibility. Common ancestry cannot be proven so why waste your time?

Common ancestry is a fact.

Today's DNA between them are not identical or even close. There are no fossils of gorilla and only a few of orangutan. The fossils of chimps look very much like they do today.

Too bad that's all false.

Jon


"Can we say the chair on the cat, for example? Or the basket in the person? No, we can't..." - Harriet J. Ottenheimer

"Dim bulbs save on energy..." - jar


This message is a reply to:
 Message 82 by barbara, posted 09-28-2010 9:49 PM barbara has not yet responded

  
Dr Adequate
Member
Posts: 16086
Joined: 07-20-2006
Member Rating: 10.0


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.


This message is a reply to:
 Message 82 by barbara, posted 09-28-2010 9:49 PM barbara has not yet responded

Replies to this message:
 Message 86 by Ken Fabos, posted 09-29-2010 2:45 AM Dr Adequate has not yet responded

  
Ken Fabos
Member (Idle past 336 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 86 of 341 (583805)
09-29-2010 2:45 AM
Reply to: Message 85 by Dr Adequate
09-29-2010 12:57 AM


Re: Ancestor in common; yes.
I haven't been keeping up with the debate here but I'd like to make the point that genes mutate within individuals to be 'dispersed' through a population through time by being passed to descendents. When that new gene has 'fixed' ie effectively carried by the whole population, that whole population has that mutant individual as an ancestor in common. Whilst the same mutation might theoretically occur independently in different individuals, the surest way for a beneficial mutation - for defining traits that predate homo sapiens diaspora - to fix in a gene pool is by inheritance whereas multiple independent mutations, being unlikely random changes within a genome that's quite large looks most unlikely for the spread of a specific gene into a foundation population. We have genes that are universal to our species (noting that sub-populations could lose some and still be homo sapiens) and they arose from individuals who passed them through their descendents through the intervening generations to us. We surely have multiple ancestors in common but one may have been further back than the others.

I've found This online intro to evolutionary biology a very useful resource for unravelling misunderstandings of how evolution works. Not that I fully understand all the processes or their implications.

Edited by Ken Fabos, : edit for clarity.


This message is a reply to:
 Message 85 by Dr Adequate, posted 09-29-2010 12:57 AM Dr Adequate has not yet responded

  
PaulK
Member
Posts: 14753
Joined: 01-10-2003
Member Rating: 1.7


Message 87 of 341 (583807)
09-29-2010 3:36 AM
Reply to: Message 76 by Jon
09-28-2010 12:37 PM


Re: Ancestor in common; yes.
quote:

While such an individual may have existed, I don't see why it is at all necessary or even reasonable to assume she did. What defines one as human vs. chimp is not locked away in a single gene. T

In fact Dr. A did give reasons why it IS necessary. Provided the divisions between the gorilla and human/bonobo/chimp lineages and the human and bonobo/chimp lineages are clean it must be the case.

To repeat the explanation in my words. Start with a common ancestor of living humans and bonobos/chimps from the ancestral population after the split with the gorilla lineage is complete. This individual (by definition) must have both human and bonobo/chimp descendants.

Either this individual has a child which also has both human and bonobo/chimp descendants or it does not. If it has such a child we move on to that child and repeat, at each stage choosing a child with both human and bonobo/chimp descendants.

Since we know that the lineages have diverged this process cannot go on forever. Therefore at some point we must find an individual who has human descendants and bonobo/chimp descendants, but no child with both human and bonobo/chimp descendants.

It follows that this individual must have at least one child with human descendants and no bonobo/chimp descendants and at least one child with bonobo/chimp descendants but no human descendants.

Therefore Doctor Adequate is correct


This message is a reply to:
 Message 76 by Jon, posted 09-28-2010 12:37 PM Jon has not yet responded

    
Dr Jack
Member (Idle past 184 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 88 of 341 (583815)
09-29-2010 4:58 AM
Reply to: Message 82 by barbara
09-28-2010 9:49 PM


Re: Ancestor in common; yes.
Why is this in reply to my message?

Dr A's drawing is not based on evidence. It is purely speculative. There is no DNA evidence of those species that lived 2.5 million yrs ago when they split. Today's DNA between them are not identical or even close.

2.5 million? Huh? The human/chimp split was much earlier than that. As for no evidence, you're just being silly. There is a tremendous amount of evidence that chimps and humans are more closely related to each other than they are to any other species.

There are no fossils of gorilla and only a few of orangutan. The fossils of chimps look very much like they do today.

So?

Genetics claim that a fresh water dolphin is not related to the salt water dolphin so do you really expect me to believe we are related to chimps based on a silly diagram?

Actually it says that fresh water dolphins are more closely related to each other than they are to salt water dolphins. Even that's a simplification since the Amazon River Dolphin is more closely related to the salt water La Plata Dolphin than it is to other river dolphins.

What is it about this you find implausible?

And, finally, no-one expects you to believe based on a diagram. The diagram Dr. A kindly provided for you is a summary of our knowledge on the subject not the evidence for it.


This message is a reply to:
 Message 82 by barbara, posted 09-28-2010 9:49 PM barbara has not yet responded

  
caffeine
Member
Posts: 1601
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 2.3


Message 89 of 341 (583816)
09-29-2010 5:25 AM
Reply to: Message 81 by Dr Jack
09-28-2010 5:32 PM


Re: Ancestor in common; yes.
PC@t3 is the most recent common ancestor of C and H@t5 in your diagram.

PC and C at t3 are equally recent common ancestors, both being the grandparents of C and H at t5.

The important point here, though, is that Jon's hypothetical drawings seem to be clearly demonstrating Dr. A's argument to be correct, as both examples clearly fit what Dr. A was saying. In the second, more complicated example, PC@t3 and C@t3 are in Dr. A's Set B - they have human and chimp living descendants. PC@t3 has three children listed - two of which (PC@t4 and C@t4) are in Set C (they have only chimp descendants) while one (?@t4) is in Set H - it has only human descendant. The same applies to C@t3, who has one child in Set C (C@t4) and one child in set H (?@t4).

What I think Job is discussing (correct me if I'm wrong!), is the idea that two populations may diverge, and then start to change such that they're recognisable as distinct populations, without genetic flow between them ceasing. So we'd have our protochimps and protohumans, still occasionally interbreeding for many, many generations even after recognisably seperating. This doesn't change the fact that the populations eventually do seperate completely with no further interbreeding, and there must at some point be the final ancestor who has both human and chimp descendants, but whose children do not.


This message is a reply to:
 Message 81 by Dr Jack, posted 09-28-2010 5:32 PM Dr Jack has responded

Replies to this message:
 Message 90 by Dr Jack, posted 09-29-2010 5:31 AM caffeine has responded
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Dr Jack
Member (Idle past 184 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 90 of 341 (583818)
09-29-2010 5:31 AM
Reply to: Message 89 by caffeine
09-29-2010 5:25 AM


Re: Ancestor in common; yes.
PC and C at t3 are equally recent common ancestors, both being the grandparents of C and H at t5.

Minor point: the line down from C crosses the line across from PC, it doesn't lead to H at all


This message is a reply to:
 Message 89 by caffeine, posted 09-29-2010 5:25 AM caffeine has responded

Replies to this message:
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