On: Why do women live longer than men?

[makeitdouble]

The genetic explaination I heard was having both full X chromosomes allowed for balance and backup when part of it is corrupted/non functional.

[scarmig → makeitdouble]

I was curious to see how this works in birds, which have the ZW system, where Z is the larger chromosome and which males have two of. And, as it turns out, male birds live longer than female ones.