Mitochondrial Eve

Mitochondrial Eve is the woman who was the most recent common female ancestor of all humans alive today if they were to trace their ancestry backwards only through the female line.

Strictly speaking, Mitochondrial Eve does not have to have been a human at all. She could have been any of the ancestors of the human race, a primate, a fish, or even an earlier, simpler multi-celled organism. However, research has suggested that she lived in Africa somewhere around 140,000 years ago and since archaic Homo sapiens seem to have first evolved around 250,000 years ago, she would have been human.

The clue to why Mitochondrial Eve is theoretically traceable is in her name. All living cells contain organelles known as mitochondria which contain their own DNA and the mitochondria in the fertilized egg derive solely from the mother.

It's important to remember&mdash;unless you're a young Earth creationist, of course&mdash;that her mate was not the analogous "Adam" (most recent common male ancestor, Y-chromosomal Adam)&mdash;in fact, there are some studies going around that Eve is twice the age of Adam, and the Bible was very clear that Adam was not into older women.

List of common misconceptions, debunked

 * Eve is not necessarily, and probably isn't, the most recent common ancestor of all current humans. That common ancestor may have lived much more recently than Eve: perhaps as recently as 5000-2000 years ago. See for an explanation.
 * There would have been other women, probably many, many other women, alive at the same time as Eve. Many of these women will have descendants who are alive today. The difference between Eve and all her female contemporaries is that the latter all have at least one male in every line of descent from them.
 * Eve will have had ancestors of her own. She is not the first female human (although Homo sapiens sapiens did seem to emerge around the time of mtEve).
 * There will also be a most recent ancestor theoretically traceable through the male line. This man is sometimes called Y-chromosome Adam. It is unlikely that Y-Adam and mtEve knew each other, or even, depending on who you ask, lived in the same time
 * The mythology of one mother of the human race is contradicted by theories of speciation in which the line of humankind never "bottlenecked" into only two parents. In descent with variation, the predecessor species to homo sapiens changed gradually, such that (in retrospect) there were never fewer than 2,000 breeding individuals (and possibly at least 10,000 individuals) of our species. In other words, evolution never flipped a switch where a single ape mother suddenly give birth to a single human baby. Speciation can be somewhat grey as any organism X could mate with its parent Y and produce fertile offspring, so they would still be considered to be the same species. It's not a sudden jump, but a smooth transition. The issue, as Richard Dawkins pointed out, wasn't a problem with evolution, but a result of our habit of trying to draw specific dividing lines in what's really a spectrum. A similar issue comes up in classifying languages vs. dialects when we're faced with a
 * People always inherit their mitochondria from their mother. Sperm cells do carry mitochondria. While it is almost always the case that the sperm's mitochondria are destroyed during fertilization, there have been a few documented cases of people inheriting mitochondria from their father. These turned up during research into familial mitochondrial diseases.

Creationist misunderstandings
Hilariously, some creationists have taken this to mean that science has found the biblical Adam and Eve and evolution has thus been disproven. But they probably weren't contemporaries and almost certainly never met. They aren't even fixed people; if branches of Adam's male line or Eve's female line die off, the title shifts to whoever currently meets the definition.

Creationists wilfully misunderstand the entire notion of Mitochondrial Eve. Since the concept was first introduced in 1987 by A.C.Wilson et al., creationists have been deliberately claiming that she must have been the first woman. They believe this because it says so in the Bible, and such is the addled state of their brains that they need no further proof. It really is most unfortunate that did not call Eve by some other name. We might then have creationists wittering on about someone called Mitochondrial Doris instead.

Answers in Genesis thinks for some reason that Mitochondrial Eve was not the Biblical Eve but Shem's wife.