Dendro Dissidents

How long ago was the time of Emperor Augustus? Most educated people, including professional historians and archaeologists, will reply “about 2000 years” if you ask them. But a considerable number of amateur dendrochronologists say “about 1800 years“. And because of an unfortunate peculiarity in how professional dendrochronologists work, it is very hard to convince these dissident amateurs that they are wrong. Because they’re actually thinking straight given the data available to them.

If you look at published dendro curves for the transalpine provinces of the Empire, you find that they contain two main blocks of information covering the past 2500 years or so. There’s one that extends solidly from today and back to about AD 400, consisting of many tightly interlinked samples. And then there’s a Roman-era block that is also quite solid internally. But between the two blocks is a period of about 200 years when there are very few samples. It appears to be hard to find preserved timber that grew in the 3rd and 4th centuries AD. There are enough samples to satisfy professionals that they actually have the whole 2000 years covered, but the sample overlaps for the gap between the blocks are few and rather weak.

Professional dendrochronologists explain this lack of finds by reference to the cessation of Roman building projects and to deforestation during the Imperial centuries. According to the accepted model, the reason that there are so few samples covering the gap between the blocks is that few trees were of a suitable age for construction timber during that time and even fewer were used to build anything that has been preserved. Trees that fell into bogs and rivers at the time would have too few rings to be of much use to dendrochronology.

Dissident amateurs instead think that the Roman block and the recent block have been joined incorrectly, and that there shouldn’t be any gap at all between them in the diagrams. According to them, the professionals have been fooled by the early historians Dionysius Exiguus and Beda Venerabilis into thinking that the Western Empire fell 1600 years ago, using this as an axiom in their work with the dendro curves, when in fact it happened only 1400 years ago. A common idea about why this should be so is that the Church of Rome added a couple of centuries to its age to gain legitimacy: in other words, a conspiracy of early historians.

I mentioned published dendro curves. The rub here is that most dendro data are never published. They are kept as in-house secrets in dendro labs in order for these to be able to sell their services to archaeologists. So when the amateurs challenge the professionals’ opinion, all the latter can reply is “We know we’re right but we can’t show you how we know”. And that is of course an unscientific approach to the issue. The amateurs rarely get access to 1st Millennium wood samples, and basically have to work with the past 1000 years in their own studies. And so they cultivate a dissident opinion that could swiftly be laid to rest — or be accepted as fact — if wood samples and measurement databases were only made public.

My guess, though, is that any Roman archaeologist could solve the controversy quite easily, perhaps even using published radiocarbon dates. All you need are a couple of well-sourced dates for contexts known to be from about the time of the first emperors, such as Pompeii. (But if you know that a context is from that time, then you have very little reason to pay for radiocarbon dating.) Because although the calibration curve for radiocarbon depends on dendrochronology, several of the available datasets are not from European wood samples. And there is of course no inherent bias about where on the diagram the fall of Rome should be in North American dendrochronology, for instance.

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17 thoughts on “Dendro Dissidents

  1. Many years ago, I saw a similar claim regarding the years just before 1000. It was some german historian who said that Charlemagne was a myth created by some monarchs who wanted a noble ancestor to claim descent from and deliberately miscounted the years to reach the magic 1000. Sorry my memory is so fuzzy.

    I thought it could be resolved pretty conclusively using astronomical events, particularly eclipses. Those are widely recorded, and predictable (forward and back) with considerable accuracy.


  2. Interesting. This a conspiracy I’ve never heard of. It’s vaguely reminiscent of something I heard some years back, that the Dark Ages are ‘dark’ in terms of few to no records due to never having taken place. Some ruler (I don’t recall who) should supposedly have been so keen on the Millennium happening during his rule that he simply added 3 centuries to the calendar, going straight from the 700s to the 1000s.

    I wonder how long it’ll take before the AGW denialists latch onto this conspiracy as well. The proprietary datasets are sadly all too akin to temperature databases. (Yes, I do realise that only a few datasets have in reality been withheld.)


  3. Um, if that dendrochrinology data isn’t published and isn’t available, then how is it ever used in research? “according to data I can’t show, and haven’t in fact even seen myself, the date is …”. Just a little facetiously, why aren’t papers relying on that secret data rejected out of hand by reviewers up and until they can fill out this crucial point with a proper reference?


