2.5 Billion Years Ago

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Gas attack

Flooding the atmosphere with toxic fumes is one way to wipe out your

competitors

By Gretel H. Schueller

WARRIOR RACE? Forget it. When it comes to poisoning the planet and

butchering neighbours, humans can't hold a candle to our one-celled

ancestors. Some 2.5 billion years ago, bacteria waged chemical warfare on

their fellow beings, wiped out most of them and transformed the Earth. You

and I are still living off the proceeds: without that act of unparalleled

genocide, none of us--and nothing like us--would exist.

On the eve of destruction, 3 billion years ago, Earth was a raging party. As

volcanoes spewed out sulphurous gases and carbon dioxide, the world's waters

teemed with brilliantly coloured single-celled creatures living it up. Some

freeloaded, sopping up amino acids and other biochemicals forged in the

atmosphere by ultraviolet rays and lightning. Others devised chemical

processes, such as fermentation, to break down molecules--mostly

nitrogen--and release their stored energy. Still others harnessed sunlight

to whip up energy-rich glucose from the sulphur and carbon dioxide that

eventually washed into the seas. As Earth's only inhabitants, these

microorganisms ruled the roost, feasting, multiplying, covering the globe

with a patina of life.

Then things started to turn sour. As populations boomed, food, inevitably,

became scarce. Pressure to survive intensified. Around 2.6 billion years

ago, a new gang of microbial toughs broke up the orgy...

The full article is available in the 7 August issue of New Scientist

magazine. See below for details.

Read the full Disaster Supplement in the 7 August 1999 print edition of New

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From New Scientist, 7 August 1999