It has long been known that genetic material is mutable at a rate subject to natural selection, but multicellular organisms have a somatic genome with a mutation rate that differs from the germline mutation rate. However, a lack of reliable methods to measure somatic mutation frequencies in DNA have precluded a direct comparison in mutation rates between somatic and germline cells. Vijg and colleagues present the first direct comparison of mutation rates in human and mouse single somatic cells, both of which are further compared to human and mouse de novo germline mutation rates. The CellRaft® Technology is utilized here to isolate single cells for downstream single cell whole genome sequencing after amplification. The results presented suggest that somatic mutation frequencies are significantly higher than germline mutation frequencies, which may point toward somatic mutations as a conserved mechanism of aging.