[Question] How Old is Smallpox?

The con­ven­tional view is that smal­l­pox has been around since an­tiquity, but more re­cent ev­i­dence has sug­gested it’s ac­tu­ally only around 500 years old.

So I have a re­search/​ra­tio­nal­ity ques­tion: how con­clu­sive is the “500 years old hy­poth­e­sis”? I don’t re­ally have the ex­per­tise to eval­u­ate it.

The wikipe­dia en­try briefly notes the new find­ings, but doesn’t seem to have rewrit­ten the over­all his­tory sec­tion:

The ear­liest cred­ible clini­cal ev­i­dence of smal­l­pox is found in the smal­l­pox-like dis­ease in med­i­cal writ­ings from an­cient In­dia (as early as 1500 BC),[54][55]Egyp­tian mummy of Ram­ses V who died more than 3000 years ago (1145 BC)[56] and China (1122 BC).[57] It has been spec­u­lated that Egyp­tian traders brought smal­l­pox to In­dia dur­ing the 1st mil­len­nium BC, where it re­mained as an en­demic hu­man dis­ease for at least 2000 years. Smal­lpox was prob­a­bly in­tro­duced into China dur­ing the 1st cen­tury AD from the south­west, and in the 6th cen­tury was car­ried from China to Ja­pan.[26] In Ja­pan, the epi­demic of 735–737 is be­lieved to have kil­led as much as one-third of the pop­u­la­tion.[14][58] At least seven re­li­gious deities have been speci­fi­cally ded­i­cated to smal­l­pox, such as the god So­pona in the Yoruba re­li­gion. In In­dia, the Hindu god­dess of smal­l­pox, Si­tala Mata, was wor­shiped in tem­ples through­out the coun­try.[59]
A differ­ent view­point is that smal­l­pox emerged 1588 AD and the ear­lier re­ported cases were in­cor­rectly iden­ti­fied as smal­l­pox.[60][61]

Paper: 17th Cen­tury Var­i­ola Virus Re­veals the Re­cent His­tory of Smallpox

The pa­per ar­gu­ing the 500 years hy­poth­e­sis is here.

High­lights:

• Var­i­ola virus genome was re­con­structed from a 17th cen­tury mum­mified child
• The archival strain is basal to all 20th cen­tury strains, with same gene degradation
• Molec­u­lar-clock analy­ses show that much of var­i­ola virus evolu­tion oc­curred recently

Abstract

Smal­lpox holds a unique po­si­tion in the his­tory of medicine. It was the first dis­ease for which a vac­cine was de­vel­oped and re­mains the only hu­man dis­ease erad­i­cated by vac­ci­na­tion. Although there have been claims of smal­l­pox in Egypt, In­dia, and China dat­ing back mil­len­nia [1, 2, 3, 4], the timescale of emer­gence of the causative agent, var­i­ola virus (VARV), and how it evolved in the con­text of in­creas­ingly wide­spread im­mu­niza­tion, have proven con­tro­ver­sial [4, 5, 6, 7, 8, 9].
In par­tic­u­lar, some molec­u­lar-clock-based stud­ies have sug­gested that key events in VARV evolu­tion only oc­curred dur­ing the last two cen­turies [4, 5, 6] and hence in ap­par­ent con­flict with anec­do­tal his­tor­i­cal re­ports, al­though it is difficult to dis­t­in­guish smal­l­pox from other pus­tu­lar rashes by de­scrip­tion alone.
To ad­dress these is­sues, we cap­tured, se­quenced, and re­con­structed a draft genome of an an­cient strain of VARV, sam­pled from a Lithua­nian child mummy dat­ing be­tween 1643 and 1665 and close to the time of sev­eral doc­u­mented Euro­pean epi­demics [1, 2, 10]. When com­pared to vac­ci­nia virus, this archival strain con­tained the same pat­tern of gene degra­da­tion as 20th cen­tury VARVs, in­di­cat­ing that such loss of gene func­tion had oc­curred be­fore ca. 1650.
Strik­ingly, the mummy se­quence fell basal to all cur­rently se­quenced strains of VARV on phy­lo­ge­netic trees. Molec­u­lar-clock analy­ses re­vealed a strong clock-like struc­ture and that the timescale of smal­l­pox evolu­tion is more re­cent than of­ten sup­posed, with the di­ver­sifi­ca­tion of ma­jor viral lineages only oc­cur­ring within the 18th and 19th cen­turies, con­comi­tant with the de­vel­op­ment of mod­ern vac­ci­na­tion.
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