Why do females usually live longer than males? Science may have the answer, dubbed the "Mother's Curse" hypothesis:
The loophole lies in the mitochondria, the energy-generating parts of our cells. The mitochondria have their own DNA, separate from the DNA that resides in the nucleus of the cell that we usually think of when we think of the genome. In almost all species, the mitochondria DNA is passed down solely from mother to child, without input from dad.
This direct line of inheritance may allow harmful mutations to accumulate, according to a new study detailed today (Aug. 2) in the journal Current Biology. Ordinarily, natural selection helps keep harmful mutations to a minimum by ensuring they're not passed down to offspring. But if a mitochondrial DNA mutation is dangerous only to males and doesn't harm females, there's nothing to stop mom from passing it to her daughters and sons.
"If a mitochondrial mutation pops up that is benign in females, or a mutation pops up that is beneficial to females, this mutation will slip through the gates of natural selection and go through to the next generation," said study researcher Damian Dowling, an evolutionary biologist at Monash Univeristy in Australia.
The result: a load of mutations that don't harm females, but add up to a shorter life span for males.