Mystery of lifespan gap between sexes may be solved, say researchers

Study finds chromosomes offer clue to longer life of different sexes in different species

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.