Mitochondrial Eve

Zombrex

Tim Robbins wrote: »

But my question is specific, is it logically possible for the MRCFA for the human species not to be a human? It seems to me it is, but it is evidence and theory which suggest it is not.

Well the MRCFA changes from time to time based on the current population, so it is logically possible that it is anyone.

The current one probably was a human based on the time scale.

Zombrex

Rev Hellfire wrote: »

I'm sure I'm missing something important here but it is just degree's of bacon we're talking about. We are not talking about a common singular ancestor for everyone, but rather the most common one (ie. highest bacon factor) ?
I mean its cool in a that's cool sort of way but beyond that how ? Bear with me I'm stupid.

The most recent common ancestor (an ancestor shared by all living humans) was alive approx 3,000 years ago.

What Eve is is the most recent common anscestor on the material line, so mother's mother's .... mother's mother

Because of that you need to go back much much further than the most recent common ancestor.

It is not really the 6 degress of seperation thing, though that shares similar mathematical properties.

Rev Hellfire

But Mitochondrial Eve is not a fix entity it can and does shift, the most obvious one is the Mitochondrial Eve of the our current Mitochondrial Eve, who may herself get usurped by another.

All it is a genetic game with the same rules as degree's of bacon. My under standing of it is she is not the common ancestor of all humans alive today, but rather the one to which the largest number of people can link back to.

I guess we'll have to wait until robin gets to talk to someone who actually knows and works in the relevant field to get the true low down.

Zombrex

Rev Hellfire wrote: »

But Mitochondrial Eve is not a fix entity it can and does shift, the most obvious one is the Mitochondrial Eve of the our current Mitochondrial Eve, who may herself get usurped by another.

Yes

Rev Hellfire wrote: »

All it is a genetic game with the same rules as degree's of bacon.

Well the degree's of bacon game you have to work if you know someone who knows someone who knows someone etc etc who knows Kevin Bacon. So it isn't exactly the same :-)

As you say the Mit Eve can shift around over the generations.

Rev Hellfire wrote: »

My under standing of it is she is not the common ancestor of all humans alive today, but rather the one to which the largest number of people can link back to.

No she is the common ancestor of all females alive today. There are other more recent common ancestors of a large number of females alive today, but to find the woman that every woman on Earth through the material lineage you need to go back 140,000 years. That is because you can't have a daughter-son-daughter link, it has to be daughter-daughter-daughter all the way back.

On the other hand the common ancestor of all humans lived only 3,000 years ago. That is because you can have daughter-son-daughter chain, so you don't need to go back as far.

pH

Rev Hellfire wrote: »

But Mitochondrial Eve is not a fix entity it can and does shift, the most obvious one is the Mitochondrial Eve of the our current Mitochondrial Eve, who may herself get usurped by another.

All it is a genetic game with the same rules as degree's of bacon. My under standing of it is she is not the common ancestor of all humans alive today, but rather the one to which the largest number of people can link back to.

Not sure it really matters, but it's not "the largest number", it's "all people can link back to on their maternal line". She is the Mitochondrial DNA Most Recent Common Ancestor, so she is not the most recent common ancestor (he or she is thought to have lived about 3,000 years ago) but is definitely a common ancestor (the most recent by maternal descent).

As for her importance or otherwise, you're correct it's just a term, she existed, and locating here in time/place is a challenge to which people have risen.

Wicknight wrote:

No she is the common ancestor of all females alive today.

No she is the most recent ancestor on the maternal line of everyone (male and female) alive today.

sdep

I'll throw in 'coalescent theory', which models this. It's an application of population genetics that models how, going back through generations, all current copies of a gene coalesce to a single common ancestor.

Going in the forwards direction, starting in mtEve's generation, you get sampling effects occurring in each generation, as not every female has offspring - or more specifically female offspring who will continue her line. As time rolls on, the population has fewer and fewer matrilines from the starting generation. Eventually you reach a point where only one is present - mtEve's.

Of course, the 'starting generation' mentioned above is nothing special. Every generation has its own mtEve, so in Eve's own generation the MRCFA would have dated to much earlier, and as time progressed, the MRCFA of each generation will have dated more and more recently.

As to mtEve being human, that's just a consequence of figuring out when she lived, looking at fossils from around then and deciding if they were human or not.

Applying the same method to human and Neanderthal mtDNA sequences gives a much older MRCFA, of the order of 750,000 years, so non-human.

Rev Hellfire

So hows does paternal mtDNA effect the concept of the Mitochondrial Eve, or does it at all ?

Johnmb

Rev Hellfire wrote: »

So hows does paternal mtDNA effect the concept of the Mitochondrial Eve, or does it at all ?

It doesn't effect the concept. You get your mtDNA from your mother, so there is no paternal mtDNA to trace back. You get the Y-chromosome from your father, and that is what is traced back along the paternal line (father's father's father's......father). He dates to about 60,000 year ago if I remember correctly, and is referred to as Y-Chromosomal Adam.

Rev Hellfire

Johnmb wrote: »

It doesn't effect the concept. You get your mtDNA from your mother, so there is no paternal mtDNA to trace back. You get the Y-chromosome from your father, and that is what is traced back along the paternal line (father's father's father's......father). He dates to about 60,000 year ago if I remember correctly, and is referred to as Y-Chromosomal Adam.