  4. Archaeologists trust an osteologist to be able to identify a cow femur. And we trust a paleobotanist to be able to identify a birch seed. And we know the principles of dendrochronology. We don’t actually want to do dendro work ourselves. That’s why few professionals complain about proprietary data and black-box analyses in dendrochronology.


  5. My department recently got sent a glossy set of self-published books by a Hungarian missing-years theorist who has a special view all of his own, I need to come up with an excuse to blog those, they’re great. Utterly mad but inspired self-publicity. Apart from the ethical problems it must be a fun way to make a living. But yes: the simple answer is to put dendro next to radio-carbon, or indeed maybe this new ceramic rehydroxilation method, and assuming they all roughly line up… Of course, since they are to some extent tested against each other in development, there may still be problems enough for weasels to hide in, but it’s a start.


  6. > Some ruler (I don’t recall who) should supposedly have been so keen
    > on the Millennium happening during his rule that he simply added 3
    > centuries to the calendar, going straight from the 700s to the 1000s.

    Emperor Otto III, but the story is nonsense. Otto was little more than the mayor of Rome, and even there his hold on power was tentative at best, when he refused to plunder the rival town of Tivoli, the Romans chased him away. He would have been unable to impose his will on Byzantine, Muslim or Sung Chinese historians or chroniclers. Otto also was a staunch classicist, so he would have used the dating from the foundation of Rome (AUC era) rather than the Christian AD era anyway.


  7. Reference to recorded astronomical events should settle the matter. For either side.

    (I mean if the dissidents are right they can slam-dunk their argument by referring to astronomy, just as easily as the establishment can if they’re right)


  8. The Russian Anatoly Fomenko takes the whole ‘missing years’ thing a step or two farther, claiming that most of history before 1400 is simply the same overlapping chronologies, spread apart and with the names changed for different cultures. There’s a lot of matching lists of Popes’ reigns to Roman Emperors’, and claiming that Charlemagne and the biblical Joshua were the same person, among other silliness.

    Sounds crazy until you realize how much we depend on Scalinger’s 16th-century chronology as a basis for historical dating. Well, it still sounds crazy after that too, but does make you think a bit.


  9. -Surely the occasional big volcanic eruption will create a “signal” in the tree rings that extends across all regions and continents?
    That way, if there is a gap in the tree ring record in the former Roman empire, you just need to identify volcanic eruption effects on the atmosphere mirrored in the tree rings on either side of the gap, and thus get an absolute chronology instead of a “floating” one.


  10. “volcanic eruption will create a “signal” in the tree rings that extends across all regions and continents?
    That way, if there is a gap in the tree ring record in the former Roman empire, you just need to identify volcanic eruption effects on the atmosphere mirrored in the tree rings”

    Sounds like a good idea, and this phenomenon is described in the litterature, e.g. by Mike Baillie in his book “A slice through time”. Though when we look at the Hollstein data as we have retrieved it from his book we cannot see anything special with e.g. AD 540 which Baillie claims is a year of disaster. Maybe that type of volcanic events have a strong influence on trees living in an exposed position, but not on oaks living in the Trier region in Germany. Though if the Hollstein data is corrupt within the Carolingian time (with little data), what we think is a tree ring of AD 540 is instead a ring of say AD 620. Though there is no other extreme point within the Hollstein data though we think that we have built it back to AD 410. (Then comes the gap before the Roman time data.)


  11. This reminds me of some of R. A. Lafferty’s work. In “What’s the Name of That Town?” an odd AI figures out, and attempts to convince its human colleagues, that a chunk of history was so traumatic that people have wiped it from their memory.

    And, not having my library handy, I can’t remember if that’s the same story in which he speculates on large chunks of history being forgotten and combined: for example, three U.S. presidents named John Adams, not two.


  12. In my opinion there are now free dendro material available to validate the commonly accepted bridge, although still rather weak. I wrote a text about it here. Despite those evidences, someone among us may still not be fully convinced. So trying to get the institutions to release the samples which may turn out to be the final prof goes on…


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