cuz wiki has everything
http://en.wikipedia.org/wiki/Mitochondrial_Eve
"Common fallacies
[edit]Not the only woman
One of the misconceptions of mitochondrial Eve is that since all women alive today descended in a direct unbroken female line from her that she was the only woman alive at the time.[10][11] Nuclear DNA studies indicate that the size of the ancient human population never dropped below tens of thousands. There may be many other women around at Eve's time with descendants alive today, but sometime in the past, those lines of descent included at least one male, who do not pass on their mother's mitochondrial DNA, thereby breaking the line of descent. By contrast, Eve's lines of descent to each person alive today includes precisely one purely matrilineal line.[10]
[edit]Not a contemporary of "Adam"
Sometimes mitochondrial Eve is assumed to have lived at the same time as Y-chromosomal Adam, perhaps even meeting and mating with him. Like mitochondrial "Eve", Y-chromosomal "Adam" probably lived in Africa; however, this "Eve" lived much earlier than this "Adam" – perhaps some 50,000 to 80,000 years earlier.[12]
[edit]Not the most recent ancestor shared by all humans
Main article: Most recent common ancestor
Mitochondrial Eve is the most recent common matrilineal ancestor, not the most recent common ancestor (MRCA). Since the mtDNA is inherited maternally and recombination is either rare or absent, it is relatively easy to track the ancestry of the lineages back to a MRCA; however this MRCA is valid only when discussing mitochondrial DNA. An approximate sequence from newest to oldest can list various important points in the ancestry of modern human populations:
The Human MRCA. All humans alive today share a surprisingly recent common ancestor, perhaps even within the last 5,000 years, even for people born on different continents.[13]
The Identical ancestors point. Just a few thousand years before the most recent single ancestor shared by all living humans was the time at which all humans who were then alive either left no descendants alive today or were common ancestors to all humans alive today. In other words, "each present-day human has exactly the same set of genealogical ancestors" alive at the "Identical ancestors point" in time. This is far more recent than Mitochondrial Eve.[13]
"Y-Chromosomal Adam", the most recent male-line common ancestor of all living men, was much more recent than Mitochondrial Eve, but is also likely to have been long before the Identical ancestors point.
Mitochondrial Eve, the most recent female-line common ancestor of all living people."