Maximum life span (MLS) and abundance of mitochondrial DNA (mtDNA) insertions in the nuclear DNA (NUMTs) were analyzed in 17 animal species with completely sequenced mitochondrial and nuclear genomes. Highly significant positive correlations were found between MLS and NUMT number, total size, or density (both in mammals and all animal species). In mammals, NUMT abundance correlated positively with the mtDNA guanine content and negatively with adenine and thymine contents, but did not correlate with such longevity-associated variables as the body mass and resting metabolic rate.