Understanding Mitochondrial Eve

(Advance note: Is there a reader who has video editing skills who might want to put together a short and amusing BSG-based parody video that I have conceived of? Contact me if so. Or if you have a complete collection of BSG videos or DVDs and are willing to find some scenes you could also help.)

Because it turns out that Moore decided to turn the entire plot around the idea of Hera being Mitochondrial Eve (MTE), I thought it would be good to add some information on just what this means, and why it was not a great choice as a plot fulcrum. The desire to have Hera be MTE placed the story 150,000 years in the past, and mandated a number of its less consistent elements.

First of all, people should understand that MTE is not "Eve" (mother of us all) nor is she the most recent common ancestor of us all -- that person lived far more recently. MTE is an artifact of some simple genetic math. She is the most recent common ancestor calculated only through female lines. I pointed to this article about MTE before and it's worth a read to understand why she exists and why she is less important than imagined. There is a "Y Adam" too, who is the most recent common ancestor calculated only through male lines, who also lived much more recently.

Everybody is descended from MTE, but everybody is descended from almost everybody who lived at that time. She is actually not particularly special. In fact, we are all descended from almost everybody who lived about 15,000 years ago. It would be more recent than that if human genetic lines had not been isolated for long periods in Australia, the Americas and a few other islands. Be clear: Just about everybody who lived then was ancestor to all of us. The only ones we are not descended from will be those whose lines died out quickly -- they left no children or grandchildren. Once you start have several great-grandchildren, your contribution to the world's genetic pool is all but assured, barring extraordinary events. Go a few more generations and your line is very hard to kill off, especially if it spreads a bit.

So while Moore wanted humans to be descended from Cylons, in fact that could have taken place 15,000 years ago. And if, as shown in the show, populations were distributed to the different continents, it could have been done even 4,000 years ago, or any point in between such as 40,000 years ago for the "great leap forward" when technology and agriculture and language started to really flourish. Australians isolated themselves from the rest of humanity about 50,000 years ago, however, when seas were low they got more recent influxes keeping them related to the rest of the world.

The next thing to understand is mitochondrial DNA (MTDNA) itself. MTDNA is special, in that it is only inherited from your mother. It does not change due to sexual DNA mixing like the rest of our (non-Y) DNA. Instead, it stays mostly the same. However, from time to time, it gets a small mutation that is not sufficient to kill the organism. So while our MTDNA is identical with our siblings, mother and our cousins who share a female descent line, it is very slightly different from other humans. The less related they are to you (ie. the further back your common great^n grandmother is,) the more slight differences there will be. It is precisely because we know the rate of mutation and can look at how different the MTDNA of different humans is that we can calculate when MTE lived, approximately. Estimates get debated, and you will see rates quoted at one mutation per 300-600 generations down to one every 40 generations.

But we don't just share our MTDNA with our fellow humans. We share it with all the complex life on Earth. We share it with mushrooms and of course with chimps and monkeys and lemurs and mice. We've all got the same basic MTDNA, derived from an ancestor long ago that did a symbiotic "deal" with some bacteria to incorporate their energy processing engine into our cells.

Just as you have the same MTDNA, with minor changes, as an Australian aboriginal, you have the same MTDNA as a chimp, but with more of the small mutations. That's because your common ancestor lived perhaps 50,000 years ago with the Australian, and 6 million years ago with the chimp. There will be 120x as many small differences. They are quite small so that does not turn out to be that much.

And thus we see the problem with how BSG used this process. On the BSG Earth, the chimps and the early humans would have shared fairly common MTDNA. But then Hera's MTDNA replaced the human MTDNA. On BSG Earth, human MTDNA now bears no common ancestry with the chimps, or all the other animals of the Earth. This is quite different from the real Earth.

