Whether it’s famine, war or epidemics: women around the world are older than men. Also many animal species that is so, but why? Scientists at the University of San Francisco think that it is the chromosome on the X -.

The X chromosome not only determines gender, it has many genes that are necessary for Survival. Women have two, men only one. Men have a Y chromosome, however, except for the genes for the male sex, and the facial hair is hardly anything.

On the basis of animal experiments with mice, the sex chromosomes have been artificially altered, the researchers found that only female mice with two X-chromosomes reached the maximum life span of about 30 instead of an average of 21 months.

The chromosomes of the mice were so altered that, in addition to normal females with two X chromosomes and the male XY animals mice with female genitals and XY equipment, as well as mouse organs, with the male gender, and two X-chromosomes were grown. Under the same conditions was observed, how long the animals lived. The XX animals with male sex organs, for instance, Enjoyed 23 months of age and, therefore, also slightly older than their male XY. The longest normal female mice lived with two X-chromosomes.