Despite its prevalence, little is known about the ancestral roots of the [hepatitis B] virus. New findings, published [May 9] in Nature, reveal some of the oldest samples of the virus to date—between 800 and 4,500 years old—and provide fresh insights into its origin and evolution.
To probe for signs of ancient outbreaks in individuals who occupied Eurasia from the Bronze Age to the medieval period, the researchers examined DNA extracted from the remains of 304 ancient humans.
…[T]he team found that 25 individuals showed signs of a hepatitis B infection, and that of those, only 12 of the viral genomes, which were between 800 and 4,500 years old, were intact enough for further analysis.
…[M]ost of them could fit into a modern-day genotype, or category based on similarities in their DNA. Three of the genetic sequences, however, did not have a modern match and were linked to at least one newly uncovered strain that is now extinct.
Evolutionary theory predicts that some viral sequences will be lost by random chance, and finding an extinct strain of hepatitis B suggests that the diversity of the virus may have been much greater in the past than it is today.
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