Kurieuo wrote:neo-x wrote:By Couple I meant Mito Eve and Adam, but not them as a couple but rather a couple of Mito Ancestors. That's the point, the Mito DNA is not the only one we have, its the only one which is unbroken yet, mind you that is the DNA we are talking about, as it doesn't point to one individual. Other women from mito eve's times have descendants alive today. Not only that, we also know that Mito-eve as a person is not fixed, whenever one of the two most ancient branch lines dies out, the MRCA will move to a more recent female ancestor.
So we don't only have mito eve's dna, we have other dna as well, which clearly shows more than a single couple which populated the earth.
Openly, I'm confused by your words.
Mito Eve is said to be the common ancestor for all modern
homo sapien saipens women alive today. Based on recent study estimates, Mito Eve is essentially placed at around 100-125k years ago. Right?
So then, what are you meaning when you say that the MDNA is not the only one we have? To me, a Mito Eve and Y-Chrom Adam evidences, although not necessarily so, that modern human woman came through one female ancestor and Y-Chrom Adam that modern human men came via one male ancestor. At least, that is what the evidence would suggest as we have it.
To say otherwise, is to well, do away with an "Eve" and "Adam" concept as science uses them (not in Biblical terms, but it Mito Eve and Y-Chromo Adam terms).
But, I never heard science talking of Miti Eve
s and Y-Chrom Adam
s (plural). Yes, perhaps there were others whose lines were not carried down, but to declare there were many lineages to
homo sapiens sapiens rather than a couple is just as speculative a believing in one couple (much more-so imo).
It is actually very simple but perhaps is misunderstood. When we say Mito Eve, we don't mean a fixed individual in history. The important thing to note is the mtDNA is the highlight here, not the person. The ironic name makes it confusing I guess.
quoting here from wikipedia just to save time,
One misconception surrounding mitochondrial Eve is that since all women alive today descended in a direct unbroken female line from her, she must have been the only woman alive at the time. However, nuclear DNA studies indicate that the size of the ancient human population never dropped below tens of thousands. Other women living during Eve's time have descendants alive today, but at some point in the past each of their lines of descent did not produce a female who reproduced, thereby breaking the mitochondrial DNA lines of descent.
*****
The definition of mitochondrial Eve is fixed, but the person in prehistory who will fit this definition can change, not only because of new discoveries, but also because of unbroken mother-daughter lines coming to an end by chance. It follows from the definition of Mitochondrial Eve that she had at least two daughters who both have unbroken female lineages that have survived to the present day. In every generation mitochondrial lineages end – when a woman with unique mtDNA dies with no daughters. When the mitochondrial lineages of daughters of mitochondrial Eve die out, then the title of "Mitochondrial Eve" shifts forward from the remaining daughter through her matrilineal descendants, until the first descendant is reached who had at least two daughters who both have living, matrilineal descendants. Once a lineage has died out it is irretrievably lost and this mechanism can thus only shift the title of "Mitochondrial Eve" forward in time.
We also know that this Mito eve, had a mother too. That she was not taken out of Adam as the biblical story says. But to move the point forward, if a woman produces only male offspring, her mtDNA won't be passed along, since children don’t receive mtDNA from their father. This means that while the woman’s sons will have her mtDNA, her grandchildren won’t, and her line will be lost. But that doesn't mean that she doesn't have descendants today, she only doesn't have female descendants.
Many women alive at the same time as Mitochondrial Eve but many of them have descendants alive today. They may have left descendants via either son or daughters (and grandsons or granddaughters, and so on).
Nuclear genes from these contemporary women of Mitochondrial Eve are present in today's population, but mitochondrial DNA from them is not.
What distinguishes Mitochondrial Eve (and her matrilineal ancestors) from all her female contemporaries is that she has a purely matrilineal line of descent to all humans alive today, whereas all her female contemporaries with descendants alive today have at least one male in every line of descent. Because mitochondrial DNA is only passed through matrilineal descent, all humans alive today have mitochondrial DNA that is traceable back to Mitochondrial Eve.
Please note, Mitochondrial Eve is the most recent common ancestor (MRCA) of all humans via the mitochondrial DNA pathway,
not the unqualified MRCA of all humanity. All living humans can trace their ancestry back to the MRCA via at least one of their parents, but Mitochondrial Eve is defined via the maternal line. Therefore, she necessarily lived at least as long, though likely much longer, ago than the MRCA of all humanity.
The existence of Mitochondrial Eve and Y-chromosomal Adam does not imply the existence of population bottlenecks or a first couple. They each lived within a large human population at a different time. Mitochondrial Eve is one of the many common ancestors we can trace back to via different gene pathways., If we pick a different gene, we will get to a different MCRA.
EDIT
I think what may be confusing is that we understand DNA as only nuclear DNA, which is the building block of life. However we don't have mito eve's nuclear dna, so therefore when we say we all share her dna we are talking about mitchondrial dna,
for quick reference please see
Nuclear DNA and mitochondrial DNA differ in many ways, starting with location and structure. Nuclear DNA is located within the nucleus of eukaryote cells and usually has two copies per cell while mitochondrial DNA is located in the mitochondria and contains 100-1,000 copies per cell. The structure of nuclear DNA chromosomes is linear with open ends and includes 46 chromosomes containing 3 billion nucleotides. Mitochondrial DNA chromosomes have closed, circular structures, and contain 16,569 nucleotides. Nuclear DNA is diploid, inheriting the DNA from both mother and father, while mitochondrial DNA is haploid, coming only from the mother. The mutation rate for nuclear DNA is less than 0.3% while that of mitochondrial DNA is generally higher.[5]
So now can you see with respect to what I wrote earlier, that we have other mitochondrial Dna's too, its just that only one of them is unbroken in women. That is, some contemporaries of the MRCA are ancestors of no one in the current population. The rest of the contemporaries of the MRCA may claim ancestry over a subset of current population, but not the entirety of current population.
mitochondrial Eve is not the mother of all humanity, she is the most recent mother of all living humanity. A side affect of this is that the individual who was mitochondrial Eve changes over time, due to coalescence.
The idea of coalescence is fairly straightforward. Every human has parents. However, not every human has kids. The number of people who were alive 100 years ago who have living descendants is only a fraction of the people who were actually alive 100 years ago. As we go back in time, the number of people who were alive at that time who have living descendants keeps decreasing, until there is a single person from whom every living person descends.
We call this individual the most recent common ancestor (MRCA). That individual also had parents, and grandparents, and great-grandparents etc, and all of humanity shares descent from those individuals as well. However, they are not the “most recent” common ancestors, but merely common ancestors, and are not very informative for evolutionary study. As time goes on, the current MRCA will become merely another common ancestor, and the new MRCA will become one of its descendants.
In a few hundred thousand years, the MRCA for all individuals alive may very well be someone who is alive right now. I hope that clarifies it further.