Eve mitochondriale

The Eve mitochondriale is the name given by the researchers to the woman considered as most recent ancestor commune by maternal line of the Humanité. It is ancestor commune with all the current Humanité and bequeathed its DNA mitochondrial (ADNmt) to all the human ones.

The mitochondries are of Organite S cellular which are transmitted only by the ovule of the mother and it was shown that all ADNmt have a common origin. Eve mitochondriale is the female equivalent of Adam Chromosome there, the common ancestor most recent by paternal line.

By taking account of the speed of change (concept of the molecular Clock), in this ADNmt, calculations make suppose that the Eve mitochondriale lived some 150.000 years ago (148 000 front J. - C.). The Phylogénie suggests that she lived in Africa (today Ethiopia, Kenya or Tanzania).

Importance of Eve

Although the biblical name of Eve was given to him, the Eve mitochondriale was not the only individual female living of his time. Other women lived at the same time as it. These other women they also had descent, probably some of enter they are also ancestors communes with current Humanity, or ancestors common to a part only of Humanity. What characterizes the Eve mitochondriale , and all its ancestors by maternal line, is that it is the ancestor by maternal line only. Of her generation, only Eve mitochondriale produced an uninterrupted chain girls until today, and it was only from of which all the human alive ones go down in maternal line. The Mitochondrie S of the other women of its time disappeared, not having been transmitted to at least a girl. That does not want to say that they do not have a descent; the other women indeed had a made descent men and women, but not of pure maternal line. The descendants of these other women will have part of their genetic luggage, but the mitochondries of their maternal ascent, therefore those resulting from Eve mitochondriale.

The laws of fate coupled to a reduced population show that the least variation in the proportions of a Allèle within a population can quickly involve its domination or its disappearance by genetic Dérive, even if this allele does not have a differential effect in terms of Natural selection. It is the same for DNA mitochondrial.

It should be noted that the studies by computer simulation indicate that Eve is probably not most recent Ancêtre common of Humanity in the absolute, but most recent ancestor commune by maternal line. Other ancestors more recent communes contributed their share to various genes residing in linear DNA nuclear. For example, some ancestor more recent commune must have transmitted a gene which specifies a sub-unit of ARN in the Ribosome S. Cependant, since the reproduction mixes the nuclear DNA with the Chromosome S transmitted by the two parents, an ancestor commune more recent than Eve remains difficult to currently identify.

Chain events

The surprising fact that no other female line survived since the time of Eve rather seems a result of the chance than of the Natural selection. A female individual acquires the title d'" Ève" retroactively through an exceptional line of girls: in each generation of her descent at least a girl is giving rise to another girl. Eve takes possession of her “title” only when the lines of all the others claiming are stopped, the holder of the title could thus not have been identified by a test of alive sound.

Primarily, the hypothetical process by which all chalk-linings except one disappear is the same one as that of the genetic drift of the alleles. Just as for “fixing” or the disappearance of all the others Allele S during the genetic drift, the process of fixing Matrilinéaire is much slower and has much less chances to be carried out in a vast population than in small. If Eve had lived among million other women, it would be very improbable that the ancestors matrilinéaires of all the human alive ones today converge towards Eve (or another contemporary of Eve).

Why the community of Eve and her similar would have been so small? A possibility is that the world human population at its time passed by a bottleneck. Another is that Eve lived among a subpopulation of human arrival to supplant all the others. A version even more extreme of this scenario is than Eve had a very short life after some event isolating successor in title the Spéciation from the anatomically modern Humains . Among the remainders of the human skeletons oldest which were discovered, oldest to present bones comparable with human of today date indeed of the time to which Eve lived.

The relation with Adam

In addition, there exists a recent man, “the There-chromosomal Adam ”, having generated an uninterrupted line of males which are the aïeux ones of all the men of the ground. There-chromosomal Adam goes back only to half of the time passed since Eve. This wants to say that another bottleneck, in addition to that related to Eve, has affected human chalk-lining after it. The fact that the bottleneck at the time of Adam did not also produce an ancestor matrilinéaire common to all the human alive ones - more recent Eve, in other words - seems to indicate that the descent and the disappearance of a chalk-lining depends on the chance (unless the male lines are eliminated more quickly, because perhaps of the Polygamie, which would have made it possible only part of the males to have a descent). Nevertheless, certain researchers support that the obviousness of this second bottleneck also exists in the data of the DNA mitochondrial. It is as possible as the datings are erroneous, i.e. the shifted dates of Eve and Adam indicate imperfection of the theory of the molecular clock, which continues to undergo revisions.

Alternative theory

Another theory coming to compete with that of Eve is that the Spermatozoïde S could exceptionally contain paternal mitochondries whose DNA would recombine with the maternal DNA mitochondrial. It is about a daring assumption because it is generally allowed that the spermatozoa, of which the lifespan is short, draw their energy from a special device of microtubules, and not of mitochondries like the other cells of which the Ovule. explanation which seems incompatible with the preceding one: the spermatozoa comprise many mitochondries in the former part of whips but it is generally allowed that these last do not pass in the ovule. Nevertheless, if it proved to be exact, the mitochondries would not be a marker matrilinéaire as exclusive as it had been supposed. According to the frequency with which the recombination would occur, it could be that no Eve never existed. But no confirmation of this assumption was still obtained.

Eve and the African origin

One speaks sometimes about Eve mitochondriale like African Eve. The African assumption is established on the examination of the Fossile S as well as on the analysis of the DNA mitochondrial. The “family trees” (or “Phylogeny S”) built on the basis of comparison of the mitochondriaux DNA show that the human alive ones whose mitochondriaux chalk-linings constitute the first branches of the tree are the indigenous populations of Africa, while chalk-linings of native-born people of the other continents are born all from African lines. The researchers thus thought that all the human alive ones go down from Africans, of which some migrated out of Africa to populate the rest of the world. Also, many researchers take the fact mitochondrial like proof in favor of “the single origin ” or “ African Genèse ”.

The construction of family trees starting from the data of DNA is however an inaccurate science. The critics of the “African Genesis” claim that the fact mitochondrial can be explained as well, or even better, by trees placing Eve closer to the people of Asia. However, since 2003, following successive progress data processing methods of determination of the phylogenetic trees, the number of these criticisms fell. In any event, the greatest support which the DNA mitochondrial can offer to the assumption of the African origin does not depend on the trees. It is indeed among the African populations that one finds the greatest diversity of DNA mitochondrial, certain variations seeming to exist only in Africa. This diversity could not have accumulated, say the researchers, if the human ones had not lived longer in Africa than anywhere elsewhere. The analysis of the sequences of the Y chromosome also gave results in favor of a African origin of the Hominien S.

External bond

Animation illustrating the migrations deduced from the ADNmt.

References

Edge, R.L., Stoneking, Mr., and Wilson, A.C., 1987, " Mitochondrial DNA and human evolution" , Natural 325; p 31– 36
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Nicole Maca-Meyer, Anna Mr. González, Jose Mr. Larruga, Carlos Flores and Vicente Mr. Cabrera (2001) " Major genomic mitochondrial lineages delineate early human expansions". BMC Genetics Biomed central
Oppenheimer, Stephen. The Real Eve , Carroll & Graf, (2004) ISBN 0-7867-1334-8
Bryan Sykes The Seven Daughters off Eve: The Science That Reveals Our Genetic Ancestry , W.W. Norton, 2001,306 pages, ISBN 0-393-02018-5 (French translation: seven daughters of Eve )
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Spencer Wells The Journey off Man: In Genetic Odyssey , Princeton University Close, January 2003, hardcover, 246 pages, ISBN 0-691-11532-X
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