Mitochondrial Eve and you

By Sean Carroll | January 30, 2006 1:48 pm

We’re all brothers and sisters under the skin — or at least distant cousins. According to the popular Single-Origin Hypothesis (the “Out of Africa” theory), the human race originated in eastern Africa something like 100,000-200,000 years ago. The alternative Multiregional Hypothesis (which seems less likely to me, but what do I know) says that Homo sapiens evolved independently in several places, but even then there were Homo habilis ancestors that evolved in Africa — the question is really which populations should and should not count as Homo sapiens.

That means that we share common ancestors. And no, you needn’t be one of the three million Irish descended from Niall of the Nine Hostages, or the sixteen million people worldwide descended from Genghis Khan. If you go back far enough, you’ll eventually hit the human race’s most recent common ancestor, some lucky breeder with billions of living descendants — possibly as late as the first or second millenium BCE. We can also imagine tracing back to Mitochondrial Eve and Y-chromosomal Adam — our most recent common ancestors through purely matrilineal and patrilineal lines, respectively. (Adam and Eve didn’t know each other; he lived 60,000-90,000 years ago, while she was perhaps 150,000 years ago.) The point is, if you follow your family tree backwards, it keeps branching into more and more ancestors, and eventually all of our individual trees get mixed together. So, for example, Bill O’Reilly and Michael Moore are distantly related, although the family reunions are likely a bit awkward.

An obvious question is: how did we get from there to here? How did human DNA mix and match, spread out through various locales and ethnicities, and focus together to create that pinnacle of biological achievement: you? Well, a new project from National Geographic, IBM, Spencer Wells, and the Waitt Foundation aims to find out: the Genographic Project (hat tip to Maria). They are collecting DNA samples from all over the world, and using genetic markers characteristic of certain populations to infer how humans migrated across the globe, cheerfully (or not so cheerfully, often enough) reproducing along the way.

Best of all: you can participate! Sadly, you have to pay ($100) to join the project, rather than receiving recompense for your services; but it’s pretty cool. You get a kit that allows you to take a sample of your own DNA and send it in for analysis. The results won’t tell you about your immediate family, but they’ll reveal the geographical origins of your deeper ancestry. C’mon, you want to know where your haplogroup originated, don’t you? And we need to hurry, before the intimate (as it were) interconnectivity of the global village scrambles our genetic markers once and for all.

  • PLato

    Sean when pictures are used and we are sent to their site, this should open in a new window. In the site reference you might type target=_blanK after quoted url site link, so that if one closes the window you do not close your site right off.

    Anyway, the picture used in terms of probabilistic valuation reminds me of the statistcial analysis of binomial series, and the Marble drop, as well as pascal’s triangle. Picture then becomes self explanatory? Oui! Non!

    While it does not answer from where eve emerged, the very “action of eve”, might be another influence in science that we might all wonder about, in our moments of mystical wonder? :)

    “Polarities” in one form or another(?) just seem appropriate here, and “entropic actions” in all the manifested qualities and complexties of that first expression.

    Reminds me, of the professor crossing the room:)

  • Ken Muldrew

    Cavalli-Sforza, et al., have done similar work that you can read about in “The History and Geography of Human Genes”, but they had to labour mightily with the crude technology of the 80’s and early 90’s. It’s a pretty complicated story.

  • Steinn Sigurdsson

    Surely geographic isolation on at least two continents precludes common ancestry as recently as 2 millennia BCE? Must be at least 20 millennia BCE?

  • Amara

    References for the above:

    The History and Geography of Human Genes by Paolo Menozzi, Alberto Piazza (Contributor), Luigi Luca Cavalli-Sforza

    The Great Human Diasporas: The History of Diversity and Evolution by Luigi Luca Cavalli-Sforza, Francesco Cavalli-Sforza, Sarah Thorne, Heather Mimnaugh (Editor)

    Genes, Peoples, and Languages by Luigi Luca Cavalli-Sforza, Mark Seielstad (Translator)

  • Sean

    Steinn, I know what you mean, but apparently it’s just a few thousand years ago. Here’s the paper (pdf). The point, I think, is that colonizers from Europe and elsewhere went around, how shall we put it, sharing their genetic legacies with all the various populations they encountered, to the point where now even various aboriginal tribes will have at least one such ancestor. (Not that I know how much confidence we should have in the claim.)

    Plato, I think that most browsers give you the option of opening a link in a new window. I’d rather leave that choice up to the user, rather than force it on them.

  • Brian Lacki

    Dawkins brought up this in The Ancestor’s Tale, and mentioned that Tasmania has been isolated for 13000 years. So, Tasmania is probably the most isolated subgroup of humanity. However, it turns out that if anybody migrated to Tasmania in the intervening time and had children with the native population, there is a high probability (80%) that the entire Tasmanian population will be descended from them.

  • Count Iblis

    Brian, the Andaman islands were also isolated for a long time and this has been exploited in some genetic studies, see e.g. here.

  • CanuckRob

    My understading is that analysis of human genes reveals we went thorugh a “bottleneck” about 70,000 yers ago which reduced the human popualtion to less than 15,000 and we are all descended from that group. This would include the Tasmanians and all other subseqeusntly isolated groups.

    Sean mentions the theory that Homo Sapiens evolved several times and what that means for whom we cnsider to be human. Somewhat related is that there is a movment afoot to reclssify humans and the two chimps as all the same genus. Since the rules of zoological claissification require that the “oldest” name gets priority it means the chimps and bonobos are likely better described as genus Homo and not genus Pan. Welcome to the monkey house folks:) I for one am glad to welcome our new brothers and sisters and maybe we can stop killing them, infecting them and destroying their habitats. However based on how we treat other humans it seems unlikely.

