According to the most common interpretation of the mitochondrial DNA data, the titles belong to the same hypothetical woman. Mitochondrial Eve is sometimes referred to as African Eve, an ancestor who has been hypothesized on the grounds of fossil as well as DNA evidence. But scientists still disagree on whether these processes do occur, and if it turns out that they do, they may not occur frequently enough to make Eve or her identification impossible. Depending on how frequently paternal inheritance and recombination occurred, as well as when they occurred, it may be that no Eve even existed. So mitochondria may not be so pure a matrilineal marker as they were supposed when the theory was advanced. Still other evidence suggests that sperm and egg mitochondrial DNA may 'recombine', or swap pieces of sequence with each other. It is also possible that the mismatched dates of Eve and Adam may illustrate the weakness of the molecular clock technique, which continues to undergo revisions.Ī recent challenge to the Eve theory has been the observation that the mitochondria of sperm are sometimes passed to offspring. Some researchers says evidence of this second bottleneck exists also in the mitochondrial DNA data. The fact that the bottleneck in Adam's day appears not to have produced also a matrilineal ancestor of all living humans-a more recent Eve, in other words-illustrates that the branching and disappearance of lineages depends on chance. This means that another bottleneck event besides the one surrounding Eve affected the human lineage after her. On the other hand, the most recent common ancestor to father an unbroken line of males, ' Y-chromosome Adam,' appears to have lived only about half as long ago as Eve. Of the ancient human and hominid remains discovered so far, in fact, the oldest that match the bones of living humans date from around the time that Eve lived. A still more extreme version of this latter scenario is that Eve lived shortly after whatever isolating event caused the speciation of anatomically modern humans. Another is that Eve lived in a subpopulation of humans that came to supplant all others. One possibility is that the world population of humans in Eve's day passed through a bottleneck.

The observation that the mitochondria of living humans point to a common ancestor represents evidence that this ancestor lived in a much smaller breeding pool than humans live in today. If Eve had lived among a million or a billion other females, it is very unlikely that all humans alive today could trace their descent to Eve (or to one female contemporary of Eve's). As with genetic drift, the process is much slower and much less likely to reach completion in a large population than in a small one. Essentially, the hypothesized process by which all lineages but one disappear is the same as genetic drift. This is assumed to be an effect of chance rather than selection. But of the females of her day, only Eve produced an unbroken line of daughters that persists today.

Researchers believe as many as 20 000 individuals of Eve's species may have lived at the same time as her. Family trees suggest she lived in Africa.Īlthough researchers named her after the Biblical Eve, mitochondrial Eve was not the sole living female of her day. Based on the molecular clock technique, Eve is believed to have lived about 200 000 years ago. Under the assumption that an individual inherits mitochondria only from his or her mother, this finding implies that all living humans descend from one woman-possibly one pre-human woman-who researchers have dubbed Mitochondrial Eve. A comparison of the mitochondrial DNA of humans from many races and regions suggests that all of these DNA sequences have evolved molecularly from a common ancestor sequence.

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