Question about evolution, genetic bottlenecks, and inbreeding

I think that's just an artifact of the necessity to keep the diagram small.

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'do chimps and humans have one single Most recent common ancestor?'

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Probably; although they might have an equally recent pair of ancestors and likely some other edge cases. But, the reasoning that leads to a MRCA for humans applies equally to humans and apes. However, it's not an interesting outcome, and it is not what people are talking about when they talk about the common ancestor of humans and apes, which is a species or population, not an individual.

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I know we are talking about a species when I say that, but I am talking theoritically, which I guess I have been proved incorrect on.Edited by harry, : No reason given.

Theoretically there will always be a multitude of individuals that all humans and all apes are descended from. One or more of those will be the most recent.

I wrote to a VERY emininent biologist on the issue, and consider myself lucky to get a reply.I won't post his name of contact incase anyone takes issue with what he says and decides to harass him, but he said...

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Actually, you need to specify what you mean by "most recent
common ancestor". Mitochondrial Eve is simply the one FEMALE
individual from which all mitochondrial DNA came from. But the
genome of an individual is far more than mitochondrial DNA--there is
all that nuclear DNA. Each bit of nuclear DNA has its own most
recent common ancestor, which differs from all the other most recent
common ancestors: the Y-chromosome Adam, for example, lived much
more recently than those individuals who provided other bits of DNA
on other chromosomes. When we biologists talk of "most recent common
ancestors," we are referring to SPECIES; i.e, that species whose
members, in toto, provided all of the ancestral DNA of a descendant.
This is one species that can sometimes be identified, whereas the
MRCA of bits of DNA all differ from each other, and are individuals.

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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.

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"There are three kinds of lies: lies, damned lies, and statistics."

Not to brag, but the reply you got is almost the same as my reply in Post #57. Can I now consider myself an eminent biologist?

Go ahead, but i figured if we got that from a guarenteed reliable source any argument could be taken from there.Basically I was mistaken in thinking every INDIVIDUAL had the same Most recent common ancestor, but every gene has their own individual most recent ancestor.

Could you write more clearly what you mean here. It just doesn't make sense to me. I mean if I just interpret exactly what you said then it doesn't make sense in light of some of what you've already stated before in this thread. Specifically this part: Do you see what I mean? You have harped a few times about a correct understanding of the phrase "most recent common ancestor" and then you make a statement like that. How am I supposed to figure out what it is you're saying there?Edited by CosmicChimp, : wording

your gonna have to be more specific, i dont understand

It looks to me like you're saying that not every individual has the same MRCA. But you've not made it clear in your post three back #112.Edited by CosmicChimp, : No reason given.

Ok no woops I meantWe all have same MRCA's, but they can be multiple individuals. That is what i got from the email the proff sent me.

That seems to be tautological. To rephrase it, you are saying that we have a common ancestor in common.In addition, we do not all share the same MRCA's. Me and my siblings share a very recent common ancestor (our parents) that you do not share with us. The same for you and your siblings, if you have any.For any group of people there will be an ancestor that they all share, and one of those ancestors will be the most recent by definition. However, this MRCA can be different for different groups.And just in case . . . Perhaps this is what you meant to say and I am suffering from a lack of reading comprehension.

He knows that already. The idea that defining the group will point to the MRCA, has also already been pointed out in the thread at least a few times. Defining the group is prerequisite. But your posts are always good, so don't feel criticized.

I happened to watch "Neanerthal Code" on the National Geographic Channel list night and it prompted a question that someone might be able to answer. Don't worry, it relates to the topic.One of the theories that attempts to explain the disappearance of the neanderthals is the assimiliation theory. That is, neanderthals and anatomically modern humans interbred and the neanderthal genes were diluted in the modern human population. If this is so, then shouldn't we be able to find a mitochondrial lineage in the human population? More importantly, could there be a person out there right now that is carrying mitochondria from this neanderthal lineage?The reason I ask this is that the Mitochondrial Eve study was based on a cross section of the human population. Given the technological limits it is understandable that they didn't sequence 3 million mitochondrial genomes to cover just 0.5% of the population. If only 1 in every million people carry neanderthal mitochondria there's a pretty good chance it would have been missed, or so it would seem. Are my concerns unfounded? Am I smoking crack?

No, you are right on the money. That's exactly what geneticists have been looking for to try to determine whether ancient humans interbred with neanderthals. I'm not positive which genes they're looking at, but mt-DNA is always a good one. So far, though, there isn't any evidence of neanderthal genes in the human population. Sure, they may just be so diluted that we just haven't come across them yet, but it's not looking like that's the case. They're currently working on sequencing the neanderthal genome as we speak from some frozen specimens, and hopefully that will make it easier to figure this all out.

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"There are three kinds of lies: lies, damned lies, and statistics."