Over the course of the human life span, somatic DNA mutations accumulate in healthy
tissues. This process has been most clearly described in blood and bone marrow,
esophagus, colon, and skin, but cumulative DNA damage likely affects all tissues of the
body. Although most acquired genetic variants have no discernable functional
consequences, some randomly occurring somatic mutations confer a relative fitness
advantage on a single stem cell and its progeny compared with surrounding cells, which …