Hey!
Introduction
Here is a quote some of you may recognize:
"I just saw an article the other day about the mitochondrial Eve (ME) in Nature, I think its funny that after putting down evolution for so long, scientists are now seriously considering we all descented from one woman, just like the genesis said all along! Times are surely changing!"
The problem with this statement is that it is kind of true, but it leaves the JW with an impression that science is finally beginning to dig up evidence for genesis, but scientists are just to dense to interpret it correctly. That is blatantly false. Let me give an example:
Both genesis AND evolution predict humans existed 5000 years ago, and that is what we find. However no creationist would think this is evidence that support creation over evolution.
Yet the ME, despite the fancy name, is nothing more than that situation in a different setting, and that is why no serious creationist would use it as an argument. So refuting it to a family member consist of nothing more than explaining them what it mean.
Mitochondrial Eve for dummies
Consider a group of 3 random woman and the following question: How many mothers do these women have?. The answer may be 1 (they are all sisters), 2 (two of them are sisters) or 3 (none of them are sisters). The key observation is that 3 women can never have 4 or more mothers. Thats it! Applying this on a greater setting, we can say for sure that a million woman will never have more than a million mothers, infact it is quite likely they have fewer since (presumeably) some of them are sisters.
This quickly lead us to the mitochondrial Eve: First, consider all women alive today. Secondly, consider this groups mothers - notice the two groups need not be disjoint (in case a mom and daughter is alive at the same time). We can apply our key observation to the second group and say with confidence that this group cannot be LARGER than the first. We may repeat this again and consider the group of mothers of all the women in the second group - again this cannot be LARGER than the number of women in the second group.
If we repeat this operation again and again we get groups of women where each group cannot be larger than the last - and in general it will get smaller each time a woman has more than one daughter [thus a reduction by 1/4th or something like that over each generation is not entirely unreasonable a priori]. At some point we are left with just one woman, whom we call the mitochondrial Eve. Whats special with her is that she is the direct descendant (on the maternal side) to all woman alive today, thats why she is called Eve.
The properties of ME
This emediately allow us to clear away some misconceptions. First off
Nobody has ever been surpriced by the existence of a ME. It is a logical conclusion that she must exist, just like it is a logical conclusion humans existed on earth 5000 years ago. If our genomen didnt show signs of a ME, we would need to come up with some pretty funky rationalizations to make evolution work.
Secondly, the ME was not the only woman alive at the time - plenty of other women coexisted and some have living descendants. The mitochondrial eve only talks about a strictly maternal lineage.
Thirdly, you can do the same argument with men instead of women and get 'Adam'. This does not mean they knew each other.
Fourth, The reason scientists care about this is that one can use these observation together with statistics and genetics to get an idea about how man evolved. What we find is that the ME lived about 200'000 years ago, and 'Adam' lived about 50'000 years ago. Furthermore, it allow us to trace how humans have migrated when the world was populated. This is why no creationist bring up the issue on his own - he know it is very strong evidence against the creation myth, and the only real defense is 'well the water canopy magically fix everything that has to do with genetics, without leaving a trace!'.
Fifth, The dangerous word 'mitochondrial' refers to a certain part of the genomen found in humans which are only inherited from mom to daughter - this, and other properties, make the statistical analysis easier and is the reason why scientist work with Eve rather than Adam.