Chromosome Chronology

The Friday File: While the lifespan of women living in, for example, the US averages 81.1 years vs. 76.1 for men, why is debated. A new theory suggests sex chromosomes. Across mammals, birds, reptiles, amphibians, sharks, bony fish, arachnids, and insects, the heterogametic sex (the one having an X and a Y chromosome) has a shorter life! Heterogametic male species average a 20.9% shorter lifespan, heterogametic female species 7.1% shorter.