The mitochondrial clade which Mitochondrial Eve defines is the
species 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
Neanderthals, or, further back, an "Eve" ancestral to all members of
genus Homo and chimpanzees in genus
Pan. According to current nomenclature, Mitochondrial Eve's haplogroup was within
mitochondrial haplogroup L because this macro-haplogroup contains all surviving human mitochondrial lineages today, and she must predate the emergence of
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.
[30][31][32] 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, 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: firstly and most obviously, the time back to her, but secondly 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.