Now, we might consider that in fact they are not different because the God of Galactica (Gog) did a little intelligent design on both the evolved Earth life, and Cylons so that they would have the same MTDNA. Or rather that the difference between them would match what the genetic mutation clock says it should match based on the time back to the common ancestor proto-ape. And yes, when you invoke miracles, you can pull off anything, I suppose. But if so, it means the two sets of MTDNA were largely identical. In which case what's the point? What is the meaning of Hera's MTDNA supplanting that of the native humans if the two are identical to begin with?

If they are not identical, if there is a real, meaningful difference between Hera's MTDNA and that of the rest of Earth-life, then this would have been big, big news in BSG-Earth's National Geographic a decade or two ago. That's because geneticists would have published stunning papers revealing that human MTDNA was not the same as that of apes or any other Earth life. This would have turned the scientific world upside-down. It would have have been strongly touted as hard evidence by the creationists. It would no longer be the world we live in.

This is also true for the rest of Hera's Cylon DNA. Unless that DNA is impossible to tell from ours, or unless none of what she had was passed through to us, our genetic sequencing projects would have revealed the fact that we aren't related to other Earth life, in some subtle way. We would have proteins and genes not found in any other Earth-life. But we don't. We share all our genes with our animal cousins. For those, like Moore, hoping to draw a connection from the alternate history BSG Earth and ours, you must either say that none of the Cylon DNA made it through, or that it was so identical as to not make a difference.

Of course, there is an answer, discussed on this blog before. If the story had been written to say that the Kobolians came about through the abduction of primitive humans from this Earth some 6,000 or more years before the events of the show, then of course everybody is still related as they should be. The colonials, in this version, are just a lost branch of Earth-kind come home. But alas, this was never suggested in the show.

The miracle of aliens who can breed with Earth-life is indeed impossible without divine action. But it's more than that. If there was a miracle, it created creatures so alike that in the end they contributed nothing new to the genetic code of humanity on Earth. In other words, a somewhat pointless miracle.

Now you may think that this is a somewhat subtle point, not known to the ordinary viewer who has no grounding in genetics. But this is no minor issue in the show, it is the single element upon which the entire ending, and indeed the entire plot was chosen to turn. Such a fulcrum deserves special attention. And it is also a sign of just how hard it is to try to write an alternate history which you can claim could be our real history. Something is going to catch you up. This is why many viewers never expected Moore to do something so foolhardy as to date the show in the past.


it's amazing how much stock you put into the prevailing paradigm of the MOMENT.

And it's amazing how willing people are to ignore mountains of evidence. Doubly amazing to see how many people interested in science fiction are willing to do so. We know an awful lot about mitochondrial DNA. We can compare the mDNA of any two organisms to see how closely related they are. We can also tell about what time frame the most recent common ancestor lived.

Way too much time to waste proving a fictitious show is wrong. This is more about your inability to accept that you were wrong, than it is about proving RDM is wrong... RDM was never out to provide a factual account of the history of mankind or it's development.



Mitochondrial Eve is the most recent common matrilineal ancestor to all humans living on Earth today... This is the common knowledge. For you to go digging up as much hard science, that most people do not know, in an effort to simply discredit a fictitious tv series, which ended in a way you didn't like, shows a serious brain dysfunction... And maybe it's contagious, because I'm here actually engaging in this asinine shit.

The concept of Mitochonrial Eve is not that widely understood. This is illustrated by numerous posts from people who don't understand the concept, for example, believing that it meant that no one else but Hera had children.

No one ever claimed that RDM was attempting to create a factual account of world history. We understand fully well that it is fiction.

It is correct that if Colonial mDNA and native Human mDNA were identical, that no one would would be able to tell the difference. But the probability of that is so mind-bogglingly low that it is awfully hard to swallow.

If you think that thinking is a waste of time, feel free not to waste your time.

Actually, RDM has sort of said that. He writes that they kicked around having Galactica land, broken, on Earth and being buried over time. Then they would have had the National Geographic be a story about some new archeology in a series of strange mounds (which he says are real, I don't recall where they are) and the high-tech material found inside them.

