From humans to black-tailed prairie dogs, female mammals often outlive males – but for birds, the reverse is true.
Now researchers say they have cracked the mystery, revealing that having two copies of the same sex chromosome is associated with having a longer lifespan, suggesting the second copy offers a protective effect.
X,X and X,Y are fairly normal among humans. X,X,Y, and X,Y,Y happen and so on. X,O does too – but O,Y never does.
Further, it’s long been assumed – ‘cuz even I’ve read about it – that if there’s some buggery on one X then the other can take over and correct it, something that can’t happen with the Y, for the same reason that O,Y can’t happen. And I’m alo why no one even speculates about the possible existence of Y,Y.