Hormesis was first shown to extend life more than a century ago when low doses of radiation

were shown to increase the lifespan of a type of beetle.

Scientists were hoping irradiation with x-rays could kill off the eggs of the grain pest,

but to their surprise, at low doses, it actually made the Beatles live longer.

This was subsequently replicated with gamma rays and about a dozen other insects,

from houseflies and crickets to wasps and mosquitoes, a strongly consistent 20 to 60 percent increase in lifespan.

What is going on?

Hormesis is thought to be an adaptive response

to anticipated potential threats.

The body is able to leverage the initial insult

to prompt a compensatory counter-response

that more than covers the cost of the original

damage and yields a net benefit in the end.

In the case of radiation at high enough doses, it kills by damaging DNA.

Animals have a whole DNA repair apparatus, but it's presumably too metabolically costly

to have it run at full tilt all the time,

even when we don't really need it.

But ramping up DNA insults with low-dose radiation signals to the animal

that they're in a DNA-destructive environment,

so their body starts ramping up DNA repair to compensate.

And a happy side effect of all that extra DNA protection is a longer life.

That which didn't kill them made them stronger.

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