Question about evolution, genetic bottlenecks, and inbreeding

So why is H eve and not F? She also seems to be related to everyone.Edited by harry, : No reason given.

Trace everybody back through their mothers, they all lead back to H, not F.

Hi Harry,Welcome to EvC The primary cause of inbreeding depression is the creation of individuals who are homozygous for deleterious alleles. But, conversely, it also concentrates the advantageous alleles. These two factors interact to produce an optimal level of inbreeding; usually around the 2nd or 3rd cousin range, but as close as 1st cousins in some species.What can happen in small populations (especially among plants) is that although inbreeding reduces the individual fitness of early generations, the overall process can weed out individuals heterozygous for deleterious alleles and thus increase the average fitness of the population.

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.

Ok I go, that, but then in there is a Y - adam, person A.He is the MRCA.So therefore, A is the male MRCA, H is the female.All the others are common ancestors but not most recent. To the whole population.A pretty rubbishy source but a quick google search reveals
Page not found - Tripatlas'Y-chromosomal Adam' ('Y-mrca')Wikipedia:most recent common ancestor (MRCA) of any set of organisms is the most recent individual from which all organisms in the group are directly descendedThe two evolution books I have on the topic also refer to the MRCA as one distinct individual.We are beyond my question now. I understand fully how one MRCA can exist without the problem of inbreeding, as the mitrochondiral eve graph represents. However, it is innapropiate to use the same graph to say 'they are all the MOST recent common ancestor. All, common, sure, not most recent.Can anyone quote a peer reviewed source to tell me this is wrong? It is the only conclusion I can seem to get, and staga seemed to agree.Edited by harry, : No reason given.

Each of the ancestors A-H are equally far from the offspring at the end, therefor they're equally recent.

But they are all equally recent. They are all direct ancestors. You agree with that, right?

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.

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Each of the ancestors A-H are equally far from the offspring at the end, therefor they're equally recent.

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You need to back it up with a reasonEdited by harry, : No reason given.Edited by harry, : No reason given.

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I know I am correct. I think I'll play dumb for a little bit. First, you disagreed with me. Then you said I was correct. I think you have an integrity issue here. I think you are caught in a web of lies that you've resorted to contradicting yourself. Do you lie often?

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Interesting. The person who admits they used to be a creationist, first to get overtly rude, first to 'KNOW' they are right. A poor outlook to take in this subject.An interesting psychology experiment it would make, to study how confident one is their opinions, and whether or not these people correlate with religiousity.Don't like that? How about we drop the insults then and talk about the subject.

MRCA and Y-adam are different concepts, you're conflating and confusing them. In reality, the MRCA of all humans is much more recent than our Y-adam (which makes if you think about it, mitochondrial eve traces the female line only, Y-adam by the male line only, and the MRCA by both).

What is magical or special about Y-adam that makes him the MRCA? The most recent common ancestor is simply the ancestor that is more recently common to the organisms under question. In the diagram shown, T and W are siblings (brother and sister). Therefore, the ancestor that they most recently have in common with each other are their parents. So the MRCAs of T and W are the second couple (from left to right) in the third generation.Who is the most recent common ancestor of S and T? Well, not their parents, however, their fathers are brothers which means the most recent common ancestor is the first couple (from left to right) in the second generation.But wait a minute, their S and T's mothers are sisters too! That means the most recent common ancestor is the third couple (from left to right) in the second generation.In technical terms - it's a bit of a mess.Unfortunately, we rarely have a perfect genealogy like this diagram so we can only go by tracing certain things like the mitochondria. However, this doesn't necessarily get us to the most recent common ancestor, just a common ancestor that is the most recent common matrilineal ancestor. The actual common ancestor is almost certainly going to be more recent than that. So 'Adam' and 'Eve' just give us maximum distances to the most recent common ancestor, but we know it must be closer (in our diagram S and T have more recent ancestors in common with one another even thought their matrilineal common ancestor was from a generation earlier).Edited by Modulous, : No reason given.

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What is magical or special about Y-adam that makes him the MRCA?

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There is nothing magical about him, that is just the definition. IN THIS CONTEXT.I may have misreprestned myself, I am saying that for this example Y-adam and M-eve are the most recent common ancestors. I realise they are all the most recent, but as a definition it is A and H??No one has dealt with the fact that all the definitions I have found refer to the MRCA as an individual, not a group. If you can address this the conversation is complete. IF I am reading the definition wrong, what do they mean by individualHowever you have shown me you can have more than one equal generation common ancestor. So what makes one THE most recent common ancestor, there must be something because all these defintions I find refering to a single person would be baseless.These definitions that the MRCA is an individual must be based on something, no one has said yet.Edited by harry, : No reason given.

MRCA, mitochondrial Eve and y-chromosome Adam can all be individuals - however they can all also be populations.Taking it theoretically, if we look just as the MRCA, it's possible that it's a single individual, because they could have parented multiple offspring with different partners, or it could be that the MRCA was a couple who only had children together in which case both parents are equally recent ancestors.Secondly, on a more practical level, we can't find individuals from genetic data. Eve and Adam are both traced by unmodified genetic data passed by the maternal and paternal lines (respectively) so the only modifications in these lines are mutations, however we only get data when a modification occurs, so there is no way to distinguish between a small population that had the same markers and a single individual.On both grounds then, it is better to talk of these common ancestors on the basis of small populations than as single individuals.Oh, and another very important point: even if you consider y-chromosome Adam and mitochondrial Eve to represent individuals, this does not mean that they were the only individuals alive at that time, only that the very narrow piece of genetic material being tested hails from them.Edited by Mr Jack, : Another point.

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Secondly, on a more practical level, we can't find individuals from genetic data. Eve and Adam are both traced by unmodified genetic data passed by the maternal and paternal lines (respectively) so the only modifications in these lines are mutations, however we only get data when a modification occurs, so there is no way to distinguish between a small population that had the same markers and a single individual.

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I know, but I am talking purely theoritically

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Oh, and another very important point: even if you consider y-chromosome Adam and mitochondrial Eve to represent individuals, this does not mean that they were the only individuals alive at that time,

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I am also aware of that

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only that the very narrow piece of genetic material being tested hails from them MRCA was a couple who only had children together in which case both parents are equally recent ancestors

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Ok so this is my point. If we reach this point, where we have narrowed down the most recent common ancestor down to two people in our quest to find one (if my definition is correct). Plenty of others could have contribured to the gene pool, but these are the direct ancestors.However we still need to go further back to find the one person these 2 people are directly descended from. Because, and this is the crux of it, (Althought I am note sure. If the common ancestor of everyone today, had kids with only one woman as you suggest, they would both the M-Eve and Y-Adam, as they are both the most recent examples of where everyone got their chromosomes.Now we are pretty sure this isnt how it goes. How do I upload an image to show what I mean?

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can all be individuals

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All the definitions I find say they ARE. not can can be

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.