Together, the two data sets finally pin down where the species falls on the rodent family tree, the authors of the new study say.
Working independently on separate genetic tests, three research teams in France, Israel, and the United States compared rock rat genes with the counterpart genes in other rodents.
The scientists looked to see if the rock rat shared genetic mutations with other rodent species, which would suggest a close evolutionary relationship.
Also for the new study, German researchers examined other pieces of DNA known as transposons, or "jumping genes."
The genes—which copy themselves, float to other spots in the genome, and randomly insert themselves—told the same story about the rock rat's ancient lineage.
"Their result looks pretty solid," said Ronald DeBry, a molecular biologist at the University of Cincinnati in Ohio who was not involved in the research.
He added that by studying the rodent's jumping genes, the study authors "provide a really important and very convincing independent confirmation" of how the various rodent species are related.
Researchers behind the new study argue that, given the rock rat's unusual lineage, it is important to protect the species.
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