The Historical Roots of Smallpox and Other Viruses: A Deep Dive into Their Early Appearances
Smallpox's Hidden History Unveiled by New Genetic Research
Smallpox, the deadly virus responsible for killing millions, has finally yielded some of its secrets with fresh insights from genetic analysis. A recent study by British science journalist and author Laura Spinney reveals that smallpox's origins are becoming increasingly clear, pushing its history back by a millennium.
Dating back to AD 600, humans carried the variola virus, an international team of researchers reported this week. Furthermore, their study suggests that the virus was already spreading among people at least 1,700 years ago, during the tumultuous period preceding the fall of the Western Roman Empire.
Smallpox is not the first infectious disease to see its history drastically revised in the past decade due to ancient-DNA analysis. Earlier this year, a study proposed that measles, believed to have started affecting humans around the ninth century, may have made the jump to humans as early as the first millennium BCE. This is when its genetic sequence appears to have diverged from that of the rinderpest virus, another disease that infected cattle and was eradicated in the late 20th century.
These findings offer a new perspective on how diseases shaped human populations throughout history. Ann Carmichael, a plague historian at Indiana University in Bloomington, comments that genetic evidence points to a connection between diseases such as plague and hepatitis B and significant prehistoric migrations. It remains unknown whether these migrations were caused by the emergence of disease or whether the emergence of disease was triggered by migrations. Archaeologists, historians, and geneticists hope to answer this question soon.
One of the most significant advancements in uncovering disease histories is the development of new methods for reconstructing entire genomes of ancient pathogens. In 2011, scientists published the first such genome, that of Yersinia pestis, gathered from four skeletons in a London graveyard dating back to the Black Death.
In the current study, researchers screened DNA collected from 1,867 individuals who lived between 32,000 and 150 years ago across Eurasia and the Americas. They found traces of the variola virus in 26 individuals, such as a mass grave from Oxford, UK, dating back to the St Brice's Day Massacre of 1002. Four Viking-era individuals provided enough viral DNA for researchers to reconstruct near-complete variola genomes.
Unexpectedly, the lineage detected in these samples was not a direct ancestor of the modern-day lineage. Instead, it constitutes a separate evolutionary trajectory that didn't carry over to the modern day variola. Researchers traced this family tree using molecular clock analysis, estimating a most recent common ancestor lived around 1,700 years ago.
Despite this advancement, much still remains unknown about smallpox and its origins. Some historical records suggest that smallpox has been afflicting humanity for over 3,000 years, dating back to the time of Pharaoh Rameses V. However, the current study offers no insight into this idea since it didn't find any variola DNA in ancient Egyptian remains.
The debate over the origin and history of smallpox is not over, but new findings allow scientists to address fresh questions and rewrite certain parts of history. Understanding the history of diseases like smallpox can help us better protect ourselves from them in the future.
Smallpox's history, revised in the past decade due to ancient-DNA analysis, shows that the variola virus could have been present as early as AD 600, according to a recent study on medical-conditions like smallpox and chronic-diseases. This research suggests that genetic evidence from health-and-wellness perspectives may reveal connections between diseases and significant prehistoric migrations, which could offer new insights into the shaping of human populations throughout history.
