The X-Woman's Fingerbone

By Carl Zimmer | March 24, 2010 2:05 am

In a cave in Siberia, scientists have found a 40,000-year old pinky bone that could belong to an entirely new species of hominid. Or it may be yet another example of how hard it is to figure where one species stops and another begins–even when one of those species is our own. Big news, perhaps, or ambiguous news.

In Nature today, Svante Paabo and his colleagues published a paper describing their work in a place known as the Denisova Cave in the Altai Mountains of Siberia. There are lots of hominid bones and tools indicating people lived in the cave, off and on, for 125,000 years. There’s good evidence of Homo sapiens in the region for at least 40,000 years, and Paabo and his colleagues have also isolated 30,000-year old DNA from Siberian sites that is similar to the DNA from Neanderthals in Europe.

The scientists succeeded in fishing out human-like DNA from a pinky bone found in Denisova, and so far they’ve sequenced its mitochondrial DNA–that is, the DNA that is housed in mitochondria, sausage-shaped, fuel-producing structures in our cells. The majority of our DNA, which sits in the nucleus of cells, comes from both our mother and father. But mitochondrial DNA all comes from Mom. When the scientists compared the pinky DNA to DNA of humans and Neanderthals, they got something of a shock. If you line up the mitochondrial DNA from any given living human to any other living human, you might expect to find a few dozen points at which they are different. Compare human mtDNA to Neanderthal DNA, and you’ll find about 200 differences. But when the scientists compared the Denisova DNA to a group of human mitochondrial genomes, they found nearly 400 differences. In other words, their DNA was about twice as different from ours than Neanderthal DNA.

The scientists then used the DNA to draw a family tree. Here’s the figure from the paper, which you can also see here for full-size viewing.

full xwoman tree600The Denisova mitochondrial DNA has been passed down, mother to child, on a lineage of hominids that’s separate from the one that produced mitochondria in Neanderthals and in living humans. Paabo and his colleagues estimated the age of common ancestor from which all the mitochondria evolved, based on the mutations in each branch. They concluded that common ancestor lived 1 million years ago. Below is a simple tree that shows the timing more clearly, from an accompanying commentary in Nature.

simple xwoman treeNo matter how you slice it, this is very exciting. All the mitochondrial DNA from living humans is believed to date back just 150,ooo years. That doesn’t mean that we all descend from a single “Eve.” There were other woman around at the time, and they passed down their own mitochondria. But those lineages eventually hit dead ends. In some cases, women only had sons. In others, they never had children. Eventually, all the mitochondrial DNA in the human population could be traced to only one of the women alive at the time.

All the Neanderthal mitochondrial DNA also shares a relatively recent common ancestor of its own–probably thanks to the same process. And now, for the first time, scientists have found hominid mitochondrial DNA that comes from a far more ancient split.

So–how to explain this? A couple possibilities present themselves.

1. The DNA belongs to a species of hominid that’s neither human nor Neanderthal.

This is the most interesting, most science-fictionish possibility.

Our hominid ancestors evolved into upright apes in Africa some six million years ago. By about 1.9 million years ago, some of those hominids had made their way out of Africa and strolled all the way to Indonesia. They go by the name of Homo erectus, and they stuck around Asia for quite a long time–some would argue they were still around 40,000 years ago. Neanderthals appear to have evolved from another wave out of Africa, which spread to Europe and Siberia several hundred thousand years ago. Meanwhile, our own ancestors appear to have stayed put in Africa. The oldest fossils of anatomically modern humans come from Africa 200,000 years ago, for example, and studies on human DNA find that African lineages are the oldest.

The Denisova DNA split too recently from our own to have been carried by H. erectus, the first globe-trotting hominids. But paleoanthropologists have found a fair number of other hominid fossils in Europe and Asia that might belong to more recent waves out of Africa. (Here, for example, is a report on hominids in Europe 1.2 million years ago.) So perhaps there was at least one other wave aside from H. erectus, the expansion of Neanderthals, and the spread of modern humans. If that’s true, this new discovery also means that this wave produced a long lineage of hominids that survived long enough to live alongside humans. We coexisted with yet another species of hominid–along with Neanderthals, H. erectus, and those lovable hobbits, Homo floresiensisfor thousands of years. Our current solitude is a recent fluke.

