The Black Death (plague) is still a mystery, still not explained - blog by Gurdur

 




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The Black Death (plague) is still a mystery, still not explained
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Posted 16-Oct-2011 at 06:14 PM (18:14) by Gurdur
Updated 16-Oct-2011 at 06:28 PM (18:28) by Gurdur

There's been a fair bit of news over the last two months about studies into the Black Death, that epidemic of the 14th century (mainly between 1347 and 1353 AD). The good news is that the studies appear to add to our knowledge. The bad news is that they contradict each other.

First off, usually the Black Death is blamed on plague, Yersina pestis, and more specfically, on one form of the illness that Yersina pestis can cause, bubonic plague. It can also cause pneumonic plague (spread through the coughs of a sufferer) and septicemic plague, when it gets widespread in the victim's blood.

Bubonic plague can imitate many other illnesses, and the only true clue is the presence of buboes, great big and very painful swellings of lymph nodes which often turn blackish, and are usually in the groin in the case of the plague. The word bubo comes from the Greek boubôn, meaing "groin". Modern bubonic plague is usually carried by fleas and rats; fleas from rats rarely bite humans above the ankle, and the lymph nodes in the groin are the first reached by Yersina pestis. Everyone is often taught it's the triad of Y. pestis, the Black Rat (Rattus rattus) and the flea responsible for the plague - and also for the Black Death of the 14th century, though that looks to be wrong.

Now, there was fairly recently a study by Gilbert and Thomas et al (2003) that simply could not find any evidence of Y. pestis in the skeletons of what were supposed to be 14th century plague victims from several plague pits - 66 victims from 5 mass graves, which is a considerable body of evidence, or bodies of lack of evidence.

There are some myths about the Black Death; while spread of infection was amazingly fast and lethality rates grossly high (and far higher than even untreated plague today), quite often Black Death victims were still buried relatively carefully and not too haphazardly, as shown in the photo just below, shown in Gummer, 2010. In that you can see the skeleton of someone who would have been well-off; the black around the carefully laid-out skeleton is from charcoal, used to line the person's coffin. Next to that skeleton is the skeleton of someone simply tossed into the mass pit next to the other coffin (shown by the position of the bones), and on the other side is the skeleton of a child, tossed in to fill the space between adults. Yet despite the evidence this is a mass burial site, a hasty plague pit, the bodies have still been carefully laid in position according to the religious mores of that time.


Then there's a very recent study (2011) by archeologists working in London that cannot find the necessary evidence to blame rats; there just aren't enough rat skeletons around. Moreover, the medieval evidence doesn't point to rats, either. There's even more evidence to hint that Yersina pestis was not the primary culprit in the Black Death. Susan Scott and Christopher Duncan (2001) kicked the rat hypothesis; George Christakos et al (2005, 2007) showed the Black Death simply didn't look or act at all like the modern plague. Let's look at some of the evidence, much of which is cited handily by Gummer, 2010:

modern plague
The Black Death
Primarly carried and harboured by rats Simply not enough rats around, dead (archeological) or alive (no medieval reports of rat plagues at the time of the Black Death, for example). Plus rats cannot move at the speed of the spread of infection of the Black Death.
The spread of infection of bubonic plague in a relatively modern epidemic in India moved as slowly as fifteen metres per week - and that in the presence of modern railroads and roads. Speed of spread of the Black Death was up to 5 kilometres a day.
Modern bubonic plague has a lower mortality (untreated) than the Black Death The Black Death seems to have had an overall mortality rate of 50%, with up to 100% in some places.
There is no immunity gained through having survived the modern plague. The medieval sources very often point to survivors being immune to subsequent waves of the epidemic.
Modern bubonic plague has an incubation period of up to 6 days The Black Death had an incubation length of up to one month (cited in Gummer, 2010).
Buboes in groin only Buboes in groin, neck, armpits etc.

So why the differences? It could be surmised that there had been plasmid change, mutation, in Yersina pestis, causing the differences; except Schuenemann et al (2011) showed no plasmid difference between medieval and modern Y. pestis. Damn. Then in a very intelligent reflection, the blogger ERV mooted that the genetic mutation could have been in and through a viral phage infecting the Y. pestis bacteria. This was a great suggestion; only trouble was, up pops a new study by Bos et al (2011) mapping the Yersina pestis genome, and showing no real differences of any significance at all. Oooops and damn, damn, damn, as ERV also wrote about.

