No announcement yet.

DNA and the Black Death

  • Filter
  • Time
  • Show
Clear All
new posts

  • DNA and the Black Death

    Here's an interesting article which raises the topic of how diseases influenced the kind of DNA geographical patterns we see today:

    The English are less genetically diverse than in the past – and plague in the Middle Ages is the most likely cause

    Black Death casts a genetic shadow over England
    12:26 01 August 2007 news service
    Colin Barras

    The Black Death
    Susan Scott's homepage (with links to a list of publications):
    The Black Death continues to cast a shadow across England. Although the modern English population is more cosmopolitan than ever, the plagues known as the Black Death killed so many people in the Middle Ages that, to this day, genetic diversity is lower in England than it was in the 11th century, according to a new analysis.

    Rus Hoelzel at the University of Durham, UK and his colleagues looked at the mitochondrial DNA from human remains at 4th and 11th century archaeological sites in England, and compared them to samples from the modern population stored on DNA databases such as GenBank. They found there was more variation in the ancient mitochondrial DNA sequences than in modern sequences.

    Hoelzel thinks random genetic drift may have lowered genetic diversity naturally. But the large unexpected drop in diversity was more likely to have been caused by population crashes following major outbreaks of the Black Death in England during the 1340s and the 1660s.

    "The main factors in support of a role for plague are the timing and the fact that it affected different families [to a differing degree]," says Hoelzel.

    Vulnerable families
    The Black Death did not reach England until the mid-14th century. No-one knows exactly what caused it, with the bubonic plague bacterium Yersinia pestis, and various viruses all having been implicated at some point.

    However, it is known that plague affected some families more than others, so their mitochondrial DNA would have been less common among survivors, Hoelzel says.

    "I'm not at all surprised with the result," says Susan Scott at the University of Liverpool, UK. "We're talking about one of the worst disasters humans have faced. It destroyed about half the population of Medieval Europe in three years."

    But the effects may have been most severe in northern Europe. Hoelzel and his team note that DNA sequences from modern Italians are just as variable as those from their 7th century ancestors.

    According to Hoelzel, this finding may reflect migration patterns after the Black Death, rather than a less severe outbreak in southern Europe. "Throughout the recent past, there have been movements from the Middle East into southern Europe, and the Middle East population retains a great mix and diversity," he says.

    Effective measures
    Scott has a different theory. "We have to listen to the people who were suffering at the time," she says. "The disease came in from Sicily and seemed to settle in France where it was endemic for almost 200 years."

    France was probably the source of the periodic epidemics elsewhere in Europe, and these were infrequent in Italy because of the vigilant actions of the Italian authorities, Scott thinks.

    "They closed down ports and stopped people travelling at the first sign of infection," she says. "And they had a 40-day quarantine period. I think the Black Death was the result of a virus that probably had a 37-day incubation and infection period, so the Italian quarantine period was just right."

    "In England, King Henry VIII reduced [the quarantine period] to 30 days at one point, and the country suffered," says Scott.

  • #2
    That King Henry VIII was a total jerk. Not only does he kill a few of his wives he reduced the quarantine that led to greater suffering of his people.


    • #3
      delta 32

      delta 32 is a mutation which if someone had two copies they didnt get the plague at all
      one copy they got mildly sick
      secret of the dead pbs did a show on the geneaoly research of a british town

      turns out delta does the same thing for aids


      • #4
        Originally posted by Jim Denning
        delta 32 is a mutation which if someone had two copies they didnt get the plague at all
        one copy they got mildly sick
        secret of the dead pbs did a show on the geneaoly research of a british town

        turns out delta does the same thing for aids
        I saw that show. I assume the undertaker had two copies of delta 32, because he didn't get sick. I also remember the re-enactment of the sick girl coming to and chugging down bacon fat that she thought was something else. Afterwards people thought it was the bacon fat that cured her. One has to be very, very sick to drink bacon fat and not notice how it tastes.

        I ordered the test and it's in batch 213. Due around August 27th. I hope I have two copies.

        Side note: I wish DNATRIBES would include that town in it's populations.


        • #5
          If the plague wiped-out half the breeding population of Medieval Europe and 'nature abhors a vacuum' perhaps those are the reasons for the present day ubiquity of mt-H and y-R1b1c?


          • #6
            I found a link to the study for those of you who just love to wade through the numbers and charts.