If #1 turns out to be true, then this DNA deserves a species name of its own. But for now, Paabo and his colleagues have refrained from giving it one. Instead, they’ve nicknamed the source of the DNA “X-woman.” Why the reticence? Probably because of possibility #2…

2. The DNA comes from the finger of a Neanderthal or a human–thanks to a love that dare not speak its name. Imagine, if you will, that an early Neanderthal male takes a morning constitutional in search of woolly rhinos when, gadzooks, he meets up with a fetching X-woman hominid. For whatever reason, the two of them decide to have an interspecies tryst, and X-woman gets pregnant. She gives birth to a girl carrying Neanderthal and X-woman DNA in her nucleus–and nothing but X-woman DNA in her mitochondria. Somehow this girl becomes a part of Neanderthal society; she has Neanderthal children of her own, and they continue to carry the X-woman mitochondrial DNA.

Remember that in every generation, nuclear DNA gets mixed up. Half of the DNA a child carries in the nucleus comes from its father, half from its mother. And with the generation of new eggs and sperm, chromosomes from each parent get chopped up and shuffled back into new combinations. So over generations, the X-woman DNA might gradually dwindle away from the Neanderthal gene pool–but some Neanderthals might still carry X-woman mitochondria, handed down from mother to daughter to grand-daughter.

(It’s also possible that the interbreeding male in this scenario was a human–although just in terms of timing, that’s less likely, since Neanderthals were out of Africa sooner than we were.)

One reason to take this possibility seriously is the fact that other primate species regularly mix up their DNA in just this way. Mongoose lemurs expanded into the range of brown lemurs, for example, and mitochondrial DNA ended up jumping the species barrier. In many cases, the species were separated by a million years or so, just like the Denisov DNA and human/Neanderthal DNA. (This is why it’s hard to use DNA-barcoding to tell closely related primates apart.) Another reason to take this possibility serious is lies in our own genomes. Some scientists have made a forceful case for the presence of ancient non-human DNA in the gene pool of living humans.

Still, even if this scenario turned out to be right, it would mean that a previously unknown X-woman hominid line expanded out of Africa and lived in Asia until relatively recently. Whether that lineage could be rightly considered a separate species of its own is tricky. (For more on that trickiness, see my article, “What is a Species?” from Scientific American.)

I can imagine other possible interpretations, but I’m not sure how plausible they really are. I’ve sent out some queries to some experts, and will add anything interesting I get back [Update: See the end of the post]. Fortunately, it may be possible to rule some possibilities out in just a few months. Paabo and company are busily churning out the sequence of the nuclear DNA from the Denisova pinky. It’s conceivable that the nuclear DNA will be a lot more like human DNA, or a lot more like Neanderthal DNA–making it likely that the fossil belongs to a hybrid. But if the nuclear DNA is just as exotic as the mitochondria, then perhaps the finger bone really does belong to a distinct species that lived 40,000 years ago–a species, it’s worth pointing out, that left its bones behind in the same layer of sediment where Russian scientists have dug up tools and ornaments made of stone and antler.

The possibility of a highly intelligent Siberian Other will have to dance in our heads until more studies come out.

Update: After I posted this, the paleoanthropologist John Hawks offers an alternative explanation on his blog. I followed up with a few questions via email, and based on his post and his reply, here’s my quick distillation:

Maybe the X-woman was not a separate species at all.

Wind back the clock to a million years ago. In Africa, there’s a population of hominids that will eventually give rise to Neanderthals and humans. The Neanderthal lineage expands out across Europe and Asia. They take with them a wide diversity of mitochondria. Most of the studies on Neanderthal DNA have focused on European Neanderthals–and have thus only captured a limited sample of that diversity. Now, in Siberia, Paabo and his colleagues have moved so far from the areas they had studied before that they’re finally getting to other branches of Neanderthal mitochondria.