Then that study by Bos et al (2011) also does phylogenetic analysis to suggest strongly that Yersina pestis emerged in its form sometime around the 14th century. I.e., it wasn't around back much before then, in any recognisable form. OK ...... except then there's yet another study, by Wiechmann & Grupe (2005) (with thanks for the heads-up to @rmathematicus, passing along from the Contagion blog) claiming to find Y. pestis in two skeletal remains, of an adult woman and a young girl, in a cemetary dating back to the 6th century AD.. Which would make Y. pestis responsible for the Justinian Plague of the 6th century. And therefore strongly suspect for the medieval Black Death. Oh, except the epidemological details still don't fit. Then many try suggesting malnutrition etc. as being responsible for the differences; except they also had malnutrion in the Indian plague, and no such differences were observable, except malnutrition often existed in the Middle Ages without the Black Death, and many well-fed people also died like flies very quickly from the Black Death. Meh.

We're not getting much anywhere, and that fast, no? Looks like the Black Death is still very much a mystery, and it's going to stay that way a fair while.




Gilbert, M. Thomas P. et al. (2003). "Absence of Y. pestis-specific DNA in human teeth from European excavations of putative plague victims" . Society for General Microbiology – 153rd Meeting, 2003.

Wiechmann I, & Grupe G (2005). "Detection of Yersinia pestis DNA in two early medieval skeletal finds from Aschheim (Upper Bavaria, 6th century A.D.)". American Journal of Physical Anthropology, 126 (1), 48-55 PMID: 15386257

Scott, Susan, and Duncan, Christopher J. (2001), "Biology of Plagues: Evidence from Historical Populations", (Cambridge: Cambridge University Press 2001)

Scott, Susan, and Duncan, Christopher J. (2004), "Return of the Black Death: the World's greatest serial killer", (Chichester: Wiley, 2004)

Christakos, George and Olea, Ricardo A. (2005), "New space-time perspectives on the propagation characteristics of the Black Death epidemic and its relation to bubonic plague", Stochiastic Enviromental research And Risk Assessment, vol. 19 (2005)

Christakos, George; Olea, Ricardo A.; Serre, Mark L.; and Yu, Hwa-Lung (2005), "Interdisciplinary Public Health Reasoning And Epidemic Modelling: The Case Of The Black Death", (New York: Springer, 2005)

Christakos, George; Olea, Ricardo A.; and Yu, Hwa-Lung (2007), "Recent results on the spaciotemporal modelling and comparative analysis of Black Death and bubonic plague modelling", Public Health, vol. 121 (2007)

Gummer, Benedict (2010), "The Scourging Angel: The Black Death In The British Isles", (London: Vintage Press, 2010)


        


              

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  1. Old Comment
    ouinon's Avatar
    You say that malnutrition ( by which I assume you mean "not enough food", rather than "toxic/noxious/debilitating food"? ) doesn't correlate ( present when plague absent and/or the rich also caught the plague etc ) ... but has anyone looked for a correlation between plague activity/virulence/mortality rates and a couple of huge dietary changes which took place in Europe between 500 and 1400 AD, ie. the introduction of crystallised sugar from India and the Middle East during and after the Crusades ( 1100 onwards ) AND the nearly concurrent and dramatic increase in consumption of cereals, especially wheat in the form of bread, ( replacing an orginally mainly meat, dairy and vegetable-based diet, first of all by barley-thickened "stews" and oat porridges etc and then by bread )?

    A similar huge die-off occurred in the Middle East, or "Fertile Crescent", in a very short period after the neolithic revolution took off, precisely as wheat consumption spread through out that area, and another one in India when the cultivation of wheat arrived there.

    Very often the "real" cause/critical factor in a "plague" needn't be, isn't in fact, a bug/bacteria/virus, so much as an environmental one making a population suddenly more vulnerable.

    Someone in the world of alternative/complementary medicine once said that the body is like the earth, or soil, and bacteria/viruses like seeds ... which only grow dangerously if the soil is "poor".

