Question about evolution, genetic bottlenecks, and inbreeding

You're absolutely correct. That was my mistake there. I was thinking of common ancestors, not most recent.Edited by Taz, : No reason given.

And I've been saying since the beginning that I'm not denying there could have been only 1 MRCA. I've been trying to point out to you 2 problems with assuming 1 individual MRCA. (1) Having 1 individual MRCA drastically limits the genetic variation in the gene pool. A single disease could potentially wipe out the african cheetah population because of this. (2) On a species scale (such as human and chimp), 1 individual MRCA that connects the two species is a pointless concept. This is not the movie Underworld where lycans and vampires had a common ancestor name Alexander Corvinus.

Why would the two central pairs in the 3rd generation be MRCAs for the 4th generation regardless of whether they moved to islands? The 2 central pairs of generation 3 contribute NO genetic material to either S or Z, therefore they can't be an MRCA for the 4th generation.Though, it's true in that diagram, because of all the inbreeding A-H have equal status as MRCA for S-Z. But, as soon as you start having people mate with individuals not directly descended from the A-H group, that would change.Edited by Stagamancer, : No reason given.

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

Yes but Stag. AS soon as the 4th generation start to breed, both 3rd generation pairs become the common ancestor to at the very latest generation 6 of all the creatures, even though they have split in two and will take two seperate paths. So both species will become 2 different ones, yet have 4 MRCA'sEdited by harry, : No reason given.

Taz, you envisioned this as being one man on a 20 woman island though, which i am jsut pointing out as unneccessary.

Actually, I'd beg to differ on this point. I just came up with this, so hear me out. According to the A-H, S-Z diagram, the 1st generation all have MRCA status BECAUSE of the inbreeding. The less inbreeding there is, the fewer numbers of MRCAs there can be. That is to say, if you only have 1 single individual or pair that is the MRCA for one group, that means their family trees all only touch at that one point. However, if you have multiple MRCAs for a group, that means their genealogies touch multiple times, meaning they are actually more related. I would predict, based on this that while the current Cheetah population has a very low numbers of PROGENITORS (thus the inbreeding problem) they probably have a high number of MRCAs

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

OK, yes. And unfortunately, I must concede that there is no logical inevitability for there always being 1 individual or mating pair that is the MRCA. 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.Edited by Stagamancer, : No reason given.

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

For now, ignore everything I said in this thread. Thanks for confusing the hell out of me now. I'll come back to this once my mind is untangled! That or I don't die first of concussion.Edited by Taz, : No reason given.

great, so when i say it, its trying to find a way to introduce creationism.When staga says it, its reasonable.

What, I can't have doubts about my own understanding of things?Added by edit.Don't get me wrong, I still say it's kinda pointless to look for a single individual most recent common ancestor that connects chimps and humans. To me, this is like trying to find that one specific footprint of yours when you put your foot down the wrong way somewhere in Nevada after you've spent 2 years walking from California to New York.I've become confused about another part of our conversation.Edited by Taz, : No reason given.

They may converge on one person, but they also have ancestors that are not common to both, ancestors that predate the MRCA. For every MRCA there are also many ancestors that are not common to everyone. There were women alive during Mitochondrial Eve's lifetime, and it is very probable that people today carry genes from those women. The same for Y Adam.

I don't think anyone has argued differently.

Haha, I just noticed this post. From your message 26.

quote:

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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.

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I take it you think women are insignificant enough that they don't need a mention?Haha, ok that was a joke. But you should know what I mean. It takes 2 to tango. I don't know why you keep insisting on 1 organism being the Abraham figure.

We don't know. You don't know. 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. 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. No, you find people saying that we need not have only one MRCA. We don't know. And we have absolutely no way of finding out.Does that answer help you to "whittle down the possibilities"?

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.