The concept of Eve

Daniel Dennett, philosopher and Darwinian, introduced me to one of the most devastating arguments that I had ever read, in one of his many great books. (I cannot remember if it was his original argument or not). It concerned natural selection, populations, and humanity. It was an a priori-type argument for the concept of an Eve: a single mother for all of the existing human race.

It is like an a priori argument because we don’t need to test the argument against reality, but do need to know a little something about human reproduction. We simply need to make one or two quick assumptions: everybody has a mother; and we all only have one mother. (Aside from Zaphod Beeblebrox from The Hitchhiker’s Guide to the Galaxy, that second one is probably a safe assumption to make.)

The argument is simple, but mind-blowing in its consequences. It goes like this: take the set of every single person now living on the planet. It’ll be about 6.5 billion people or so. Now, take the set of their mothers, living or dead. That second set is necessarily less than or equal to the first set. It’ll be, maybe, 2 or 3 billion, depending on the average number of living descendents they’ve left. If you continue taking the mother’s of each set as you progress, it inevitably, invariably, inexorably reduces to one. (Think through it for a while, it makes sense). It might take several thousand generations to whittle it down to one, but it is inevitable, logical.

This last set of one woman is the ‘mother’ of us all, speaking figuratively. The woman who is the common female ancestor of every single living person on the planet is called by scientists, perhaps unwisely, Mitochondrial Eve. It goes without saying that this Eve is no relation to the Eve of Genesis and was most certainly not married to Adam. In fact, scientists studying human genetics postulate an Eve for the human race as living around 140,000 years or so and a y-Chromosome Adam about 60,000 years ago. In the scientific jargon, she is known as the matrilineal most recent common ancestor (MRCA) for all living humans. Eve will do.

In any case, this argument from Dennett blew me away for its use of recursive logic, set theory and overwhelming simplicity. It quite literally blew my mind with its clarity and forcefulness. But most of all for the set of implications it left behind.

First, there is a kind of reverse argument possible here. As we naively think back through the generations, we generally, as is only human, tend to think it a wonderful or special thing to be descended from someone famous. But it isn’t that difficult to be descended from someone famous, as long as that person lived long enough ago in history (and had a penchant for bedding fertile young women). For example, it is well known that Ghengis Khan fathered many, many sons who each then fathered many hundreds more each. Inevitably, those princes, being powerful and wealthy, each fathered, on average, even more sons and daughters than the average. Hence, about 8% of central Asians living nowadays descend from Ghengis Khan. It is, quite frankly, nothing special to say that one is “descended from Ghenis Khan”.

Interestingly, this can be equally applied to the theory, for example, that Jesus was a direct descendent of King David. Perhaps he was. But applying the logic above, we inevitably yawn at the meaning of it, if any. It could only be a theological fancy anyway, since Jesus’s descent or otherwise from David was a Christian claim, only broached to make spurious links to Biblical prophecies. It is unnecessary theologically, but genetically it makes even less sense.

Another consequence of this theory is that the Eve of the next generation may be different. It may be that Eve had two or more daughters who have left descendents. And it might be that one of the two lines is about to die out, right now, perhaps even today. As long as that last descendent is a woman and is about to die without giving birth to a daughter, then that line faces extinction (on the female side). It is inevitable that as time progresses, over the next 150,000 years or so, that this theoretical Eve figure moves forward in time continually. Sometimes a single individual might be Eve for several thousand years. But then, all of a sudden, she’d lose the mantle to one of her daughters, or granddaughters. Hence, it seems logical to argue that the Eve point will pass through this generation, but perhaps not for another 150,000 years or so.

There could be, living among us now, an Eve of a future generation. She could be sitting next to you in your local diner. She could be playing ball in that park. Perhaps she’s even running for President (shudder the thought). But, she is there. So, be nice to her, whoever you are. She could be the only surviving mother of a future human generation somewhere down the line.

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1 Comment

  1. Jim Nichols said,

    January 9, 2008 at 12:27 pm

    You did a really good job of giving an overview of the idea! I also don’t know where it came from but was introduced via Dennett as well. I’ll have to look over Darwins Dangerous and see if there is a citation…


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