    NB. A bit of basic history about the introduction of wheat, ( but without all the dietary information, specific effects, etc that I have been reading about for the last 18 years! ):

    From Wikipedia on "Medieval Cuisine": "The period between c. 500 and 1300 saw a major change in diet that affected most of Europe. More intense agriculture on an ever-increasing acreage resulted in a shift from animal products, meat and dairy products to various grains and vegetables as the staple of the majority population.[36] Before the 14th century bread was not as common among the lower classes, especially in the north where wheat was more difficult to grow. A bread-based diet became gradually more common during the 15th century and replaced warm intermediate meals that were porridge- or gruel-based. Leavened bread was more common in wheat-growing regions in the south, while unleavened flatbread of barley, rye or oats remained more common in northern and highland regions, and unleavened flatbread was also common as provisions for troops.[15]"

    The profound effects of wheat, ( and glutenous grains in general ), and of sugar, ( a concentrated crystallised acid, which the arabs used by the "grain" as an anaesthetic, like opium, for surgical operations when they first discovered it ), on health should not be underestimated.
    .
    Posted 16-Oct-2011 at 09:38 PM (21:38) by ouinon ouinon is offline
    Updated 16-Oct-2011 at 09:45 PM (21:45) by ouinon
  2. Old Comment
    ouinon's Avatar
    PS. Something to look for would be evidence that certain groups or communities or individuals unexpectedly escaped or resisted infection despite likely exposure to it, and that those groups or individuals did not eat wheat/glutenous cereals and/or sugar ( whether because of personal taste, way of life, access to these foods, etc ), and other groups/individuals unexpectedly succumbed to it:

    eg. some rich people may have eaten a lot of both because white flour bread and sugar were "fashionable" and relative luxuries at that time.

    eg. some/many poor may have eaten the cheaper/more common glutenous cereal barley, or in some parts of Europe rye, or "brown"/unrefined wheat etc and succumbed, but other poor people still on more traditional diets, meat, veg, eggs, dairy, etc not become victims.
    Posted 16-Oct-2011 at 10:10 PM (22:10) by ouinon ouinon is offline
  3. Old Comment
    But ouinon, presumably people were more likely to get ill if they were in the proximity of someone who was ill with the mystery disease, probably indicating that it was something infectious.

    I wonder whether it could have been a particularly virulent airborne strain of staphylococcus aureus or something similar?

    Savi Hensman
    Posted 16-Oct-2011 at 10:28 PM (22:28) by Unregistered
  4. Old Comment
    Gurdur's Avatar
    Quote:
    Originally Posted by Unregistered View Comment
    But ouinon, presumably people were more likely to get ill if they were in the proximity of someone who was ill with the mystery disease, probably indicating that it was something infectious.

    I wonder whether it could have been a particularly virulent airborne strain of staphylococcus aureus or something similar?
    Savi Hensman
    The medieval accounts often lay great stress on direct person-to-person infectivity; and bubonic plague is not directly infectious person to person. Interesting, no?

    Current theories include pneumonic anthrax (bacterial), and Ebola fever (viral), or something similar to Ebola. Given the incubation length, I'm leaning towards viruses like Ebola myself.
    Posted 16-Oct-2011 at 10:41 PM (22:41) by Gurdur Gurdur is offline
  5. Old Comment
    Gurdur's Avatar
    Quote:
    Originally Posted by ouinon View Comment
    ... The profound effects of wheat, ( and glutenous grains in general ), and of sugar, ( a concentrated crystallised acid, which the arabs used by the "grain" as an anaesthetic, like opium, for surgical operations when they first discovered it ), on health should not be underestimated.
    .
    While true, ouinon, such effects typically take a good deal of time to show up. Very rarely is there a direct, speedy effect like this; and poor people died like flies too, and they would have had no access at all to sugar except in honey. Coeliac disease (gluten sensitivity) is unlikely to play much role in a majority of the population at any time, and the Black Death had an average 50% mortality rate often.
    Posted 16-Oct-2011 at 10:44 PM (22:44) by Gurdur Gurdur is offline
  6. Old Comment
    ouinon's Avatar
    I obviously didn't express myself very clearly.