  • John Hardy
  • Count Iblis

    CanuckRob, the Toba eruption is the suspect of having caused this bottleneck, see here.

  • Paul Valletta

    What baffles me, is that in the present time, any genetic mixing of close (family?), causes the breakdown of genetic corespondence, ie inter-bred family’s have genetic malfunctions. Now, if we can estimate that in a far distant past, there was a much less of a genetic pool, the population was sparse, and all societies must have been much more “inter-bred”, by fact of localized populations.

    Now it can be sumized that at the time of sparse co-habitions, there must have been a lot of genetic malfunctions, and for a great period of time in evolution terms?.. due to the population not really travelling great distances, to connect with another population, and thus another genetic (new) pool.

    This must have had a stumbling effect on all of societies?..due to isolations and the seclution of ancient tribes, there must have been a large number of deformaties?..and life expectancy must have been low due to the available genetic pool being “to-close”, in family terms that is. It was not until societies branched out and explored, and thus comunicated with new tribes, did the surviability of Man start to increase.

    What I am stating, is in the far distant past, the genetic pool was to tightly bound, to few peoples in isolation, and would have had a baring on the survivors to need travel and find “new” genetic partners?

    Without a great urge to move away and find new genetic code barers, Man would not be here today?

    Our ancestors had no knowledge of “inter-breeding”, dangers, which excludes the notion really that we could evolve from a single family of “brother+sisters”..”father+Daughters”?

    There must have been enough tribes, of certain isolations, to provide Man with just enough variation to evolve genetically?

  • Paul Valletta

    Oops..I just read the “most recent common ancestor” link..sorry!

  • donna

    All I know is I seem to have a damn site more bonobo in me than most people seem to. ;^)

  • Richard

    I recently heard that the chimps can be aggressive, nasty, and violent (even mortally violent) toward each other, whereas the bonobos live a summer-of-love peaceful kind of life. Which do we most resemble? :-) And some of our politicians?

  • Jim

    They really think that *everyone* in the world is descended from a European due to migration in the past 600 years or so? The Emporer of Japan? The King of Swaziland? Those isolated tribes in New Guinea? Call me skeptical. It seems any simulation would be way too sensitive to the assumptions it is built on, such as no inbred tribes.

    Even though I doubt this about today’s world, it probably won’t be many more centuries until someone (maybe, in fact, a European from the past few thousand years) dethrones the current MRCA, who I’d guess had had about a 50,000 year reign.

    By the way, does anyone know which *living* person is thought to have the most living descendants? Any guesses? There must be a pretty short short-list.

  • Arun

    No, Jim, the Emperor of Japan and the King of Norway share a common ancestor who lived some 5000 years ago. The isolated tribes just needed one or two entrants over the last 5000 years or so in ordr to share that common ancestor.

  • hal

    I may be a little cynical, but I have some questions about this project.

    1) Is $100 a fair price? Doing PCR certainly won’t cost that much per sample, although I’m sure there are other costs for analysis and running the project.

    2) Won’t there be a problem of over- or under-representation of some populations by collecting samples from people who can afford and are willing to pay $100?

    3) How useful is it to collect samples from non-native people of America or Australia, whose populations migrated very recently and have been mixing? Are they going to be categorized just as Americans/Austrarians of unspecified ancestry? Or are they going to be categorized as English, Irish, Italian, African etc. to understand migration of these sub-populations? What should people of mixed ancestries do?

    4) I guess getting information on ancestry of a population is different from getting information on ancestry of an individual. Suppose I have a genetic marker that is rare among my ethnic group. It’s difficult to know if this particular case means that one of my recent ancestors came from outside of the group or that my ancestors were rare carriers of the marker in the group. I can imagine that you can tell more about the population than an individual using statistics. But I suspect that many people who participate in this project are more interested in their particular ancestry (“my ancestors came from X and Y.”) than, say, how English and Scandinavians are related as populations.

    Is this really all about science, or is this also a business?

  • Alejandro Rivero

    It is interesting to thing hard on memetic here. A tale or a song fang by a grandmother to her ganddaughther does a time jump greater than a single gene, because it cross two generations. A “old wizard law” or a tabu, from the elders of the tribu to the youngsters, also does a big time jump, across two or three generations. But language differentiation, the big meme thing, seems to proceed at greater speed that racial differentiation (note that language does not bring, imo, a new “memetic species”; you can always learn the language of other men group, in the same way that you can have offspring from intercourse with any other group).

    Still, a century spans about five generational jumps, and the whole back to the 70000 years bottleneck (or whathever) is 2800 gene jumps, and perhaps only about 1000 meme jumps.

  • Poppycock

    I believe that the project is really more interested in indigenous populations than people who want to take part sending in $100. That is just a publicity stunt/money maker.

    Testing is being done on indigenous populations for free. However, there have been some difficulties, e.g. in New Zealand. The first I heard about the project was a report in the New Zealand Herald about the Maori being reluctant to take part. See for example here and
    (that one won’t come up as a link for some reason).

    They “know” their roots, and regard this as “scientific imperialism”. I think there may be similar problems with other populations. This article mentions a group called Indigenous People’s Council on Biocolonialism, who have similar concerns for native American populations. Hopefully enough people will volunteer to take part to ensure the study has sufficient data.

  • Count Iblis
  • Dumb Biologist

    100 bucks, eh? Oooo, and my monster tax refund is just burning a hole in my wallet even as I write this!

  • Jesse M.

    Here is an interesting blog entry from science writer Carl Zimmer on how more extensive genetic testing is providing more detail about human origins than just studying mitochondria as in previous studies–apparently these new studies suggest an interesting blend of “out of africa” and multiregionalism, with three major expansions out of africa at different times, and later waves interbreeding with eurasian populations that had come from earlier waves.


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About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] .


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