As far as I'm aware there is evidence of paternal mtDNA been passed on, so this must have some bearing on the eve theory since its basic idea was that it can only be passed on the female line.

Johnmb

Rev Hellfire wrote: »

As far as I'm aware there is evidence of paternal mtDNA been passed on, so this must have some bearing on the eve theory since its basic idea was that it can only be passed on the female line.

All mtDNA actually passed on seems to be from the mother. There is a theoretical possibility that up to 0.1% could come from the father, but that is a theoretical maximum and, as far as I know, has never been observed in reality.

Zombrex

pH wrote: »

No she is the most recent ancestor on the maternal line of everyone (male and female) alive today.

That is a good point, the current generation the males are also included, everyone after all has a mother.

Rev Hellfire

Johnmb wrote: »

All mtDNA actually passed on seems to be from the mother. There is a theoretical possibility that up to 0.1% could come from the father, but that is a theoretical maximum and, as far as I know, has never been observed in reality.

There are a good few articles on the subject of paternal mtDNA and recombination on nature.com along with links to the relevant studies, so its not exactly a theoretical possibility. I'm not saying that it rules out the existence of an eve, but it does muddy the pool somewhat.

Johnmb

Rev Hellfire wrote: »

There are a good few articles on the subject of paternal mtDNA and recombination on nature.com along with links to the relevant studies, so its not exactly a theoretical possibility. I'm not saying that it rules out the existence of an eve, but it does muddy the pool somewhat.

Not really. The amount in minuscule, and even if you have a tiny bit of mtDNA from your father, he got it from his mother, and she from her mother etc, bringing you back into the female line. The chances of having a line of people where the males passed on their maximum amount (0.1%) of mtDNA consistently enough to effect Eve is so slim as to be statistically unimportant.

Zillah

Rev Hellfire wrote: »

I'm asking why you think such an entity is important. What does its existence actually prove. For example its certainly not the origin of Homo Sapien.

Don't you think its cool that there was a single woman who's offspring would eventually take over the planet?

Imagine her, a couple hundred thousand years ago. There's probably only a few tens of thousands of humans alive across the whole globe. She lives in a small travelling tribe of perhaps fifty people. That one woman is the mother of every human being on the planet today.

I think thats cool.

Rev Hellfire

Ohh I agree its cool, but what's the practical benefit of it ?

Johnmb

Rev Hellfire wrote: »

Ohh I agree its cool, but what's the practical benefit of it ?

Eve isn't particularly important. Finding her is just a side effect of the study. The practical benefit of the study is to trace human ancestry.

bleg

http://en.wikipedia.org/wiki/Mitochondrial_eve

sdep

Rev Hellfire wrote: »

There are a good few articles on the subject of paternal mtDNA and recombination on nature.com along with links to the relevant studies, so its not exactly a theoretical possibility. I'm not saying that it rules out the existence of an eve, but it does muddy the pool somewhat.

Initial evidence was indirect - looking for the tell-tale traces left by recombination - splicing between different versions of the mtDNA sequence that had to be present together in the cell. People challenged this indirect evidence, but it wasn't demolished.

More recently, a patient apparently inherited a mitochondrial disease from his father, and about 90% of mitochondria in his muscle tissue turned out to be paternal. Apart from this case, though, direct sequencing methods show paternal inheritance to be very rare. Paternal mitochondria are swamped by maternal ones in the fertilised egg, and they're also selectively destroyed. A breakdown of this elimination might mean more paternal mitochondria survive.

So many things have to happen to get inheritance of paternal-maternal recombinant mitochondria. The father's mitochondria have to get into the egg, survive there, not get diluted out in subsequent cell divisions, fuse with and recombine their DNA with the maternal mitochondria, get into the germline for the next generation, all in a woman, who has to have children (ideally daughters). So things are stacked against it.

Alternative possibilities are recombination with mitochondrial genes that have transferred over evolutionary time into the 'conventional' nuclear genome (though there are similar problems with this) or, more likely, recombination between different maternal mtDNA molecules inherited from the same egg.

What does all this mean for mtDNA Eve?

Well, the link between matrilineal Eve and the most recent mtDNA ancestor would be broken. Go back far enough and there'll still be a single matrilineal ancestor, but her line won't be perfectly associated with the mitochondrial DNA molecule. The date at which the most recent common mtDNA ancestor lived will change; most authors suggest a more ancient date. More significantly than Eve herself, some of the mtDNA-inferred dates of human population origin, expansion and migration might have to be reassessed. I wouldn't expect the dates to change too radically though.

Rev Hellfire

bleg wrote: »

http://en.wikipedia.org/wiki/Mitochondrial_eve

Lets all link to our favorite school year book

Akrasia

cavedave wrote: »

Just some biology points.
1. Very little mitocondria comes from the male so there is really no mitocondrial Adam. A Y-chromosome Adam there is.

2. Two different species cannot interbreed and have fertile offspring. So a horse and donkeys child cannot have children itself (except in rare cases). This means that man was not half homo erectus half homo sapien.

Correct me if i am wrong

There was one divergent colony/family of homo erectus where due to a mutation and natural selection, over a few generations of interbreeding, the genetic differences became so great that this colony could no longer breed with homo erectus and became homo sapien. That was colony zero of humanity.

There were probably lots of other similar divergent mutations over time that were unsuccessful and died out.