In a function / or a party occasionally, a familiar face walks to you and asks the question : "Do you remember who I am ? ".
You might reply "No".
(S)he might reply " I am your (fa/mo)ther's blah blah ..."
This is a very common situation, right ?
Now here is a very interesting study(at least I found this interesting) about relations which might startle that "familiar face" referred above :
Consider all the living females on this planet. They all have descended from a single female who lived about 1.25 million years ago. This female is called the mitochondrial eve. This is proved , because the mitochondrial gene passes on only from mother to daughter (not sons).
So mathematically :
Let x be an element belonging to F, the set of all females who are living today.
Then for all x, M(M(M(.........M(x)))))) = will lead to Mitochondrial Eve. M(x) is defined as Mother of x.
Now my questions to the reader who has kept his attention until this point:-
a) Was there a single Adam and Eve pair when this Mitochondrial Eve lived ?
b) Was she the only female living then ?
Update with Answer :-
Here is a graph which is showing the Mito eve of the 4th generation tracing back to the 1st generation.