Familiar with the Pharaohs. One of the deadliest human diseases is much older than thought
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Researchers have studied ancient DNA and concluded that it is at least 2,000 years older, than expected.
Smallpox left its indelible mark on human history, killing at least 300 people in the 20th century alone. Despite its notoriety, the origin of the smallpox virus is still poorly understood, writes Science Alert.
Back in 2016, thanks to a lucky discovery in Lithuania, scientists traced the smallpox virus back to the 1500s, using viral DNA extracted from the remains of a young boy. In 2020, scientists again made a discovery, pushing back the appearance of smallpox by a few hundred years back, to 1050 AD – this is evidenced by viral DNA from the skeletons of the Viking Age.
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However, historical records hint that something like smallpox struck ancient societies much earlier. Scientists have found descriptions of symptoms very similar to the smallpox virus in texts from 4th-century China. Moreover, pockmark scars on Egyptian mummies suggest that the disease circulated about 2,000 to 4,000 years ago. But for a long time, scientists had only texts, and it was not so easy to find the final genetic evidence, so to speak, the “molecular fingerprint of the virus”.
In a new study, a group of scientists led by bioinformatician Diego Forni from the Institute of Science Research, Hospitalization and Health Care (IRCCS) in Italy examined the genetic sequences of 54 variola virus or VARV samples extracted from previously published papers or taken from a research database.
The scientists studied four ancient VARV genomes from the Viking Age, two historical genomes from the 17th and 18th centuries, and 48 modern sequences obtained before the eradication of smallpox in 1980. Using the available set of viral sequences, scientists reconstructed the evolutionary history of the smallpox virus. As a result, they were able to trace how it branched from one common ancestor into different strains, which eventually either spread around the world or disappeared.
By analyzing the data, the scientists were able to trace the history of smallpox and found that the most recent ancestor of all VARV genomes dates back to about 3,800 years ago, and possibly even earlier. The scientists also compared the sequences of VARV with two other related orthopoxviruses (tatherapox, which infects gerbils and camelpox) – the results of the analysis show that the ancestor of the smallpox virus diverged from its relatives about 7,700 years ago.
Scientists believe that smallpox may have spread to humans between 8,000 and 4,000 years ago – this window is still fairly wide, but it does give an indication that smallpox has actually been around for thousands of years longer than earlier analyzes suggested. DNA samples.
According to Forney, his and colleagues' work proves that the variola virus may be much older than scientists previously thought. In essence, this study is evidence that smallpox actually existed in ancient societies.
At the same time, Forney notes that despite the fact that new dating estimates place smallpox in the correct time frame and now it corresponds to the descriptions of the Egyptian pharaohs.
However, scientists still retain some skepticism about how widespread the smallpox virus was at that time, because scientists have too few ancient documents describing smallpox-like symptoms. To make matters worse, there are a number of other infections that could have caused pharaohs to develop rashes, which means scientists will need to sequence more archaeological specimens to understand which ancient societies were actually affected by smallpox.