He says he rejected this story because it is not real. That this would quickly say to the audience, "This is an alternate universe" because in the real universe we have not encountered spaceships buried in the ground. He went to the MTE story precisely because he mistakenly thought it made a stronger connection to our real world.

What he didn't understand, and what his science advisor failed to tell him, was that there would be a "crashed alien ship" hidden in our DNA and we would have found it -- and thus this is just as much an alternate history as the one with the real crashed ship.

I realize that Cylons and colonials had DNA Cottle could not tell apart, the Cylons having been made by genetic engineering from Kobolians. However, the Cylons had protocols to tell them apart, and Baltar also eventually made a system that could tell them apart. But there had to be a difference, and frankly that the difference would be so small is a bit hard to credit, since Cylons have super-strength, can stick fiber optic cables in their arms, communicate digitally by touching water, share memories, and transmit FTL updates of their brains instantly if they die.

However, I was referring not to this difference, but the difference between native Earth creatures and the Colonial/Cylon family. Two sets of independently evolved creatures, made able to mate through divine intervention. There, if you want to accept the BSG story, there was no difference, which makes one wonder what the point of the story was. The colonials and Cylons land on Earth, and mostly die out, and leave DNA in our bloodline that is indistinguishable from the DNA that was already there?

It doesn't matter if the show is fictitious or not for Brad to be right. RDM decided to make MTE a part of the history of our earth but was inconsistent with the delivery. I could give a shit less about the plot as long as it makes sense and is entertaining. It stopped being entertaining a while before the the finale and it sure as hell was inconsistent. If RDM didn't want us to question his plot lines in this manner he should have been a little less serious in presenting them that way from the start.

I just wanted to stop lurking long enough to leave a general compliment. Brad, your site is fun and thoughtful, and I appreciate the efforts you have made with it. Admittedly I do tend to agree with the Brad viewpoint more often than not, but I do have to wonder why so many commenters resort to ad hominem attacks.

And on a more specific note, that was a pretty good explanation of mtEve, especially without the use of diagrams (some gene genealogies would make gene coalescent theory a lot easier to understand for the average internet Joe). I can think of a few clarifications that I might suggest, but I am too tired to be coherent at the moment. Maybe I will try and lay them out later.

P.S. Keep up the good work! I'm sure fan appreciation of Caprica will benefit this level of analysis and constructive criticism.

Wow, I beat Ron to the punch for an ending *again* (with Stanley Kubrik's help)

So, we've got hunter-gatherers wandering Earth some blah years ago and race with super advanced technology. Ron makes the high-tech people send all their ships into the sun and has the high-tech people breed implausibly with the natives. Instead of being cool...

[Adama] "Take the fleet beyond the asteroid belt, and set it to orbit at minimal power in a Lagrange point behind that large gas giant.

[Anyone] If we set it on low power, how will it know when to wake up?

[Adama] Bury a transmitter on the moon's dark side, have it send out a wake-up signal as soon as it gets exposed to light.

[Anyone] How will anyone know to dig it up?

[Adama] Draw maps in the caves of some of the primitives...

After so much Blade Runner, a 2001 ending would have been pretty cool. Instead of being Humanity's Children literally, the people of Earth could have been Humanity's Children figuratively.

Of course, Earth gets the Colonial Fleet just in time to defend against Cavil's cylons, well, this has all happened before, it can all happen again...

I must have missed it somewhere, but what was so special about Hera?

After 4 seasons of telling us that Hera is IMPORTANT, BSG dropped the ball at the end by not telling us why she was so important.

You guys do realize that this is fiction, right?

We thought it was a documentary. Thanks for informing us so politely.

Yes, we know it is fiction. No one is saying or implying that it isn't fiction. Your point seems to be that no one should critically examine fiction. However, literary criticism isn't exactly something that has been dreamed up overnight. Just because something is fiction doesn't mean it cannot be examined. Literary criticism has been going on since the first story was writtin on a clay tablet.