    I am not suggesting that wheat or gluten intolerance and/or the various degenerative diseases ( diabetes, thyroid disorders, neurological diseases, etc ) with which gluten is increasingly correlated, nor the longterm effects of sugar alone ( many serious ones ), were directly responsible for the deaths, but that the increased exposure of a large population to gluten ( and to sugar in the richer groups ) made them extremely susceptible to any or perhaps particular bacteria/viruses in their environment, that disease spread especially fast, was unusually virulent, because the population had not been exposed to gluten ( or sugar ) for long enough to have weeded out those most affected by gluten etc. ie. Wheat was a ( relatively ) newly arrived "stress" on the population's gene pool, and the gradual effect on "constitutional" resistance/strength, including that of infants/children through the epigenetic processes in the wombs of women in gluten-compromised health, meant that *all* bacteria/viruses had a field day.

    Records from the "Fertile Crescent" show that in a short period after the introduction of agriculture, and the systematic consumption of glutenous grains, there was a massive die-off of a large percentage of the population, those who were particularly senstive to gluten's effects on their bodies succumbed to diseases and died like flies, most of them in their infancy/pre-reproductive age, ( exactly as happened in the Plague ), such that the prevalence of certain genes in the population changed significantly, ie. fewer people with the genes responsible for a gluten-reaction ( in fact you can trace the length of time that a population has been farming wheat by the percentage of the pop that has the gluten-sensitive genes; the % increases the further away from the fertile crescent you go! ).
    Posted 16-Oct-2011 at 11:07 PM (23:07) by ouinon ouinon is offline
    Updated 16-Oct-2011 at 11:54 PM (23:54) by ouinon
  7. Old Comment
    ouinon's Avatar
    PS. Classic coeliac disease may "only" be present in 1% of the modern European population, and gluten-intolerance in "only" 5%-15% ( even -30% if include non-autoimmune reactions like increased/hypersensitive intestinal permeability reactions to substances in gluten/plant storage proteins generally, or the lectins which protect them ), depending on which studies you believe, but this percentage ( 1% to 15% of varying levels of reactivity ), would have been a lot higher before the European population was exposed to gluten ... and the degenerative effects are cumulative, ... recent studies are discovering that a parent's physical health/illnesses and diet in their pre-childbearing lifetime have an effect on the *genetic* makeup of their children.

    PPS. And apparently the 1348 Plague was preceded by a mysterious blight on farm animals, killing off huge numbers of cattle and sheep in much of Europe, such that when a, or several, new "bacteria" arrived there were a lot of people eating more glutenous grains ( or even eating them for the first time ) than might have otherwise been the case.
    Posted 16-Oct-2011 at 11:14 PM (23:14) by ouinon ouinon is offline
    Updated 16-Oct-2011 at 11:54 PM (23:54) by ouinon
  8. Old Comment
    ouinon's Avatar
    Ok, just realised why/how we might be at cross-purposes here. I am interested in/exploring a reason why *a* plague of any sort may have hit Europe at this point, whereas you are looking at what bacteria in particular it may have been.

    I think that it may have been a huge mixture of many, different if related, ones, to which the European population suddenly became hopelessly vulnerable after a certain critical number of generations had been eating gluten/cereals, ( and the rich had been eating sugar ), and/or a critical threshold/level of consumption had been reached, and that although the most dramatic, and most memorable, symptoms were of bubonic etc plague, many of the dead/ill were actually victims of other, if related, diseases. ... ie. the massive widespread "plague" effect was not caused by one bacteria, but by the state of health of the population in general at that time.
    Posted 16-Oct-2011 at 11:48 PM (23:48) by ouinon ouinon is offline
    Updated 16-Oct-2011 at 11:55 PM (23:55) by ouinon
  9. Old Comment
    ouinon's Avatar
    Final PS!

    And if the only common symptom, if there really was one, was the swollen discoloured glands ... then it is possible that many people were especially susceptible to the kinds of illness/bacteria which directly attack the immune-system glands, ( rather than other organs ), because gluten, entering by the intestines, having triggered the intestinal membrane to become unusually permeable, such that cannot vomit it out, or use other first-resort defences, ( skin, etc ) but must instantly use the glands, ( in those genetically sensitive to it ), would have exhausted, or over-excited/*inflamed* precisely those parts of the body ... they would have been suffering from a sort of "chronic" illness simply from eating gluten.

