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Author Topic:   Question about evolution, genetic bottlenecks, and inbreeding
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 30 of 123 (503104)
03-16-2009 6:31 AM
Reply to: Message 26 by harry
03-15-2009 10:23 PM


Nope
NO, it can only refer to ONE INDIVIDUAL or one paring of individuals if you are looking for both male and female.
Look at it this way (say we are looking for male). If I ask you to tell me your most recent common ancestor with your brother/sister, there is no way that is going to be a group, it is your father, end of story.
Your FIRST (HENCE MOST RECENT) common ancestor with your cousin, is your grandfather (or would it be your uncle? as staga pointed out its relation not descendancy, either way it does not matter), because he is related to both you and your cousin with genes.
You may very will have more than one common ancestor with your cousin, but you only have ONE most recent.
Not at all. Consider the following picture ... I'm not sure for what technical reasons it comes out looking so odd, I think it presupposes a white background.
Individuals A - H all have the status of MRCA of the group consisting of the group consisting of S, T, U, V, W, X, Y and Z.
H is Mitochondrial Eve.
The image is taken from the SkepticWiki article on Mitochondrial Eve, which you might want to read.

This message is a reply to:
 Message 26 by harry, posted 03-15-2009 10:23 PM harry has replied

Replies to this message:
 Message 31 by harry, posted 03-16-2009 6:50 AM Dr Adequate has replied
 Message 35 by harry, posted 03-16-2009 7:17 AM Dr Adequate has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 34 of 123 (503109)
03-16-2009 6:59 AM
Reply to: Message 31 by harry
03-16-2009 6:50 AM


Re: Nope
Re: Nope
So why is H eve and not F? She also seems to be related to everyone.
A, B, C, D, E, F, G and H are all common ancestors of the current generation. That was my point.
However, only H is the ancestor of everyone through the female line. Hence, individuals S through Z all inherited their mitochondria from H, and she is Mitochondrial Eve.
Edited by Dr Adequate, : No reason given.

This message is a reply to:
 Message 31 by harry, posted 03-16-2009 6:50 AM harry has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 45 of 123 (503126)
03-16-2009 9:23 AM
Reply to: Message 38 by harry
03-16-2009 7:33 AM


Re: Nope
Yes I do agree, but if one is the Y-adam it elevates him to the position of MRCA.
Like I said, you can say that, but I am talking about a definition, an important one. It isn't semantics, because these defintions can not be confused, and I am still confused.
I am asserting that Y-adam is the MRCA because that is what I have seen so far. You have all talked the talk, but you are not saying, look at this, according to this defintion, All of these people are MRCA, you have just pointed to a graaph, with an explanation of a relevant, but different topic on mitrochondrial eve.
You have basically posted a graph and said 'by my definition all these people are the MRCA.'
by my defintion it is Y-adam.
Who is right? IF you can show me I am wrong with a good reference, I will believe you.
I don't think a "good reference" is necessary to explain the meaning of the term "most recent". It means what it says.
Y-nuclear Adam is the MRCA in the male line, and is unique.
Mitochondrial Eve is the MRCA in the female line and is unique.
However, there need not be such a person as the, unique, MRCA, because, as the diagram shows, it is possible for a population to have a number of common ancestors all of whom are equally recent.

This message is a reply to:
 Message 38 by harry, posted 03-16-2009 7:33 AM harry has replied

Replies to this message:
 Message 46 by harry, posted 03-16-2009 9:26 AM Dr Adequate has replied
 Message 48 by Dr Adequate, posted 03-16-2009 9:40 AM Dr Adequate has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 47 of 123 (503129)
03-16-2009 9:33 AM
Reply to: Message 46 by harry
03-16-2009 9:26 AM


Re: Nope
When we discuess scientific definitions things do not always mean what they say though do they. IF they did, we wouldnt need defintions.
The definitions of "most" and "recent" aren't different in biology.
I have found these definitions, and you are saying they do not matter. Ofcourse they matter, the are written by emininent biolgists for a reason.
Quote these eminent biologists.
You can not just brush aside these defintions, there must be a way to reconcile/disprove why an individual is not guarenteed to be an MRCA at some point down the line.
I didn't follow that.
How do I upload pictures?
You don't. You put img tags around the internet address of the picture you want to display. If it doesn't have an internet address, upload it to an image hosting site such as ImageShack.
Edited by Dr Adequate, : No reason given.

This message is a reply to:
 Message 46 by harry, posted 03-16-2009 9:26 AM harry has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 48 of 123 (503130)
03-16-2009 9:40 AM
Reply to: Message 45 by Dr Adequate
03-16-2009 9:23 AM


Re: Nope
Further to my previous remarks, consider the possibility that individuals C and D lived, or reproduced, later than A, B, E, F, G and H (which is perfectly possible as generations don't go regularly like the ticking of a clock).
Then they would be more recent than Adam or Eve. Adam would still be the MRCA in the male line, but not an MRCA. Eve would still be the MRCA in the female line, but not an MRCA.

