The effect of somatic movement of the mariner transposable element on lifespan was measured in Drosophila simulans and Drosophila melanogaster males at 25 degrees C. In D. simulans this movement significantly decreased lifespan, whereas in D. melanogaster no correlation between transposon movement and lifespan was found. The results in D. simulans support the hypothesis that somatic genetic damage induced by DNA element movement can reduce lifespan.