Natural selection usually eliminates the most dangerous mutations in our DNA—but one "loophole" ends up being a raw deal for males, LiveScience notes. It involves mitochondrial DNA, which typically comes entirely from the mother. Over time, moms weed out harmful mutations instead of passing them along to offspring. But if a particular mutation happened to be harmful only to males and not females, it might still squeak through. The buildup of such mutations may be why men usually don't live as long as women, scientists speculate.
Scientists implanted different mitochondrial DNA into fruit flies whose cellular DNA was identical. The result: "There was a lot of variation in terms of male longevity and male aging, but almost no variation in the female parameters of aging," a researcher says. The findings pose a problem for guys: "We're not looking for the mutation that causes early male aging, we're actually dealing with a whole lot of mutations ... that are teaming up to shorten male life span." Click through for the full piece. (Read more DNA stories.)