Mitochondria evolution questions

[Liberal]

This might end up in Great Debates, but then again, there might be some straightforward answers that I just overlooked. I’m having a hard time understanding the argument made by Charles Weber on this webpage. A few specific questions, please.

If a woman had a mutation among her mitochondria which gave her a significant advantage, that mitochondria would spread throughout her village.

That is so amphibolous that it’s meaningless, unless I misunderstand altogether. Why would a mere advantage, I guess in adaptation, guarantee that her mitochondria would “spread throughout her village”? Is there some sort of contagion involved?

If a gene arose, for instance, which enabled an “Eve” to average 10 babies in an average lifetime while all other non “eves” were averaging 9, that gene and its mitochondria associates would relentlessly supplant all others.

Well, maybe. But as the author goes on to say, this would take a long time and could be nullified by any number of accidents and circumstances. Is the gene he speaks of now an additional gene to the one above? The one above seems to be a gene that eases the survival of Eve herself, while this one seems to be a gene that endangers her survival (assuming that every child birth in those days was fraught with danger both to the mother and the child).

Even if a single woman was captured or seduced by a Neanderthal man in a local population of 10,000 Neanderthals, eventually “eve’s” mitochondria would virtually exclude all others if it were not accidentally eliminated early on and much, much before 200,000 years.

Why? He says something about the energy output. How does that apply?

Barring a drastic unknown difference in any of the above parameters in ancient times, it is safe to say that [one?] single family could not possibly have been responsible for all the present day nuclear gene variety in only 200,000 years. Even 2,000,000 years is dubious.

If you read the paragraph, peppered by impressive bibliographical references, that contains that sentence, he makes a compelling case for the assertion. But what is he saying? That there was not one Eve, but many? If so, did the same gene(s) spontaneously mutate at the same time? Was there something in the climate?

Please help me understand this. Thanks.

[KarlGrenze]

Maybe by village they mean descendants…if one of Eve’s mitochondrial genes changed, and the changed went to the mitochondria of her eggs…then yes, all her descendants would have that gene…people only inherit the mitochondrias from their mothers, since it is the former cell structure of the egg that gives rise to the zygote, or fertilized egg and future embryo.

[KarlGrenze]

Originally posted by Libertarian *
**
Well, maybe. But as the author goes on to say, this would take a long time and could be nullified by any number of accidents and circumstances. Is the gene he speaks of now an additional gene to the one above? The one above seems to be a gene that eases the survival of Eve herself, while this one seems to be a gene that endangers her survival (assuming that every child birth in those days was fraught with danger both to the mother and the child).*

I agree, unless he forgot to add succesfully has 10 pregnancies…meaning that she was more resistant and could give childbirth easily and with less complications than others…but childbirth is not independant only on good-birthing-genes, so I don’t understand that.

Originally posted by Libertarian**

If you read the paragraph, peppered by impressive bibliographical references, that contains that sentence, he makes a compelling case for the assertion. But what is he saying? That there was not one Eve, but many? If so, did the same gene(s) spontaneously mutate at the same time? Was there something in the climate?

Please help me understand this. Thanks. **

The genetic variations in mitochondria, which is only inherited thru the mother, is too great to assume that just one Eve (one female ancestor) existed. Mutations are rare and take time. What he may mean is that there were first a group of “Eves”, that later on had mutations and passed them on to their children, and again that their daughters had more mutations and passed them on. I hope I helped something…

[Revtim]

*Originally posted by Libertarian *
Why? He says something about the energy output. How does that apply?

IIRC, the mitochondria are the cell’s power plants, so pretty much the only type of advantage that could come from a beneficial mutation of the mitochondria would be more efficient use of fuel.

[Tars_Tarkas]

The mitochondriaare the power plants. Here is an animation of electron transfer in mitochondria. Here is an animation of ATP synthesis in mitochondria.

The mitochondria creates ATP (adenosine triphosphate)(hereis anohter animation of ATP synthesis)which is used by our cells as energy. More efficient energy production means less time gathering food and more time making babies. Like **KarlGrenze
** said, we only inherit mitochondria from our mothers, so it follows that more efficient mothers would make more better babies.

[Tars_Tarkas]

Doh! forgot to answer the last part! He seems to be saying that the mutation rate in mitochondria is too low to account for the genetic diversity apparent in humans to be from just one Eve and it is likely that several different mitochondrial mutations appeared from different sources. I am not sure at what exactly he is getting at by eliminating several theories. He does seem to ignore the theory i follow more than others in that humans interbreeded with the other apes as well as wiping them out. This can account for some of the genetic diversity in places where there shouldn’t be (but not all, IIRC). Thre is also a theory that humans evolved in several places simultaneously, which may factor in some diversity as well. Overall, humans are not very diverse at all with up to 99.9%of the same DNA between indiviuals (I study SNPs, Single Nucleotide Polymorphisms, where the basepair differences are between people in DNA. There are about 3 million known SNP sites, and 3 billion basepairs in our genome, so that translates.)