Say NO to O2 but don't hold your breath

Millions of years ago, the Earth did not have much in the way of oxygen. Microbes lived happily in the methane environment...and I am told (sorry can't recall the reference, probably Horizon BBC) that they were 'eternal'. Only physical misfortunes such as being melted in a volcanic eruption killed them off. Then along came OXYGEN and life became mortal: In medieval times, air was thought to be spirit.....

....you start with your first breath and go out with your last gasp.

In other words OXYGEN is a killer.

You too can be eternal, just don't oxidise yourself. This does of course mean stopping breathing and I feel may be very very difficult to manage for most.