In this scenario, Neanderthals play a role similar to that of Africans in the diversity of living humans. In Africa, you can find people with genes belonging to very old lineages. The Khoisan bushmen of southern Africa, for example, have genes that branched off from all other human lineages long ago. In other words, the genes of other Africans share a closer ancestor with genes from people out of Africa. Likewise, some Neanderthal mitochondrial DNA is more like human DNA than it is to the Neanderthal DNA found in the Denisova pinky.

[3/27/10: Time to go Borges: an update within an update! The Atavism (which has already displayed great skills in visualization by illustrating my recent reader survey) whipped together a diagram that gets this concept across nicely:

I’ll post more replies as they come in.

Update, 3/25/10 10:15 am: I also got in touch with Laurent Excoffier, a biologist at the University of Bern in Switzerland, who has published models of human evolution indicating that there has been little, if any interbreeding between our own lineage and Neanderthals or other hominids.

Excoffier has argued that some genes that have been claimed to have entered our lineage through interbreeding were actually already present in ancient African human populations. I wondered if the mitochondrial DNA in the Denisova pinky might just be from an old human, not a separate species. Excoffier was skeptical:

This seems relatively unlikely, since it is difficult to understand why this mtDNA lineage would not have been preserved in Africa. Of course some otherwise rare mutations (or DNA sequences) can surf to higher frequencies during range expansions, and this could potentially explain why it could be seen outside Africa and not within Africa. But if that was the case, then it would be difficult to understand why this once frequent sequence would then have disappeared. So, I would thus consider this hypothesis as very unlikely.

I then asked if he thought the best explanation for this DNA was that it came from a separate species, or that it spread from a separate species into Neanderthals or humans through interbreeding.

If this sequence is really true (not an artefact from next-gen sequencing) and if there was no contamination, then a more plausible explanation would be that this sequence comes from a divergent Homo species, as claimed by the authors of the paper.

It is indeed plausible that some non-modern homo or non-Neanderthals roamed in Asia before modern humans spread there, and this sequence could well belong to one of them.

The interesting point for me is that if this sequence is representative of, say, erectus mtDNA diversity in Asia 40-60,000 years ago, then it means that  some divergent erectus were there when modern humans expanded into that region, and that did NOT hybridize with them, or at least not enough to be introgressed by them during their expansion (which is the expectation when hybridization can occur between a local and an invading species).

So there’s a vote for possibility #1.

Reference: Krause et al., “The complete mitochondrial DNA genome of an unknown hominin from southern Siberia” Nature, doi:10.1038/nature08976

CATEGORIZED UNDER: Evolution, The Tangled Bank

Comments (54)

