CurtC
Illuminator
I can see that, but how long ago was this mitochondrial DNA combined with our ancestors'? Do mice have it? Birds? Insects? Could "Eve" have been a troglodyte?
Was there an "Eve"?
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CurtC said:
That was exactly my point, Curt. How much cross-species homology is there?
You know, the "creation apologists" jumped all over this as supporting the theory of Eve, but all the facts may not be known... or reported. If it turns out that the data shows a cross-species homology with, at the very least, mammals or even just chimpanzees, it will kind of blow a hole in their whole "I ain't no monkey's uncle" anti-evolution rhetoric.
-TT
The date generally given for Mitochondrial Eve is around 145000 BP.
Since y chromosomes apparently change faster, the oldest suggested date for an Adam is about 65000BP.
So they were not well acquainted with each other.
I believe the bulk of human mitochondrial DNA will be identical to any mammalian mitochondrial DNA, but there are the usual repeating sections of DNA, much of it non expressed, which vary; as well as a small number of major point mutations, which are characteristic markers for major divergence points. It seems that the mutation rate of MDNA is low by most standards, hence the older date for Eve.
The thing to remember is that Eve was just one member of a widely distributed human population. There was at least one other human species alive then too- the Neanderthals. If we went back maybe another hundred thousand years, there must be one woman who had two daughters, one of whom was on the Neanderthal line , the other on the Hom sap sap line. They were not identical twins, (almost certainly) and may have had different fathers, but they had the same mother, who was just one of a flourishing population of earlier human or hominid.
Go back six million years or so and there was a female who had two daughters, one of whom is ancestral to all female humans and the other of whom is ancestral to all modern female apes.
And SHE was just one in a crowd. There's nothing magical about this.
Since y chromosomes apparently change faster, the oldest suggested date for an Adam is about 65000BP.
So they were not well acquainted with each other.
I believe the bulk of human mitochondrial DNA will be identical to any mammalian mitochondrial DNA, but there are the usual repeating sections of DNA, much of it non expressed, which vary; as well as a small number of major point mutations, which are characteristic markers for major divergence points. It seems that the mutation rate of MDNA is low by most standards, hence the older date for Eve.
The thing to remember is that Eve was just one member of a widely distributed human population. There was at least one other human species alive then too- the Neanderthals. If we went back maybe another hundred thousand years, there must be one woman who had two daughters, one of whom was on the Neanderthal line , the other on the Hom sap sap line. They were not identical twins, (almost certainly) and may have had different fathers, but they had the same mother, who was just one of a flourishing population of earlier human or hominid.
Go back six million years or so and there was a female who had two daughters, one of whom is ancestral to all female humans and the other of whom is ancestral to all modern female apes.
And SHE was just one in a crowd. There's nothing magical about this.
Badger
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As a side comment, I wonder if this mtDNA change is the edge Modern humans needed to edge out Neanderthals. A slight increase in energy efficiency, over tens of thousands of years would be significant in which group survives.
Back to your regular programming.....
Back to your regular programming.....
Soapy Sam said:
I think what's pretty cool about it, though, is that it can help you get your head around the concept of "diverging lines" in ancestries. For instance, there are certain genes that we have now that will be nearly ubiquitous and will, for whatever specific reasons, survive into what will become our far-in-the-future genetic progeny. These may be selected by such things as a unique advantage in a particular disease (such as the few lucky people who seem to be able to bathe in HIV virus and never contract it). That line will eventually be traceable backwards to a common ancestor. The question is how far back can this be traced until we can find the one prototype that first produced or carried that genetic material.
There are already proteins, called "ubiquitins" (originally enough
), that we possess as a fairly common intracellular protein. They serve various functions such as cell architecture and structural support, transport and degradation of other proteins, intracellular buffering, just to name a few. These genes are prevalent all throughout nature, and in many cases there is very little difference between those proteins we have in our cells compared to those in a dog's cell to those in a chicken's cell to even those in a fungal cell. Sometimes there's no difference.So, while it's a neat detective story to pick-out DNA in a mitochondria and trace it back to a single "Eve", I think it's equally interesting to look at the basic components of life - using the entire mitochondria itself, as an example - to show a much longer conjoined history with all species, and as living proof of evolution as a fact, not a theory.
It's very fascinating, at least to me.
-TT
SkepticalScience said:
I believe this is a fatal flaw in the theory. I'll accept that the population must have been smaller, but it would never get smaller than tribes or packs of monkey-men.
So how did they all get the same mitochondrial DNA? Because molecular evolution HEAVILY selects against those that..... suck.
Show me experiments where you replace an organism's mitochondrial DNA with different varieties.... I think you might find that even small mutations and variants would cause chronic problems.
I am thinking, specifically, of un-coupling proteins that were once hoped to be a weightloss solution. Well... long story short, they serve to disrupt the (inner?) mitochondrial membrane and allow protons to rush out into the matrix, ruining the gradient that drives ATPase' production of ATP. (Did I get that right?) My point is that only a minor change in the membrane structure can be lethal. Mice get flush-red hot and die from these drugs.
(Dolly the sheep may be another example... wasn't she sickly because her mitoDNA was screwed up?)
This all serves as an argument for directed evolution, an idea many biologists abhor. My belief is that molecular constraints limit the phenotypic design and construction of mitochondria, and therefore only a small number of variants are possible. (This is like saying that DNA evolved to be a double-helix, because it is the best structure that's capable of what it does..... to which I say DUH!)
Dragon
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I've just got Richard Dawkin's latest book "The Ancestor's Tale" which covers this topic beautifully. I've not got it with me at the moment, but when I get home I'll post a couple of extracts.
Oh, and Soapy -
back at ya!