    I realise that it's a bit of a shock thinking of wheat in this way, as a massive environmental "assault", but that is what it seems to have been for a surprisingly large percentage of the human population, ( and still is for some ), such that great swathes of people die off within a few generations of being exposed to any significant quantities of it, the general debility/weakness it produces causing fatal susceptibility to a wide range of disease ... Just wondering now about the history of the Amazonian Indian civilisation which completely disappeared between one visit from Europeans introducing wheat to them, and another visit a few decades later.
    Posted 17-Oct-2011 at 12:09 AM (00:09) by ouinon ouinon is offline
    Updated 17-Oct-2011 at 12:16 AM (00:16) by ouinon
  10. Old Comment
    ouinon's Avatar
    ... And there may have been a large part of nocebo involved too!

    Thinking about the ripple-effect of gluten, ( largest protein molecule we ever eat by far; very recent "arrival" on our planet after a highly unusual sort of mutation in 15,000BC in plants growing in Iraq/NE Turkey; rare in that it contains opioids, *plus* the chemical signal which opens the "tight junctions" between our intestinal-membrane-cells such that the whole opioid-proteins are allowed to pass into the blood and to the brain ), .. and how China appears to have suffered a similar huge plague a little before Europe ( perhaps also following the increasing use of wheat ).

    Thinking of a slow "ripple" with its epicentre in the Fertile Crescent, an effect measured in generations, perhaps seven, with further compound impacts on the body after seven times seven generations would that take us up to the Spanish Flu? ...

    Anyway, getting serious again ... I realised on waking this morning that your blog was really about looking for a fascinatingly mysterious unidentified single bacterial/viral bad-guy, but what I thought was most interesting was that scientists are not finding any evidence that the mass die-off was caused by any one single bug ...

    And what if in addition to the suddenly/acutely debilitating effect of a certain number of generations of consuming gluten plus a sudden vastly increased number eating it as a result of the mysterious deaths of cattle and sheep ( 20 years before ... might that have had something to do with feeding them on wheat? ) ... there was a nocebo effect involved?

    What if people *believed* that there was an absolutely virulent and absolutely fatal disease at large and died like flies even when all they had was a sort of flu or similar non-life-threatening disease? The food opioids in gluten being consumed in larger and larger quantities by more and more people, ( plus rye-ergot effects in places during unusually wet and cold periods ) could have contributed to a sort of mass-hysteria in which the slightest sneeze, or rash or cough, or enlarged gland, or tiny bump ( "The Secret GArden" springs to mind! ), caused people to believe that they had caught the dreaded "thing" and die.
    .
    Posted 17-Oct-2011 at 08:20 AM (08:20) by ouinon ouinon is offline
    Updated 17-Oct-2011 at 08:29 AM (08:29) by ouinon
  11. Old Comment

    archaeologist's stories and hard science

    Nice compilation of the inconsistecies of The Black Death story.

    Kirsten et al certainly adds to the evidence that Y.pestis was present in the urban centres of Europe during the crisis years associated with The Black Death, so the question is if Rat borne disease wasn't resonsible for the extensive spread of disease in the 'plague years' was pneumonic plague sufficiently transmissable or were other factors required to produce the recorded death rates ?

    I'm not sure that the Aschheim material provides strong enough evidence to argue against a Y.pestis emergent date in the 14thC. Even if the Aschheim skeletons were from a secure context (cemetaries usually produce messy archaeology), and even if C14 dating accorded a high probability of death contemporary with the associated archaeology, just two skeletons from a single location isn't scientifically strong evidence. What's good enough for an archaeological assessment of a single excavation, is rarely sufficient for a hard science extrapolation. Of course if other 6th and 7thC sites yield evidence for Y.pestis then an earlier emergent date would become more likely but at this state of knowledge a 14thC date seems more strongly evidenced.