Links to this Post

  1. Others in Siberia? -Gene Expression | March 24, 2010
  2. Update to the X-Woman’s Fingerbone | The Loom | Discover Magazine | March 24, 2010
  3. | Tangible Motion | March 25, 2010
  4. Another Update to X-Woman’s Fingerbone | The Loom | Discover Magazine | March 25, 2010
  5. Is the Mysterious Siberian “X-Woman” a New Hominid Species? | JetLib News | March 25, 2010
  6. Throw another branch of the family tree on the fire. « Communion Of Dreams | March 25, 2010
  7. Links « Evolving Thoughts | March 25, 2010
  8. Possible New Species of Human Discovered - Religious Education Forum | March 25, 2010
  9. Day 004: Thu 25 Mar 2010 at 365 Days of Hell on Earth | March 26, 2010
  10. Linkage 3/24: The Pinky of An Ancestor and Harmful Neurologisms « Science Life Blog « University of Chicago Medical Center | March 26, 2010
  11. Unbekannte Menschenart in Sibirien? « Verschlusssache | March 27, 2010
  12. This Week in Science | Second Reagan Revolution | March 27, 2010
  13. Teaching Science 2.0 » Human evolution… | March 27, 2010
  14. This Week in Science - Online Political Blog | March 27, 2010
  15. Yet Another Update to the X-Woman’s Fingerbone | The Loom | Discover Magazine | March 27, 2010
  16. Zimmer’s evolving blog post on X-woman « Evolving Thoughts | March 27, 2010
  17. The Mysterious Other | Gene Expression | Discover Magazine | March 28, 2010
  18. The Spittoon » Analysis of Ancient DNA Suggests A Previously Unknown Type of Extinct Human Ancestor | March 29, 2010
  19. vastbranch.com - Experience This » Blog Archive » Winning | April 1, 2010
  20. Trial Tuesdays! 001 – Homework | April 6, 2010
  21. Science in the News! 015 – Mystery of the X-Woman | April 7, 2010
  22. A Pinky’s Promise | BEYONDbones | April 9, 2010
  23. Daily Data Dump (Wednesday) | Gene Expression | Discover Magazine | May 12, 2010
  24. YourTechWorld » Daily Data Dump (Wednesday) | Gene Expression | May 12, 2010
  25. Which population is most genetically distant from Africans? | Gene Expression | Discover Magazine | August 18, 2010
  26. Which population is most genetically distant from Africans? | BioLogged | August 18, 2010
  27. Which population is most genetically distant from Africans? | Gene Expression | cYaNk | August 19, 2010
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  1. KJjht

    The x group DNA has been around several years now. There are many of these, usually natives that can’t be figured where they go to the Americas. Most agree that this is interesting, but theories about time and adaptive native x group DNA(faster) are wrong because they appear to been of planet. X woman is a female, so the DNA’s are looking for the same female that found Africa and Europe. This may be difficult if the specific DNA isn’t found in any other human/animal.

  2. Monjur

    This is the best article I have read so far on this topic, namely FOX news, NY Times, Scientific American etc. Thanks!!

  3. You say:
    - “Our hominid ancestors evolved into upright apes in Africa some six million years ago.” This is an assumption without good evidence: 1) The Moroto lumbar vertebra 19 Ma was remarkably human and suggests an upright posture (google “Filler Moroto”). 2) Gibbon locomotion is mostly upright, and gibbons & great apes split c 17 Ma. 3) Sahelanthropus c 7 Ma is called bipedal, but probably predates the H/P split c 5 Ma. IOW, uprightness is probably much older than 6 Ma and is not uniquely human: apparently knucke-walking (in parallel in chimps & gorillas) derived from some earlier sort of bipedalism.
    - “By about 1.9 million years ago, some of those hominids had made their way out of Africa and strolled all the way to Indonesia.” Retroviral data suggest that human ancestors might have been absent from Africa between 4 & 3 Ma (google ” Yohn PLoS”): it is well possible that the Mojokerto Homo fossils in marine sediments at Java were not newcomers there, but had lived there for a few millions of years (eg, at coasts now submerged), and that Homo c 1.8 Ma in Africa was a newcomer from S.Asia.

  4. Gunnar

    A wonderful article about a truly awesome subject.

  5. Gussy Finknottle

    Why is it always assumed that all hominids originated in Africa?

    Why can’t it have been that the X group (if they really are a separate species) and/or the Hobbits and/or even some other group(s) split off from other hominids outside of Africa? Surely this is what happened with, for instance, the other primates (e.g. did the orangutan ancestor originate in Africa and from there spread out to SE Asia or did they evolve into a separate species in SE Asia?).

    Just asking.

  6. MarkD

    Thank you for this article!
    You have no idea how many terrible versions of this there are out there. A few “articles” didn’t even want to use the word mitochondrial DNA. Too complex. So they just call it plain DNA till 3/4 of the way through the article, and then have to explain the difference. And of course the sensationalist headlines.

    Why can’t we make good use of hyperlinks to explain concepts you need an understanding of to even grasp the basics of the story?

    Science journalism is just getting worse out there.

