New York, March 7 (TIWN): When 109-year-old Jessie Gallan was asked about the secret to her long life, she replied “staying away from men.” Other people older than 100 have extolled the virtues of everything from crossword puzzles to tap dancing. One thing they don’t usually mention: chromosomes. Yet, across the animal kingdom, individuals with identical sex chromosomes—including women with double Xs—live nearly 18% longer than their counterparts with mismatched chromosomes, a new study reveals.

In most animals, sex chromosomes help determine whether an individual develops as a male or female. In mammals, females typically have two identical X chromosomes, whereas males have one X and one much smaller, or “reduced,” Y chromosome. Sexes of some animals, such as most male arachnids, lack a second sex chromosome entirely. These chromosomes contribute to the physical differences between males and females. Birds with ZZ sex chromosomes, for example, are male and tend to be more colorful, whereas ZWs are females with typically blander plumage.