Men who make it to adulthood without succumbing to the male habit of dying in accidents shouldn’t congratulate themselves too soon: their life expectancy still doesn’t match a woman’s. In industrialized countries, women at every age out-survive men. And it’s not just humans. Males that die before females have been observed throughout the animal kingdom. It’s even true of the lowly fruit fly, and it looks like harmful mutations in mothers’ genes are to blame.
This idea, which has been put forward before, is called the Mother’s Curse. It has to do with a little loop of DNA that’s passed down in humans—and in most other animals—exclusively through the mother. This DNA hides inside the mitochondria, which are the cell’s batteries, and doesn’t get packaged up with the rest of the genetic material when sperm are made. Those tiny sperm will rendezvous (if they’re lucky, of course) with an egg that supplies all its own mitochondria, along with their DNA.
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