  7. You say:
    - “Our hominid ancestors evolved into upright apes in Africa some six million years ago.”
    This is an assumption without good evidence.
    Uprightness was probably much older, and not confined to human ancestors.
    1) The Moroto lumbar vertebra 19 Ma was remarkably humanlike and suggests an upright posture already some 20 Ma in early hominoids (google “Filler Moroto”).
    2) Gibbon as well as human locomotion is mostly upright, and gibbons & humans split c 17 Ma. It’s well possible that the different locomotions of the great apes (suspensory orangs & knuckle-walking chimps & gorillas) derived from more upright ancestors (upright for whatever reason: hanging from branches, wading in shallow water &/or walking on land).
    3) Sahelanthropus c 7 Ma is called bipedal, but probably predates the H/P split c 5 Ma.
    IOW, uprightness is probably much older than 6 Ma and is not uniquely human: apparently knucke-walking (in parallel in chimps & gorillas) derived from some earlier sort of bipedalism.
    IMO, paleoanthropologists should stop believing that every upright fossil hominoid (including australopithecines) is a closer relative of humans than of other hominoids.
    Google “aquarboreal”.
    You also say:
    - “By about 1.9 million years ago, some of those hominids had made their way out of Africa and strolled all the way to Indonesia.”
    Retroviral data suggest that human ancestors might have been absent from Africa between 4 & 3 Ma (google ” Yohn PLoS”): it is well possible that the Mojokerto Homo fossils 1.9 or 1.8 Ma (found in marine sediments at Java) were not newcomers there, but had lived along South Asian coasts & rivers for a few millions of years (eg, at coasts now submerged), and that instead Homo in Africa was a newcomer from S.Asia.
    Google “econiche Homo”.

  8. I don’t really understand how possibility 2 is different from possibility 1. Both posit the existence of a non-human, non-Neanderthal lineage.

    [CZ: Karen, you're right that both post the *existence* of a non-h/n lineage. However, the question also remains as to which species the possessor of the pinky itself belonged. It's conceivable that 20,000 years earlier, the pinky's possessor's great-great-great-etc. grandfather had a tryst with a non-h/n female, but otherwise, all his or her other ancestors are Neanderthals. One way to think about this is to consider recent arguments in favor of admixture of Neanderthal genes into the human gene pool. If these arguments are right, then there are some Neanderthal genes in circulation right now. But the people who carry those genes wouldn't be considered Neanderthals.]

  9. “The Denisova DNA split too recently from our own to have been carried by H. erectus, the first globe-trotting hominids.”

    That depends on how you define “Homo erectus”. The type specimen is late-occurring and from Java, so a restricted usage of that name could refer only to late Asian/Malayan populations (Java Man, Peking Man, etc.), and not to earlier African/European populations (Nariokotome Boy, Dmanisi Man, etc. — “Homo ergaster” or “Homo erectus ergaster”).

    One morphological analysis found Homo erectus sensu stricto to share more ancestry with the human-Neandertal clade than with Homo ergaster. (Or, if you prefer, found that Homo erectus sensu lato is an ancestral species.) Under this hypothesis, it is possible for the specimen in question to be Homo erectus.

    (Also, if, as some studies suggest, Homo floresiensis branched off before Homo ergaster, even Homo erectus sensu lato might not include the first globe-trotting hominins.)

  10. Aaron Zerah

    Dear Mr. Zimmer: Thank you so much for this clear and elegant exploration of the possible “meaning” of this new discovery. I think we should no longer be amazed to find that “our” history is more ancient, complex, and diversified than we have previously understood or believed. We humans (of all kinds) are a strange and mysterious lot!

    In my upcoming book, I call us The Sacred Ape because spiritual inquiry and expression seems to be our most compelling and distinctive feature. It’s found in Neanderthal burials and prehistoric Homo sapiens’ use of symbols, and I’m not surprised to hear that bracelets and other “decorations” were discovered in the surrounding layers around the Demisova child. A closer look at the map you provided (thank you) reveals that these people lived at the very heart of the “Old World” and the epicenter of a shamanic tradition and culture that still lives powerfully today.

