March 7 (UPI) -- Scientists found genetic traces of early leukemia ancestors in the genomes of bats. The discovery, detailed in the journal PNAS, fills the "last major gap" in the retrovirus lineage.
According to the new genomic analysis, deltaretroviruses, a family of viruses responsible for a rare type of leukemia, first evolved between 20 and 45 million years ago. The findings confirm the family's ancient animal origins.
"The discovery of this viral sequence fills the last major gap in the fossil record of retroviruses," Robert Gifford, virus researcher at the University of Glasgow, said in a news release. "It provides a means of calibrating the timeline of interaction between deltaretroviruses and their hosts."
The DNA of the ancient deltaretrovirus was found mixed into a sequence of related Minopterid viral species incorporated in the genome of bent-winged bats between 20 and 45 million years ago. Tracing the evolutionary origins of ancient viruses helps scientists learn about the development the mammalian immune system.
"Understanding the history of these viruses will help scientists to better understand how they affect people and animals now and in the future," Gifford said.
In recent years, scientists have illuminated the evolutionary arms race between viruses and mammalian defenses by locating the genetic remnants of ancient virus species in animal genomes.