But to clarify, I don’t think the Antonine plague is quite the same as modern ones, for the simple reason that it could only spread over a fairly limited geographic region, and it could not become endemic because of population density constraints. Smallpox evolution is driven by selection pressure in humans, and the “500 years old” claim is about that evolution, not about whether it affected humans at any time in the past. That said, it absolutely matters, because if the original source of smallpox was only 500 years ago, where did it come from?
The question is how smallpox evolved, and what variant was present prior to the 1500s. It’s plausible that Horsepox, which was probably the source for the vaccine strain, or Cowpox, spread via intermediate infections in cats, were the source—but these are phylogenetically distant enough that, from my limited understanding, it’s clearly implausible that it first infected humans and turned into modern smallpox at recently as the 1500s. (But perhaps this is exactly the claim of the paper. I’m unclear.) Instead, my understanding is that there must have been some other conduit, and it seems very likely that it’s related to a historically much earlier human pox virus—thousands of years, not hundreds.
Yes.
But to clarify, I don’t think the Antonine plague is quite the same as modern ones, for the simple reason that it could only spread over a fairly limited geographic region, and it could not become endemic because of population density constraints. Smallpox evolution is driven by selection pressure in humans, and the “500 years old” claim is about that evolution, not about whether it affected humans at any time in the past. That said, it absolutely matters, because if the original source of smallpox was only 500 years ago, where did it come from?
The question is how smallpox evolved, and what variant was present prior to the 1500s. It’s plausible that Horsepox, which was probably the source for the vaccine strain, or Cowpox, spread via intermediate infections in cats, were the source—but these are phylogenetically distant enough that, from my limited understanding, it’s clearly implausible that it first infected humans and turned into modern smallpox at recently as the 1500s. (But perhaps this is exactly the claim of the paper. I’m unclear.) Instead, my understanding is that there must have been some other conduit, and it seems very likely that it’s related to a historically much earlier human pox virus—thousands of years, not hundreds.