    I, like you, look very much forward to the further (and hopefully conclusive) results of genetic testing. The “proof” of either of the two main hypotheses you outlined would provide fascinating insight into our place in the world. One thing we know for certain is that as special as we are to be the only (we believe) human species alive today, we must balance our self-appreciation (and perhaps at times overly zealous self-congratulation) with humility and wonder.

    In kindness,

    Aaron Zerah

    P.S. What do you think about the possibility (as offered by geneticists at MIT and others) that hominins and chimpanzees interbred and that we are descendants of that hybrid

  11. I know Paabo is very good with ancient DNA, but any chance the highly divergent sequence is due to degradation/contamination?

  12. Monkey

    Excellent coverage, still too early to define though. Keep on it, Carl!

  13. Beckmesser jr.

    You wrote:
    “There’s good evidence of Homo sapiens in the region for at least 40,000 years, and Paabo and his colleagues have also isolated 30,000-year old DNA from Siberian sites that is similar to the DNA from Neanderthals in Europe.”….”The scientists then used the DNA to draw a family tree. Here’s the figure from the paper, which you can also see…”

    Just wondering why they don’t include this ‘similar’ Neanderthals mtDNA from Siberia in their family-tree?

  14. strangetruther

    What’s surprising about the Caucasian finger is that people were surprised. If we accept that Heidelbergensis, if the term pleases you, was present under suitable conditions from western Europe to western Asia at say half mya give or take, and was simultaneously spawning the lines to Neanderthals and moderns, but in Africa, then the European Heidelbergers would not have been ancestral to either Neanderthals or moderns, except through interbreeding with the African arrivals. A million year old mitochondrial split between the African and European Heidelberg branches is not surprising, and could appear between say Neanderthals and any surviving descendant of the likes of Boxgrove.

    Actually I wasn’t surprised that people were surprised, seeing as how shocked they were by Ardi’s revelation last October that the human-chimp ancestor was upright when the lineages split, even though this theory had not just been on the cards for years but explained the evidence best, and should have been compulsorily considered in journal articles instead of being invisibled along with its early proponents. I predict people will be even more surprised when they finally twig that chimps are from Lucy but we aren’t (but are instead from the Kenyanthropus lineage) and that gorillas are from a line of robust “australopithecines” that weren’t actually australopithecines. The lesson is simple. Don’t choose your theory until you’ve laid out the entire space of potential theories, in your mind or even on paper, and then select the theory that explains the evidence best, not necessarily the theory which you think, even subconsciously, will avoid criticism.

    On the Caucasian finger though, John Hawks’ comment this week (http://johnhawks.net/weblog) that a million year split can appear between mammoths of the same species, and even in the gene trees of chimps, may be a slightly different way from mine of referring to the same evolutionary events.

  15. strangetruther

    Quoting Laurent Excoffier:
    “It is indeed plausible that some non-modern homo or non-Neanderthals roamed in Asia before modern humans spread there,…”

    There’s no point referring to view as well-established as that, as if it’s something we might like to start considering.

    “…if this sequence is representative of, say, erectus mtDNA diversity in Asia 40-60,000 years ago, then it means that  some divergent erectus were there when modern humans expanded into that region, and that did NOT hybridize with them…”

    Other evidence may suggest we did not hybridise with Asian erectus (though I believe there’s evidence that suggests we did), but how you can use non-combining mitochondrial evidence against hybridisation is beyond me.

  16. John Jackson

    Quoting Laurent Excoffier:
    “It is indeed plausible that some non-modern homo or non-Neanderthals roamed in Asia before modern humans spread there,…”

    There’s no point referring to view as well-established as that, as if it’s something we might like to start considering.

    “…if this sequence is representative of, say, erectus mtDNA diversity in Asia 40-60,000 years ago, then it means that  some divergent erectus were there when modern humans expanded into that region, and that did NOT hybridize with them…”

    Other evidence may suggest we did not hybridise with Asian erectus (though I believe there’s evidence that suggests we did), but how you can use non-combining mitochondrial evidence against hybridisation is beyond me.

