Via FuturePundit, news of a study on telomere differences by gender: "This new study [shows] significantly shorter telomeres and higher erosion rates in men than in women, which likely causes a shorter life expectancy of male cells and tissues. Human telomeres form the terminal structures of human chromosomes and play a pivotal role in the maintenance of genomic integrity and function. During aging, telomeres gradually shorten, eventually leading to cellular senescence." The telomere theory of aging is on the way out, however, and there is some uncertainty as to just what short telomeres mean for health and longevity for any given individual. Like so many things in human biochemistry, it's a very complex question asked about a very complex system.