"Adam," "Eve," and why they never got married.

In a recent Panda's Thumb comment thread, [Pam asked](http://www.pandasthumb.org/archives/2007/07/lets_talk_junk_1.html#comment-188417) (among other things) about our human species genetic Adam and Eve:

I have been reading for the last few years now, that there is a consensus among the majority, that humans have been genetically traced to a two human ancestory: A genetic "Adam and Eve".

This is a relatively common misconception, and a very understandable one. There have been published studies that have looked at the most recent common mitochondrial DNA ancestor of all humans, and other studies that have looked at the most recent common Y-chromosome ancestor of all humans. Since mitochondrial DNA is only inherited from the mother, the most recent mitochondrial DNA ancestor is frequently referred to as "[mitochondrial Eve](http://en.wikipedia.org/wiki/Mitochondrial_eve)." Similarly, since the Y-chromosome is passed on exclusively from father to son, the most recent Y-chromosome ancestor gets called "[Y-chromosome Adam](http://en.wikipedia.org/wiki/Y-chromosomal_Adam)" a lot. The use of those two terms is not entirely inappropriate, but it can be very misleading - particularly for those who haven't taken a bunch of college-level biology.

Let's start with the biggest misconception, and move on from there. When it comes to Adam and Eve, there's good news and bad news. The good news is that I can unequivocally state that they never got divorced. The bad news is that they never married. That's understandable, of course, since Eve died more than 50,000 years before Adam was born.

Right about now, I'm guessing that we're hitting the point when confusion sets in. After all, if every man on earth is descended from Y-chromosome Adam, and if we're all descended from our fathers, and if Y-chromosome Adam was married, why wasn't his wife "Eve?" We all clearly must be descended from her, too, right? (And if confusion hadn't set in already, it almost certainly has now that I wrote that.) Let's see what (if anything) I can do to clear things up.

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