    The absence of Y.pestis in skeletons from a number of European plague pits dated to the the Black Death years clearly suggests at least one other lethal communicable disease was in play. The presence of a second disease is not surprising as social collapse resulting from an initial population decline would likely have seen a breakdown in food production and distribution, resulting in nutritional stress and associated vulnerability, while population perturbation may also have increased communication of disease in ways not previously seen. These effects may well have engendered a variety of feedback loops in which social and economic responses served to heighten the lethality of the crisis far beyond the clinical effect of disease on any individual.

    IVI
    Posted 17-Oct-2011 at 04:15 PM (16:15) by Unregistered
  12. Old Comment
    Gurdur's Avatar

    archaeologist's stories and hard science

    Quote:
    Originally Posted by Unregistered View Comment
    ... The absence of Y.pestis in skeletons from a number of European plague pits dated to the the Black Death years clearly suggests at least one other lethal communicable disease was in play. ......
    IVI
    ^^ This. Many thanks for your comment!
    Posted 17-Oct-2011 at 06:44 PM (18:44) by Gurdur Gurdur is offline
  13. Old Comment
    Yes, staph infection could be passed on by contact but would not, I think, be generally that dangerous unless there was a break in the skin. Something like Ebola fever would result in a higher death rate. Presumably, if not the plague, the disease that caused or contributed to the Black Death had symptoms which looked to some extent similar.

    Savi Hensman
    Posted 17-Oct-2011 at 09:43 PM (21:43) by Unregistered
  14. Old Comment
    Gurdur's Avatar
    Quote:
    Originally Posted by Unregistered View Comment
    Yes, staph infection could be passed on by contact but would not, I think, be generally that dangerous unless there was a break in the skin. Something like Ebola fever would result in a higher death rate. Presumably, if not the plague, the disease that caused or contributed to the Black Death had symptoms which looked to some extent similar.

    Savi Hensman
    Staph can be very dangerous. But under relatively normal circumstances, even given endemic malnutrition and no treatment, staph is most certainly not going to kill off 30% or 50% of your population practically all in in only a couple of goes. Can't be staph. Moreover it's not going to move in waves like the Black Death did. Staph once there hangs around.

    And yes, a few things can look similar to the Black Death, including Ebola-like viral infections, viral hemorrhagic fevers.

    Typhoid, typhus and all the other usual suspects simply don't match how the Black Death happened. Can't be much of a usual suspect.

    Or, in other words, buggered if I know. Real bloody mystery still, innit?
    Posted 18-Oct-2011 at 01:25 PM (13:25) by Gurdur Gurdur is offline
  15. Old Comment
    IMO, your post is a trifle inconsistent, since you seem to imply that Y. pestis has only been confirmed in a few burials during Justinian's plague but not during the Black Death (that's how I read it anyway, sorry if that wasn't your intent), but you quote genetic studies on medieval Y. pestis DNA that was taken from Black Death graves. Also, the results of Bos et al don't imply that "it wasn't around back much before then, in any recognisable form", only that the Black Death form is the ancestor of the modern strains infecting humans. There could have been previous strains that died out. /windy
    Posted 22-Oct-2011 at 08:49 PM (20:49) by Unregistered
  16. Old Comment
    Gurdur's Avatar
    Quote:
    Originally Posted by Unregistered View Comment
    IMO, your post is a trifle inconsistent, since you seem to imply that Y. pestis has only been confirmed in a few burials during Justinian's plague but not during the Black Death
    I imply nothing. I cited some studies, one of which claimed to have found Y. pestis in two victims from around the time of the Justinian plague, and one study, a large one with many subjects from around the time of the Black Death, which claimed to have found no Y. pestis at all.

    Any inconsistancy is in how evidence and interpretations clash, and I already noted they clash in my very first sentences of my post.

    Quote:
    ... but you quote genetic studies on medieval Y. pestis DNA that was taken from Black Death graves. Also, the results of Bos et al don't imply that "it wasn't around back much before then, in any recognisable form", only that the Black Death form is the ancestor of the modern strains infecting humans. There could have been previous strains that died out. /windy
    And I cited one study that claimed to have found through (phylogenetic) analysis that Y. pestis could not have arisen much prior to the Black Death time.

    Except of course as I noted, a different study claims to have found Y. pestis existing well over 500 years or so earlier in victims of the Justinian plague.

