Talk:Mitochondrial Eve

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It should be stressed that “Eve” is an abstraction: as the most recent matrilineal common ancestor of living humans, it is possible for her identity to change, though it would now be necessary to kill off a large proportion of the human race in order to achieve this.

It's not really that dramatic; a large proportion of the human race is dying all the time in the normal course of events. The identity of "Eve" should be shifting approximately with every generation.

______________________

NO IT SHOULDN'T.

I'm not even going to argue with you, 'cos I'm tired, I'm just going to tell you to go away and think about it. It's a simple, back-of-an-envelope problem. Figure it out.

--- Dr A.

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A truly adequate response! I shall indeed think more upon the matter.

Suppose we have the following idealized situation:

A(m)  B(f)  C(m)  D(f)   <--“Eve”
 |     |     |     |     
 +--+--+     +--+--+     
    |           |           
 +--+--+     +--+--+     
 |     |     |     |     
E(m)  F(m)  G(f)  H(f)   
 |     |     |     |     
 |     |     |     |     
 |     |     |     |      
 +-----------------------+ 
       |     |     |     | 
       +--+--+     +--+--+ 
          |           |    
       +--+--+     +--+--+  
       |     |     |     |     
      I(m)  J(m)  K(f)  L(f) 

In this case D is "Eve", assuming that everyone EFGH and above died of old age. Now add another generation:

     I(m)  J(m)  K(f)  L(f) 
      |     |     |     |      
      +-----------------------+ 
            |     |     |     | 
            +--+--+     +--+--+ 
               |           |    
            +--+--+     +--+--+  
            |     |     |     |     
            (m)   (m)   (f)   (f)

And assume that everyone from IJKL up died of plain ol' death. No branches of the family have been pruned, and no "large proportions" have died. Yet "Eve" can now be identified as H, rather than D.

____________________________

Now let's think about a large, non-idealised situation, such as the real world. And we find that the most economical way to change the identity of Mitochondrial Eve is to kill off everone who's sub-Saharan African by maternal clade, and that the second most economical method is to kill off everyone who isn't.

--- Dr A.

___________________________

It is possible that I may have drawn an invalid conclusion from the "idealized" situation, although I am still not convinced that this conclusion is necessarily false.

But this makes me wonder if the (necessarily simplified) situation might cause more harm by leading to false or unsupported conclusions. I included it mainly to explain how multiple common ancestors could exist, not as a real model from which additional inferences could be drawn.

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The thing that most closely controls the exact placement of ME and XCA to some particular generation is the existence today of small pockets of relatively pure "primitive peoples", mainly in Africa. As these populations die off without issue, the ME and YCA could move further down the tree of descendants (later in time). However, if some member of said small packet should manage to leave the geographical area (physically or culturally) and begin having descendants among the larger population, that pretty much puts a brake on the location in time of the latest common ancestors, as it becomes much more difficult to kill off all the descendants of a particular ancestor. As "racially" (inter-racially as well as intra-racially, as long as its outside the immediate tribe) homogeneous as we are today, these ancestors are pretty well fixed in perpetuity now, even for MEs and YCAs of smaller racial groups (mutation lines) than Homo sapiens as a whole. Shadron 10:55, 18 December 2008 (CST)