This message is a reply to:
 Message 45 by Dr Adequate, posted 03-16-2009 9:23 AM Dr Adequate has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 66 of 123 (503187)
03-16-2009 5:27 PM
Reply to: Message 54 by harry
03-16-2009 1:28 PM


Re: Would you Adam and Eve it?
'Concestor 0 is the most recent ancestor that unites the geograpahically divided population' Dawkins, page 45 ancestors tale.
See graph on page 49 of the book to see how ONE PERSON is the most recent common ancestor of all mankind.
But the graph does not show that this must be a unique distinction. Nor does Dawkins say so.
However, if we consider not just our all-female and
all-male lines, but our ancestors along all parental lines,
it turns out that everyone on earth may share a common
ancestor who is remarkably recent....that the
common ancestor of everyone alive today very likely lived
between 2,000 and 5,000 years ago.
That we have a common ancestor is not in doubt. That we have a unique MRCA will never be withing our power to prove, and Douglas Rhode does not say so.
---
As my diagram has shown, there can be more than one MRCA.
This is by-the-by. We may or may not have had a unique MRCA. Do you understand now why that person did not constitute a bottleneck?
---
If we assume the top two people on the chart are Y-adam and M-Eve ...
That can't be M-Eve unless she had some daughters.
If anyone here can draw me a tree disproving that there must have at some point been someone who is the ancestor of all humans. I'll shut up.
That's not being disputed.
But I am 99% sure that a Most recent common ancestor is an individual
A most recent common ancestor is an individual.
---
Please note once again that even if there was a unique MRCA, neither M-Eve nor YN-Adam need have been that individual. The odds are aginst it.

This message is a reply to:
 Message 54 by harry, posted 03-16-2009 1:28 PM harry has replied

Replies to this message:
 Message 67 by harry, posted 03-16-2009 5:34 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 70 of 123 (503191)
03-16-2009 6:03 PM
Reply to: Message 67 by harry
03-16-2009 5:34 PM


Re: Would you Adam and Eve it?
Do you actually read my posts or do you just skip over them. I have re-iterated since my like 4th post I know its not a bottle neck now.
I've not been memorizing your every word ...
Fine throw a daughter into the mix to go off and breed of the line
That's not good enough ... she needs to be the female-line ancestor of every female on that chart with living female-line descendants.
So why are people going against me on this.
People have said the MRCA can be a group of people, which if we are talking about grandparents fine, I will accept.
But if they think as a species we don't have one, they are off the bat.
We have at least one.
Are you contradicting yourself?
No. A most recent common ancestor is necessarily an individual for the same reason that a pretzel vendor is necessarily an individual --- that's just grammar.
However, the distinction need not be unique (see the diagram from the SkepticWiki).

This message is a reply to:
 Message 67 by harry, posted 03-16-2009 5:34 PM harry has replied

Replies to this message:
 Message 71 by harry, posted 03-16-2009 6:14 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 74 of 123 (503199)
03-16-2009 7:02 PM
Reply to: Message 71 by harry
03-16-2009 6:14 PM


Re: Would you Adam and Eve it?
Re: Would you Adam and Eve it?
You are starting to bore me now. No one has come up with anything that proves we can not be from one ancestor.
We have more than one ancestor.
We have at least one MRCA.
We may have more than one MRCA.
The definition of MRCA is THE MOST RECENT COMMON ANCESTOR.
Oh, you believe me now?
All you are doing is talk talk talk.
Well, this is the internet. If you would instead prefer me to whack you over the head with an inflated pig's bladder, I shall need traveling expenses.
You can not show me one paper that says I am wrong.
This is because there is no such thing as the Journal of the Bleedin' Obvious.
I am going to show the logical inevitability of my argument.
Bet?
Look once more at the diagram from the SkepticWiki. Individuals A through H are all contemporaries, and all common ancestors of the present generation.
Your argument cannot be "logically inevitable" if it is possible to conceive of a counterexample. And that is a counterexample.
Answer the question and only the question
Was there one creature that was related to all living chimpanzees and all living humans? Yes or No? Eveything related to this creature, ie its parents etc, are also common ancestors, but not relevant.
But is there only one creature that is the most recent common ancestor of you, and poopflinger the chimp?
How would I know?

This message is a reply to:
 Message 71 by harry, posted 03-16-2009 6:14 PM harry has replied

Replies to this message:
 Message 76 by harry, posted 03-16-2009 7:13 PM Dr Adequate has replied
 Message 80 by harry, posted 03-16-2009 7:48 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 79 of 123 (503206)
03-16-2009 7:44 PM
Reply to: Message 76 by harry
03-16-2009 7:13 PM


