It does not mean that she was the only woman of her time who was ancestral to modern humans.

In other words, mitochondrial Eve was not a Biblical Eve. However the Biblical Eve, if she

had existed, might well be mitochondrial Eve Mitochondrial Eve The concept of "mitochondrial

Eve" is widely misunderstood. It does not mean that she was the only woman of her time who

was ancestral to modern humans. In other words, mitochondrial Eve was not a Biblical Eve.

However the Biblical Eve, if she had existed, might well be mitochondrial Eve (though not

necessarily: it could be one of her female Eventually the set will contain only one woman,

who is known as "mitochondrial Eve". The mtDNA of all living humans is inherited from

mitochondrial Eve. Normally our mtDNA is identical to that of our mother. But, like all DNA,

mtDNA mutates occasionally so that one of the bases
     changes to a different base. Because of these mutations, human mtDNA has been slowly

diverging from the mtDNA of mitochondrial Eve, and the amount of mutation is roughly

proportional to the amount of time that has passed. This means that similarity of mtDNA for

any two humans provides a rough estimate of how closely they are related through their

maternal ancestors. If they have identical mtDNA, they are fairly closely related, maybe

even siblings. If they have very different mtDNA, it means their last common maternal

ancestor lived long ago. However, using the genetic difference to estimate the time of the

last common ancestor is difficult, for a couple of reasons. One is that the rate at which

mtDNA mutates is poorly measured. The other is that even if the average mutation rate is

accurately known, some lineages will as a matter of chance accumulate fewer or more

mutations than average.