They also found an unexpectedly high number of these jumping genes, known as transposons, in lung tumors and said they may hold clues to the highly deadly cancer.

“We found that if you have a child, the child could have one or more new copies of these transposons that you don’t have,” Scott Devine of the University of Maryland School of Medicine said in a statement.

“From these findings, we predict that there is going to be more variation in human genomes than scientists first believed,” added Devine, who led the research while at Emory University in Atlanta.