As you may have already noticed I have been into evolution and that sort of readings in the past couple of weeks (as aparant from my book list).
I was just reading "River Out Of Eden"by Richard Dawkins and came across some amazing stuff that (as usual) I cannot resist sharing with you ;)
Let me quote straight from the book. At the end of one of the chapters he says:
"We may come to the following conclusions:
First, it is necessarily certain that there existed on female who we may call Mitochondrial Eve who is the most recent common ancestor of all modern humans down the female only pathway.
Second, It is also certain that there existed only one person of unknown sex who we may call the Focal Ancestor who is the most recent common ancestor of all modern humans down any pathway.
Third, although it is possible that the Mitochondrial Eve and the Focal Ancestor are one and the same it is vanishingly unlikely that this is so.
Forth, it is somewhat more likely that the Focal Ancestor was a male than a female.
Fifth, Mitochondrial Eve very probably lived less than a quarter of a million years ago.
Sixth, there is disagreenment where Mitochondrial Eve lived but the balance of informed opinion still favours Africa."
OK, if you do not have much previous knowledge in this field of science lets elaborate a little bit using (as usual) Wikipedia.
What or Who is the so-called Mitochondrial Eve?Mitochondrial Eve a.k.a (mt-mrca) is the name given by researchers to the woman who is defined as
the matrilineal most recent common ancestor (MRCA) for all currently living humans. Passed down from mother to offspring, her
mitochondrial DNA (mtDNA) is now found in all living humans: every mtDNA in every living person is derived from hers.
Mitochondrial Eve is the female counterpart of Y-chromosomal Adam, the patrilineal most recent common ancestor, although they lived at different times.
She is believed to have lived about 140,000 years ago in what is now Ethiopia, Kenya or Tanzania. [citation needed] The time she lived is calculated based on the molecular clock technique of correlating elapsed time with observed genetic drift.
Mitochondrial Eve is the 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.
Please read this carefully cuz it may not be apparent at first:The existence of Mitochondrial Eve and Y-chromosomal Adam does not imply the existence of population bottlenecks or a first couple. They each may have lived within a large human population at a different time.
What is Mitochondrial DNA?Mitochondrial DNA (mtDNA) is the DNA located in organelles called mitochondria. Most other DNA present in eukaryotic organisms is found in the cell nucleus.
Stress on this part:
Nuclear and mitochondrial DNA are thought to be of separate evolutionary origin, with the mtDNA being derived from the circular genomes of the bacteria that were engulfed by the early ancestors of today's eukaryotic cells. I bet you did not know that!!! Did you???
Each mitochondrion is estimated to contain 2-10 mtDNA copies. In the cells of extant organisms, the vast majority of the proteins present in the mitochondria (numbering approximately 1500 different types in mammals) are coded for by nuclear DNA, but the genes for some of them, if not most, are thought to have originally been of bacterial origin, having since been transferred to the eukaryotic nucleus during evolution.
If you studied molecular biology you should already know this:In most multicellular organisms, mtDNA is inherited from the mother (maternally inherited).
What amased me was the the mechanism of this:Mechanisms for this include simple dilution (an egg contains 100,000 to 1,000,000 mtDNA molecules, whereas a sperm contains only 100 to 1000), degradation of sperm mtDNA in the fertilized egg, and, at least in a few organisms, failure of sperm mtDNA to enter the egg. Whatever the mechanism, this single parent (uniparental) pattern of mtDNA inheritance is found in most animals, most plants and in fungi as well.
Mutations in mtDNA can in some cases cause maternally inherited diseases and some evidence suggests that they might be major contributors to the aging process and age-associated pathologies. [citation needed] In humans (and probably in metazoans in general), 100-10,000 separate copies of mtDNA are usually present per cell (egg and sperm cells are exceptions). In mammals, each circular mtDNA molecule consists of 15,000-17,000 base pairs, which encode the same 37 genes: 13 for proteins (polypeptides), 22 for transfer RNA (tRNA) and one each for the small and large subunits of ribosomal RNA (rRNA).
Some misconceptions:Mitochondrial Eve is the most recent common
matrilineal ancestor, not the MRCA of all humans. The MRCA's offspring have led to all living humans via sons and daughters,
but Mitochondrial Eve must be traced only through female lineages, so she is estimated to have lived much longer ago than the MRCA. According to probabilistic studies, Mitochondrial Eve is thought to have lived around 140,000 years ago.
I believe this is an important point to make:Allan Wilson's naming
Mitochondrial Eve after
Eve of the Genesis creation story has led to some
misunderstandings among the general public. A common misconception is that Mitochondrial Eve was the only living human female of her time. Had this been the case, humanity would have long since become extinct due to an extreme example of a population bottleneck. Indeed, not only were many women alive at the same time as Mitochondrial Eve but many of them have living descendants through their sons. While the mtDNA of these women are not as common as the MRCA, their Nuclear genes are present in today's population.
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Did you know all of this? Are you interested in such topics? Please leave a comment :-)Photo credit:
Canadacow - Creative Commons
