Oxygen

Life has been changing the environment almost from the minute it got started. In Origin Story, David Christian points out that almost 3 billion years back, cyanobacteria evolved photosynthesis:

H2O + CO2 + energy from the sun = Carbohydrates + O2

As a result, carbon dioxide levels started falling in the atmosphere. But the oxygen levels did not start rising, at least not for some time. Why not?

 

As this BBC podcast says, the reason is obvious once you hear it: oxygen is among the most reactive elements in the universe. Ergo, the released oxygen reacted with pretty much everything out there and never stayed “free” in the atmosphere.

 

But eventually, all the oxygen “sinks” were full. And then the oxygen levels in the atmosphere began to rise massively and rapidly, all the way from practically non-existent levels to 35% (Current levels are 21%). This spike in oxygen levels was lethal to most life forms back then for a reason that’ll sound very weird to us from the 21% levels of today: oxygen was poison to them! So much so that the rise in oxygen levels led a to a mass extinction event back then.

 

Life evolved to live with the oxygen levels, even learning to use it to produce energy via the technique called respiration. Or as Christian describes it:

“Life’s delicate, nondisruptive equivalent of fire.”

But even now, the podcast points out, handling oxygen within the body is like playing with fire. Life forms today still handle oxygen with extreme caution, with catalysts that act as tweezers to pick up and transfer oxygen molecules to the safe parts of the cell. And to handle the odd oxygen molecules that go rogue within the body? The body has anti-oxidants for just that scenario.

 

The uber-reactiveness of oxygen is known to us most commonly by the problems of fire and rusting. As the podcast says, a huge amount of money is spent world over to prevent and undo the effects of rusting. Which is why the interest in the Iron Pillar in Delhi never goes away: it hasn’t rusted in over 1,600 years. What’s the secret? Nobody knows, but it isn’t for want of trying. If the answer is found out, it will almost certainly create a multi-billion dollar industry against the problem of rusting.

 

Oxygen: can’t live without it, and yet it is also a danger (and problem).

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