Scientist may have figured out why women live longer than men

In the search for the fountain of youth, “X” marks the spot!

Scientists may have figured out why women live longer than men — linking it to having two X chromosomes, which defend against aging, according to a new study.

The extra X provides a sturdy cellular structure that protects against gene mutation and sickness, according to a report published Wednesday in the journal Biology Letters.

“These findings are a crucial step in uncovering the underlying mechanisms affecting longevity, which could point to pathways for extending life,” the researchers say in the report.  “We can only hope that more answers are found in our lifetime.”

For the study, scientists from the University of New South Wales gathered data on the sex chromosomes and lifespan of 229 species, including insects, fish and mammals.

They found that animals with two of the same sex chromosomes —  such as birds with two “Z” chromosomes —  live nearly 18 percent longer.

Their research piggybacks on a pre-existing theory known as the “unguarded X hypothesis,” which notes that one X serves as a buffer against disease.

As the theory goes,  only one X is activated in each of a woman’s cells, so a harmful mutation in one cell is less likely to effect all cells. That makes mutation-related disorders  “masked” more often in females, according to scientists.

By contrast, guys are more likely to be exposed to the same types of mutations because their XY chromosomes only have a single X.

But there may be other factors tied to why females tend to live longer than males, such as fighting and risk-taking, the scientists said.

“Pressures to travel far to find a mate, establish a territory and compete with other members of your sex are not seen often in females,” said Zoe Xirocostas, who co-authored the report.

“Our study suggests that the unguarded X is an underlying genetic factor that can influence lifespan, but many external factors can influence longevity in different ways such as predation, risky behaviors, establishing territories and access to quality nutrition.”

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