  17. John Jackson

    What’s surprising about the Caucasian finger is that people were surprised. If we accept that Heidelbergensis, if the term pleases you, was present under suitable conditions from western Europe to western Asia at say half mya give or take, and was simultaneously spawning the lines to Neanderthals and moderns, but in Africa, then the European Heidelbergers would not have been ancestral to either Neanderthals or moderns, except through interbreeding with the African arrivals. A million year old mitochondrial split between the African and European Heidelberg branches is not surprising, and could appear between say Neanderthals and any surviving descendant of the likes of Boxgrove.

    Actually I wasn’t surprised that people were surprised, seeing as how shocked they were by Ardi’s revelation last October that the human-chimp ancestor was upright when the lineages split, even though this theory had not just been on the cards for years but explained the evidence best, and should have been compulsorily considered in journal articles instead of being invisibled along with its early proponents. I predict people will be even more surprised when they finally twig that chimps are from Lucy but we aren’t (but are instead from the Kenyanthropus lineage) and that gorillas are from a line of robust “australopithecines” that weren’t actually australopithecines. The lesson is simple. Don’t choose your theory until you’ve laid out the entire space of potential theories, in your mind or even on paper, and then select the theory that explains the evidence best, not necessarily the theory which you think, even subconsciously, will avoid criticism.

    On the Caucasian finger though, John Hawks’ comment this week (http://johnhawks.net/weblog) that a million year split can appear between mammoths of the same species, and even in the gene trees of chimps, may be a slightly different way from mine of referring to the same evolutionary events.

  18. John Jackson

    Congratulations Zimmer! By pointlessly blocking my main comment here, you’ve demonstrated yet again that you disapprove of any scientific insight that doesn’t show abject servility to those you want to stay on the good side of.

    You’re not “doing good science” by this, you’re not propagating an understanding of what good science is, and above all, you won’t be blocking my message, which will now of course give you the featuring role you so richly deserve.

    [CZ: Spare me the theatrics. Your comments were automatically held for moderation. Their time stamps show they came in an hour ago. I just sat down this morning and started approving comments that came through overnight. Then I came across this one. Frankly, I was too busy sleeping to play the part of the censor you imagine for me.]

  19. John Jackson

    Since there was a misunderstanding, sorry. However your blogging software sometimes told me posts were being held for approval, sometimes removed them after initially displaying them and sometimes just printed them as though they had been accepted. I know you’re not fully responsible for every detail of operation of the system you use, but I have to say it doesn’t do me any favours either. And I still claim your record of interpreting and portraying the scientific theoretical landscape in all the areas I know anything about, is unbalanced.

  20. maelstrom

    search “Almas” + “Altai” for an anomalous hominid in modern times.

  21. [...] years ago. This population is a sister lineage to the various Eurasian hominins, Neandertals, X-woman, [...]

  22. Cal King

    In science we tend to favor the simplest explanation, which is of course not necessarily correct. Regardless, the simplest explanation is that this X woman was a member of Homo erectus. It is slightly younger than the oldest H. erectus in Asia, but not by much. There is no reason to believe that human migration is a series of all or nothing square waves. Africans first left Africa, say, 60,000 years ago, but the migration has ever stopped since the first wave. And it continues to this date.

  23. Sean

    “1. The DNA belongs to a species of hominid that’s neither human nor Neanderthal.”

    Neanderthals are human. You mean neither Homo sapiens nor Homo neanderthalensis.

  24. [...] Carl Zimmer – Mar 24, 2010 – The X-Woman’s Fingerbone [...]

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The Loom

A blog about life, past and future. Written by DISCOVER contributing editor and columnist Carl Zimmer.

About Carl Zimmer

Carl Zimmer writes about science regularly for The New York Times and magazines such as DISCOVER, which also hosts his blog, The LoomHe is the author of 12 books, the most recent of which is Science Ink: Tattoos of the Science Obsessed.

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