CurtC - Mitochondrial Eve was human.
Oh, and Soapy -
back at ya!CurtC - Mitochondrial Eve was human.
SkepticalScience
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Great Dragon!
Please Post. . .I didn't even realize Dawkins had a new book!
Please Post. . .I didn't even realize Dawkins had a new book!
Walter Wayne
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Did this woman have more than one father? If not we can also all say we are all descended from one male as well.
Since we all have one male and one female parent (for now) if you can trace all human ancestry back to one individual than there must be one "father of humanity" and one "mother of humanity", that individuals father and mother.
Mithocondrial DNA may proove an eve, but it then by definition prooves an adam. Not really relevant, but I find it interested that after the mtDNA studies people continue only refer to the "eve" individual and rarely the adam.
Walt
Since we all have one male and one female parent (for now) if you can trace all human ancestry back to one individual than there must be one "father of humanity" and one "mother of humanity", that individuals father and mother.
Mithocondrial DNA may proove an eve, but it then by definition prooves an adam. Not really relevant, but I find it interested that after the mtDNA studies people continue only refer to the "eve" individual and rarely the adam.
Walt
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Walter Wayne said:
There is a Y-chromosome Adam, though he may be separated centuries in time and thousands of miles in space from Eve.
Dragon- I'm reading "The Ancestor's Tale" as well. I suspect I will not make it all the way though- it is more of a reference book than most of Dawkins' popular science publications.There's a huge amount of data in there.
Third Twin- Fascinating, I agree. Dawkins makes the valid point though, that while tracking MDNA is fascinating and valuable, we must remember that this MDNA exists in the bodies of individuals who have inherited other genes from many different sources. He even points out that some of their lineal ancestors may have contributed no genetic component whatever to their living descendants after enough time has passed to permit real sexual "dilution" of genes. In short ,we must bear in mind that genes move around, recombine and follow quite different lines of descent from the individual creatures ("vehicles" in his terminology) which carry them.
A brief quote:- "...it is important to understand that Adam and Eve are only two out of a multitude of [Most Recent Common Ancestors] that we could reach if we traced our way back through different lines.They are the special-case common ancestors that we reach if we travel up the family tree from mother to mother to mother, or father to father to father respectively. But there are many, many other ways of going up the family tree: mother to father to father to mother, mother to mother to father to father , and so forth. Each of these possible pathways will have a different MRCA. "
-Dawkins.R., pp49, 'The Ancestor's Tale', Weidenfeld & Nicolson . ISBN 0-297-82503-8
Third Twin- Fascinating, I agree. Dawkins makes the valid point though, that while tracking MDNA is fascinating and valuable, we must remember that this MDNA exists in the bodies of individuals who have inherited other genes from many different sources. He even points out that some of their lineal ancestors may have contributed no genetic component whatever to their living descendants after enough time has passed to permit real sexual "dilution" of genes. In short ,we must bear in mind that genes move around, recombine and follow quite different lines of descent from the individual creatures ("vehicles" in his terminology) which carry them.
A brief quote:- "...it is important to understand that Adam and Eve are only two out of a multitude of [Most Recent Common Ancestors] that we could reach if we traced our way back through different lines.They are the special-case common ancestors that we reach if we travel up the family tree from mother to mother to mother, or father to father to father respectively. But there are many, many other ways of going up the family tree: mother to father to father to mother, mother to mother to father to father , and so forth. Each of these possible pathways will have a different MRCA. "
-Dawkins.R., pp49, 'The Ancestor's Tale', Weidenfeld & Nicolson . ISBN 0-297-82503-8
Well, to be absolutely accurate (and a nitpicking arse) about it...Dragon said:
Every human being that has been tested is the mtDNA descendent of a single woman.
All the other lines failed to produce daughters at some point. Could it have been a mtDNA mutation that gave an edge? It's a possibility, but it is not neccessary.
Walter Wayne said:
WW-
You're perhaps giving "Eve" too much credit in the fidelity department.
Since this link is only being tracked through mitochondrial DNA, and mitochondrial DNA can only be passed from the mother to offspring, there's nothing to say that Eve might not have had many male partners that produced separate progeny, all of whom subsequently got her mtDNA, regardless of who provided the sex-determining chromosome (i.e., the father(s)). Tracking all mtDNA back to one "Eve" would not, based on the genetics used in this study, mutually include a single father to make this mtDNA theory valid.
In other words, "Eve" may actually have been somewhat of a trollop. At least, this theory can't exclude that possibility.
-TT
And while we may all get our MDNA from Eve, it's very likely we get our eye colour from that slut Lydia in the next cave, and our wavy hair from Sara down river (who was no better than she had to be).
If we start with a dozen people and track one genetic characteristic, they will all converge in one individual sooner or later. WithMDNA we pick one trait which can be proven to be found in all living humans and which can be traced back to one human individual.
If we chose a different trait, it would converge on a different person, or creature, at a different time. If we chose stereoscopic vision for example, we would have to go back about 70 million years to find the individual it all started with. (It would be impolite to comment upon his paws and whiskers).
If we start with a dozen people and track one genetic characteristic, they will all converge in one individual sooner or later. WithMDNA we pick one trait which can be proven to be found in all living humans and which can be traced back to one human individual.
If we chose a different trait, it would converge on a different person, or creature, at a different time. If we chose stereoscopic vision for example, we would have to go back about 70 million years to find the individual it all started with. (It would be impolite to comment upon his paws and whiskers).
Walter Wayne
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When I say a contempary Adam, I am not implying a husband but a father. True, he didn't have had the mtDNA in question, but mtDNA Eve's parents can also claim the title of Adam and Eve.ThirdTwin said:
Walt