The pertinent part regards the article you're trying to find/remember is this:
"Remarkably, more recent variants of the bacterium hardly vary compared to the original microbe, says the paper.
"Based on the reconstructed genome, we can say that the medieval plague is close to the root of all modern human pathogenic plague strains," said Krause.
"The ancient plague strain does not carry a single position that cannot be found in the same state in modern strains."
This deep similarity between ancient and modern plague calls into question the long-held assumption that virulence-enhancing mutations are what made Y. pestis so deadly to the Middle Ages."
Basically, the current working theory is based around a susceptible and naive 'terrain' more than a particularly virulent early pathogen. Earlier theories were linked to virulence of Yersinia pestis it appears.
Re: Population Immunity
A quick search unearthed this article from SBS News Australia in 2011:
https://www.sbs.com.au/news/article/why-the-black-death-was-so-lethal/4d27hb9bj
The pertinent part regards the article you're trying to find/remember is this:
"Remarkably, more recent variants of the bacterium hardly vary compared to the original microbe, says the paper.
"Based on the reconstructed genome, we can say that the medieval plague is close to the root of all modern human pathogenic plague strains," said Krause.
"The ancient plague strain does not carry a single position that cannot be found in the same state in modern strains."
This deep similarity between ancient and modern plague calls into question the long-held assumption that virulence-enhancing mutations are what made Y. pestis so deadly to the Middle Ages."
Basically, the current working theory is based around a susceptible and naive 'terrain' more than a particularly virulent early pathogen. Earlier theories were linked to virulence of Yersinia pestis it appears.
This article has more on the sample collection and genetic reconstruction behind the change of emphasis: https://www.scientificamerican.com/article/black-death-genome/