Perhaps the problem is that the BSG audience draws not just from the traditional science fiction fandom, who are used to concepts such as literary criticism, but also from soap opera fans, who are not.

Cylons were distinct from human/Colonials, but that difference was impervious to detection by DNA analysis. Cylons appeared human/Colonial, subject to typical genetic differentiation. There were additional, shall we say "components", some kind of nanotechnology, that went beyond DNA. Whatever they were, it permitted Sharon/Athena to stick electronic circuits into their tissues and tap into those technologies.

Whatever made Cylons distinct passed into Hera and would, presumably, into her ancestors.

The identification of Hera as Mitrochondrial Eve means that contemporary humans are Cylon, or partly so, as we have that nanotechnology in our make-up.

We don't have it. Again, that is fine for an alternate reality, but Moore claims he did the ending the way he did to make it more connected with our reality, not less.

Well we wouldn't have any cylon in us any more. There were a limited number of cylons in the fleet who landed on Earth, and it's entirely possible that Hera was the only one to procreate, or at least one of a limited few. Over the millennia that followed, her cylon heritage would have been thinned to the point where any 'nano-technology' or whatever set them apart from the colonials would have probably been rendered moot. It's also possible that her line ended at some point and only human/human pairings survived.

Plenty of reasons to dislike the finale-- this, again, is not one of them. Move on.

Again, I speak of Moore's goal, which was to say we all had Cylon in us. Indeed, for any random human, their genetic contribution after 7,000 generations becomes insignificant. (It is true that your mitochondrial mothers have a near 100% contribution of mtDNA to their female line, and 0% contribution to those who descend via males.)

Since Cylon DNA is superior, however -- we believe it confers superior strength, intelligence and a cancer immunity, while also offering a digital brain with the ability to project -- it should normally contribute far more than average. We don't know for sure if Hera or other hybrids obtain all those traits. We only see her have the cancer-curing blood and the ability to project, but it would be odd if she doesn't get some of her mom's other abilities, and the same should be true for other hybrids that appear.

It's obvious why genes for such strength and intelligence might survive, unless they come at a high cost (needing more food, etc.) and in fact, the enhanced communication ability of projection sounds quite useful too.

(As to why strength might not survive -- it has a cost. Looking at how much stronger other apes are, it seems likely we used to be much stronger, and lost it because we did not need it. Cylon strength, however, is not naturally evolved, it is synthetic, so we can only make limited predictions about what it would do.)

There's good stuff, as you say in NuGalactica but after a while the use of the movie synthesizer gets a bit tired. It's cute to see characters saying it, but there is also real meaning in the messages and they are more quickly.

What disturbs me is that I keep seeing more essays on how much the ending sucked, often exploring new ideas not found in the others, and they are largely right. My own final review, if I take the time to write it, is going to be called "The worst ending in the history of SF on the screen" which sounds like something very nasty, but it's actually high praise, in its way. High praise because I mean the most disappointing ending -- the greatest fall. To have the greatest fall, it was necessary to start very high -- that's the high praise part.

Some points I haven't seen mentioned (but they might have been)...

- Only a minuscule proportion of prehistoric humans have had their remains dug up. The chances of Mitochondrial Eve's remains being found are absurdly small.

- I suspect (but could be wrong) that even if her remains were dug up and her DNA could be recovered intact, it would not be possible to identify her as Mitochondrial Eve, but only as someone who was more or less closely related to Mitochondrial Eve.

- Regardless of how much Cylon DNA we have inherited, it's clear that none of that Cylon DNA has had any detectable effect on us. We appear to be functionally identical to the Colonials. Why should "God" care whether we have some Cylon DNA if it doesn't have any effect on us and we can't detect it? (Devil's advocate response: we could detect it in the future, and knowing we are partly descended from "machines" might discourage us from repeating the old cycle.)

That reminds me of something else. It always bugged me that the skinjob Cylons were referred to as "machines", even by themselves and by sympathetic humans. (It's understandable that unsympathetic humans would denigrate them as "machines", "toasters", etc.) They are quite clearly living organisms, even if artificially created.

