Editing Mitochondrial Eve (section)

==Female and mitochondrial ancestry==

{{main|Macro-haplogroup L (mtDNA)}}
{{further|Genetic genealogy (matrilineal)|Mitochondrial DNA|Human mitochondrial molecular clock}}

[[File:MtDNA-MRCA-generations-Evolution.svg|thumb|left|200px|Through [[Genetic drift|random drift]] or selection the female lineage will trace back to a single female, such as Mitochondrial Eve. In this example over five generations colors represent extinct matrilineal lines and black the matrilineal line descended from mtDNA MRCA.]]

Without a DNA sample, it is not possible to reconstruct the complete genetic makeup ([[genome]]) of any individual who died very long ago. By analysing descendants' DNA, however, parts of ancestral genomes are estimated by scientists. Mitochondrial DNA (mtDNA, the DNA located in [[mitochondrion|mitochondria]], different from the [[Nuclear DNA|DNA in the nucleus]] of a cell) and Y-chromosome DNA are commonly used to trace ancestry in this manner. mtDNA is generally passed un-mixed from mothers to children of both sexes, along the maternal line, or [[matrilineally]].<ref>{{cite journal |vauthors=Giles RE, Blanc H, Cann HM, Wallace DC |title=Maternal inheritance of human mitochondrial DNA |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=77 |issue=11 |pages=6715–6719 |date=November 1980 |pmid=6256757 |pmc=350359 |doi=10.1073/pnas.77.11.6715 |doi-access=free |bibcode=1980PNAS...77.6715G }}</ref><ref>{{cite journal |vauthors=Birky CW |title=Uniparental inheritance of organelle genes |journal=Current Biology |volume=18 |issue=16 |pages=R692–R695 |date=August 2008 |pmid=18727899 |doi=10.1016/j.cub.2008.06.049 |s2cid=9866662 |doi-access=free }}</ref> Matrilineal descent goes back through mothers, to their mothers, until all female lineages converge.

Branches are identified by one or more unique markers which give a mitochondrial "DNA signature" or "[[haplotype]]" (e.g. the [[Cambridge Reference Sequence|CRS]] is a haplotype). Each marker is a DNA base-pair that has resulted from an [[single-nucleotide polymorphism|SNP]] [[mutation]]. Scientists sort mitochondrial DNA results into more or less related groups, with more or less recent common ancestors. This leads to the construction of a DNA [[family tree]] where the branches are in biological terms [[clade]]s, and the common ancestors such as Mitochondrial Eve sit at branching points in this tree. Major branches are said to define a [[haplogroup]] (e.g. CRS belongs to [[Haplogroup H (mtDNA)|haplogroup H]]), and large branches containing several haplogroups are called "macro-haplogroups".

[[File:Mitochondrial eve tree.gif|thumb|right|200px|Simplified human mitochondrial phylogeny]]

The mitochondrial clade which Mitochondrial Eve defines is the [[species]] ''[[species:Homo sapiens|Homo sapiens sapiens]]'' itself, or at least the current population or "[[chronospecies]]" as it exists today. In principle, earlier Eves can also be defined going beyond the species, for example one who is ancestral to both modern humanity and [[Neanderthal]]s, or, further back, an "Eve" ancestral to all members of [[genus]] ''[[species:Homo|Homo]]'' and chimpanzees in genus ''[[species:Pan|Pan]]''. According to current nomenclature, Mitochondrial Eve's haplogroup was within [[Macro-haplogroup L (mtDNA)|mitochondrial haplogroup L]] because this macro-haplogroup contains all surviving human mitochondrial lineages today, and she must predate the emergence of [[Haplogroup L0|L0]].

The variation of mitochondrial DNA between different people can be used to estimate the time back to a common ancestor, such as Mitochondrial Eve. This works because, along any particular line of descent, mitochondrial DNA accumulates mutations at the rate of approximately one every 3,500 years per nucleotide.<ref name="Soares09">{{cite journal |vauthors=Soares P, Ermini L, Thomson N, Mormina M, Rito T, Röhl A, Salas A, Oppenheimer S, Macaulay V, Richards MB |display-authors=6 |title=Correcting for purifying selection: an improved human mitochondrial molecular clock |journal=American Journal of Human Genetics |volume=84 |issue=6 |pages=740–759 |date=June 2009 |pmid=19500773 |pmc=2694979 |doi=10.1016/j.ajhg.2009.05.001 }}</ref><ref>{{cite journal |vauthors=Gibbons A |title=Calibrating the mitochondrial clock |journal=Science |volume=279 |issue=5347 |pages=28–29 |date=January 1998 |pmid=9441404 |doi=10.1126/science.279.5347.28 |s2cid=29855766 |bibcode=1998Sci...279...28G }}</ref>{{efn|group=note|There are sites in mtDNA (such as: 16129, 16223, 16311, 16362) that evolve more rapidly, have been noted to change within intragenerational timeframes.<ref>{{cite journal |vauthors=Excoffier L, Yang Z |title=Substitution rate variation among sites in mitochondrial hypervariable region I of humans and chimpanzees |journal=Molecular Biology and Evolution |volume=16 |issue=10 |pages=1357–1368 |date=October 1999 |pmid=10563016 |doi=10.1093/oxfordjournals.molbev.a026046 |doi-access=free  |ref=none}}</ref>}} A certain number of these new variants will survive into modern times and be identifiable as distinct lineages. At the same time some branches, including even very old ones, come to an end when the last family in a distinct branch has no daughters.

Mitochondrial Eve is the most recent common matrilineal ancestor for all modern humans. Whenever one of the two most ancient branch lines dies out (by producing only non-matrilinear descendants at that time), the MRCA will move to a more recent female ancestor, always the most recent mother to have more than one daughter with living maternal line descendants alive today. The number of mutations that can be found distinguishing modern people is determined by two criteria: first and most obviously, the time back to her, but second and less obviously by the varying rates at which new branches have come into existence and old branches have become extinct. By looking at the number of mutations which have been accumulated in different branches of this family tree, and looking at which geographical regions have the widest range of least related branches, the region where Eve lived can be proposed.