Re: Would you Adam and Eve it?
Yeah I didnt think you could
To what verb is "could" an auxiliary?
You clearly take me for an idiot and have not been reading any of my posts.
I have repeatedly stated it is the most recent common ancestor. Yuo say you have not memorised my posts word for word, you have not even read the basic points of them either.
You seemed to be in some doubt in post #46.
THIS IS NOTHING TO DO WITH THAT DIAGRAM. I HAVE NOW SAID REPEATEDLY, IAM NOT REFFERING TO GRANDPARENT MODELS ETC I AM TALKING ABOUT MRCA'S FOR GEOGRAPHICALLY DIVIDED POPULATIONS OR WHOLE SPECIES
Now imagine that individuals S, T, U and V go off and live on an island, and W, X, Y and Z stay on the mainland. Then their descendants diverge genetically so much that they speciate.
Where is the unique MRCA of the two resulting geographically divided species? They don't have one, do they?
Go back, re read everything I have said, then answer the question on what you think is the most likely answer to this question
Do we have a single MRCA that is related both chimpanzees and humans, yes or no?
If you are now asking me which is most likely, does that mean that you concede that both are possible?
I haven't figured out which is the most likely. If you believe that you have, please show your working. All I have maintained is that both are possible.

This message is a reply to:
 Message 76 by harry, posted 03-16-2009 7:13 PM harry has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 104 of 123 (503270)
03-17-2009 6:46 AM
Reply to: Message 80 by harry
03-16-2009 7:48 PM


Re: Would you Adam and Eve it?
Ok, I guess you guys are never going to trust me, so unless some one wants to play my logic game, and let me explain my line of reasoning literally step by step by answering the question
'do chimps and humans have one single Most recent common ancestor?'
We don't know. You don't know.
In the mean time, I really do recommend you pick up the the Ancestor's tale by Richard Dawkins it is an excellent book and it where i am getting my argument from.
I've read it. I have it in my lap as I type. Dawkins argues, correctly, for the existence of a MRCA, but I don't see where he argues for uniqueness. Indeed, he mentions the possibility of there being two. And, as my counterexample shows, there can be more.
In the mean time I will let you mull over this. If you dont believe Dawkins on evolution, you sure as heck will not believe me:
Any set of us must converge upon A SINGLE CONCESTOR (or couple(me: I'll let that slide for now, I am argueing that if we go further back it is one, still Dawkins is limiting the number to two,))
...Where we can start looking for Concestor 0, THE most recent ancestor of surviving humans.
The graph chart on page 39 is also clear in reffering to a single person.
But I have provided you with a counterexample showing that the MRCA need not be unique. Against this, no argument from authority is going to stand up, even if Dawkins had claimed to have proved uniqueness, which he didn't.
I came on this forum asking how we can be descended from one ancestor and avoid the problem of inbreeding, that question has been answered for me, and then I find people trying to say that we dont only have one most recent.
No, you find people saying that we need not have only one MRCA.
So if anyone will let me, I will explain to them my line of reasoning, but i am really only good at this if I can ask questions, and the questions be answered, as it ensures you yourself are whittling down the possibilites.
Then once it is explained, you can take it or leave it.
So for anyone who is interested, once again:
'do chimps and humans have one single Most recent common ancestor?'
We don't know. And we have absolutely no way of finding out.
Does that answer help you to "whittle down the possibilities"?

This message is a reply to:
 Message 80 by harry, posted 03-16-2009 7:48 PM harry has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 106 of 123 (503272)
03-17-2009 7:23 AM
Reply to: Message 97 by Stagamancer
03-16-2009 8:55 PM


Re: Would you Adam and Eve it?
However, in order to get multiple MCRAs as I've just pointed out in recent posts requires extreme inbreeding between cousins (3rd gen) or where sets of brothers marry sets of sisters (2nd gen). So the diagram proves it's not a inevitability, but I doubt that diagram is an accurate representation of the norm.
I think that's just an artifact of the necessity to keep the diagram small.

This message is a reply to:
 Message 97 by Stagamancer, posted 03-16-2009 8:55 PM Stagamancer has replied

Replies to this message:
 Message 110 by Stagamancer, posted 03-17-2009 2:48 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 123 of 123 (503453)
03-19-2009 8:29 AM
Reply to: Message 110 by Stagamancer
03-17-2009 2:48 PM


Re: Would you Adam and Eve it?
Agreed, which is why I don't think it is an accurate representation of the norm, and why you end up with all four couples in the 1st generation being MRCAs for the 4th.
No, I don't think that's the reason.
Let us define a "stem ancestor" as one having the following properties:
(a) S/he is an ancestor of everyone alive today.
(b) None of his/her children have property (a).
Now, intuitively, their ought to be quite a lot of these. It is possible to come up with family trees where there's only one, and even to come up with such family trees such that that there isn't a bottleneck: but it takes effort: such family trees are extremely factitious.
Now the question is: what are the odds that the most recent stem ancestors are contemporaries? (Of course, if they practice strict monogamy, the answer is 100%, and we should have to ask a slightly different question.)
Now the SkepticWiki diagram is artificial in that it puts all the stem ancestors in the same generation, again, to make the diagram neater. However, I'm not sure that the small population size is significant.
I might do a computer simulation at some point and try to see how population size affects the odds, but the question has no real biological significance, so don't hold your breath.

This message is a reply to:
 Message 110 by Stagamancer, posted 03-17-2009 2:48 PM Stagamancer has not replied

  
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