    Or, in other words, the studies clash, and the alleged evidence clashes. This is not my interpretation, this is mere noting of the most recent studies to date, and the background.
    Posted 24-Oct-2011 at 04:00 PM (16:00) by Gurdur Gurdur is offline
  17. Old Comment
    "And I cited one study that claimed to have found through (phylogenetic) analysis that Y. pestis could not have arisen much prior to the Black Death time."

    As I explained above, they don't claim that: you have misunderstood the results. /windy
    Posted 24-Oct-2011 at 10:46 PM (22:46) by Unregistered
  18. Old Comment
    Gurdur's Avatar
    Quote:
    Originally Posted by Unregistered View Comment
    "And I cited one study that claimed to have found through (phylogenetic) analysis that Y. pestis could not have arisen much prior to the Black Death time."

    As I explained above, they don't claim that: you have misunderstood the results. /windy
    No. Here is what the study itself said:

    "Genetic architecture and phylogenetic analysis indicate that the ancient organism is ancestral to most extant strains and sits very close to the ancestral node of all Y. pestis commonly associated with human infection. Temporal estimates suggest that the Black Death of 1347–1351 was the main historical event responsible for the introduction and widespread dissemination of the ancestor to all currently circulating Y. pestis strains pathogenic to humans, and further indicates that contemporary Y. pestis epidemics have their origins in the medieval era.
    .....
    Y. pestis is a recently evolved descendent of the soil-dwelling bacillus Yersinia pseudotuberculosis, ....
    ......
    Temporal estimates indicate that all Y. pestis commonly associated with human infection shared a common ancestor sometime between 668 and 729 years ago (ad 1282–1343, 95% highest probability density, HPD), ....
    ......
    This implies that the medieval plague was the main historical event that introduced human populations to the ancestor of all known pathogenic strains of Y. pestis. ..."


    There is their claim in black and white, Windy. Exactly what am I supposed to have misunderstood? As I see it, they're saying Y. pestis in its current infective and epidemic form simply did not exist much prior to the Black Death itself, only an ancestor bacterium existed. Or, in other words, as I said, not in a recognisable form as infective Y. pestis. Why do you think I have misunderstood this?
    Posted 25-Oct-2011 at 11:43 AM (11:43) by Gurdur Gurdur is offline
  19. Old Comment

    rats

    On why the Black Death could not have been rat-borne, I believe the first study (occasionally uneven on the history, but really good on rats, on which the author was an expert) is Graham Twiggs' 1984 "The Black Death: A Biological Reappraisal)." Having read that, I've been following this debate for years: it is good that there is now a debate--the source used to be just assumed.
    Posted 29-Oct-2011 at 06:53 PM (18:53) by Unregistered
  20. Old Comment
    From the same Bos et al study: "our temporal estimates imply that the pandemic [of Justinian] was either caused by a Y. pestis variant that is distinct from all currently circulating strains commonly associated with human infections, or it was another disease altogether." As they correctly point out, they can't exclude the possibility of a separate now-extinct strain of the bacterium being involved in earlier pandemics. /windy
    Posted 01-Nov-2011 at 11:32 PM (23:32) by Unregistered
  21. Old Comment
    Gurdur's Avatar
    Quote:
    Originally Posted by Unregistered View Comment
    From the same Bos et al study: "our temporal estimates imply that the pandemic [of Justinian] was either caused by a Y. pestis variant that is distinct from all currently circulating strains commonly associated with human infections, or it was another disease altogether." As they correctly point out, they can't exclude the possibility of a separate now-extinct strain of the bacterium being involved in earlier pandemics. /windy
    They leave in the thin possibility that IF their research study conclusion is correct, then there was a completely different - very, very different - Y. pestis strain in Justinian's time; but it's a very thin possibility. No descendents, totally extinct, no evidence left behind? Very unlikely. Given Y. pestis does survive today in main strains. I hadn't bothered factoring in that possibility, because it seems such a small one.

    Of course, as I cited, the other study claiming to have found recognisable (and related) Y. pestis in two 6th century skeletons kinda blows Bos et al out of the water. IF true.
    Posted 02-Nov-2011 at 02:00 AM (02:00) by Gurdur Gurdur is offline
    Updated 02-Nov-2011 at 02:20 AM (02:20) by Gurdur
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