Correct. A huge number of people would have the same mtDNA as mtEve -- perhaps 300 generations of people, in theory it could be many millions. So no, they could never identify one person in a fossil bed as her. The reason we know it's her is the angels say it's her.

But actually, since so many millions would have the same dna as her, the odds of digging up somebody who could not be told from her is higher.

Yes, they are living, biological organisms. The colonial prejudice is one of the more interesting parts of the show.

Was just one of many strange things. But you must realize that science aware fans expect the science in TV and movie SF to suck. So that's why they were open to past or future. If they sat and thought about it for a bit, they would have said, "well, in reality, this could only be in the future" because they would not have bought into collective unconscious, among other things. They could not sing Dylan songs and quote Shakespeare in the past, without the racial memory thing which upon more serious inspection, is silly. And certainly anybody with knowledge of genetics and evolution would have concluded that, even if the show were to be set in the past, it would not be the case that aliens would be our ancestors or partial ancestors.

Now most would not have expected this problem of interbreeding to be solved with divine will. With divine will you can make anything work, of course. But were the people you read comments from saying, "It would be very silly, but it would be consistent if they explain it as a miracle?"

But we suspend our disbelief. This is one reason that the Rod Serling ending from Planet of the Apes is so good. If you look at the movie for more than a few moments with a rational mind, you notice that they are speaking English. And they are apes and humans. Normally this would make the viewer immediately conclude "this must be in the future, and on Earth or a colony of it." Yet the vast majority of the audience was surprised. I was surprised, but I was 8 years old. They are surprised because we normally just accept aliens speaking English in our SF TV and movies, because it's necessary for dramatic reasons.

So I think that the fans who were ready to have it be in the past were mostly doing that. Just suspending disbelief on the things that would be silly in the past. And ignoring (correctly it turns out) the botched clues of the Tomb of Athena.

I agree that nothing is perfect. But there are levels of quality. Accepting that the apes of the future on the Planet of the Apes spoke 20th century English is vastly less of a leap than accepting that apes and humans would live and speak 20th century English on a random planet. So vastly less as to be ridiculous. But again, this is what was good about the ending. It shocked the audience by being the obviously right answer. A truly great twist ending has you saying, "Of course, now it is so obvious."

But there are levels of quality, and this is one place I disagree. I think that BSG was one of the higher quality shows in this regard by a good measure. It's part of why I and many others got invested in it. That it was one of the best, and then squandered it, when it could have so easily gone out with high quality and realism, is what upset the viewers like me.

We let our shows take liberties with reality all the time. Then we judge "was that worth it?" Nobody thinks Lord of the Rings is real, but we happily accept the wizards because the goal is to read a great story of high fantasy.

Moore's choice of MT Eve fails the test of being worth it because it would have been so simple to do it better. So the story got turned around, the whole colonial culture ended up erased, not simply for nothing, but for something scientifically wrong. That's not worth it.

I wonder what the series would have looked like if RDM had instead decided to base his "ancient link" in BSG on Ida, the 47 million-year-old primate fossil that is in the news now, instead of Mitochondrial Eve....
I can see it now... " Who founded The lost ancient civilization of Lemuria millions of years ago?"

It was the "Space Lemurs"!

I'm betting we'll see somthing like that soon on the Cartoon Network. That, or Pixar / Dreamworks project...

It's rather late, so rather than make a complete thesis, I'll leave it to this smart group to explore.

While it seems more likely that the show writers didn't give nearly as much though as the many people here have, there is still a significance to Hera. Not is sharing common DNA, but in preserving another _significant_ show concept: Collective and inherited memories or consciousness. This lends well to a lot of key points, right up to and including head six and head Gaius persisting in present day.

There were so many memory flashes in this series. MTE sure, exact same DNA sure, it was the union that mattered to either prevent, or chase, it all to happen again. (Take your pick on that one.)


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