The geneticists were able to remove and analyze mitochondrial DNA—genetic information extracted from the energy-producing structures within cells—from both infants. Because this genetic material is inherited only from the mother, it gives scientists a way to trace maternal lineage. The scientists found that the two infants did not have the same mother, or even the same maternal grandmother. In fact, the babies came from two separate genetic lineages. According to the study’s authors, both lineages are distinctly Native American, not found in Asia, and both are “rare to absent” from modern northern populations.