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Published on: 7/6/2009
Last Visited: 7/6/2009
Peter Ward says life has a history of creating the conditions for its own destruction. (University of Washington)
In Greek mythology, the goddess Gaia emerges from Chaos to, among other things, give rise to all creatures of Earth.
She is Mother Nature: powerful and omnipresent, but nurturing, too, the protector and sustainer of life.
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Among them is Peter Ward, a paleontologist at the University of Washington and NASA astrobiologist who says "the whole idea is nonsensical."
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In "The Medea Hypothesis" (Princeton University Press), Ward asserts that life may be its own worst enemy.
Rather than working to sustain and promote itself, life regularly takes itself out, creating conditions that have resulted in some of the planet's worst mass extinctions.
"Unfortunately, this idea that if we could just get back to nature everything would be fine is not true," said Ward.
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But worse, said Ward, was a subsequent mass extinction 2.3 billion years ago when the Earth endured a period of global glaciation lasting 100 million years.
The cause, says Ward, was again life itself.
Two hundred million years earlier, photosynthesis had debuted, the biological process by which atmospheric carbon dioxide and sunlight are converted into usable energy, with oxygen generated as a waste product.
Before photosynthesis, atmospheric levels of oxygen were relatively low.
The gas was poisonous to early life.
But with the emergence of photosynthesis, microbes began sucking so much heat-trapping carbon dioxide out of the atmosphere that the planet froze, said Ward.
Virtually everything died, except for the photosynthesizers and microbes that quickly adapted to tolerate higher oxygen levels.
Ward says the rise of multicellular plants produced a similar cataclysmic decline in atmospheric CO2 and a second "snowball Earth" 700 million years ago.
And he contends there is strong evidence most of the mass extinctions since the evolution of animals 565 million years ago have been, in some way, driven by adverse microbial activity.
These biologically induced mass extinctions are quite contrary to the idyllic concepts of Gaia, says Ward.
And while life on Earth has enjoyed long periods of stability, Ward adds that it also has a nasty streak of self-destructiveness that is bound to rise again.
Next time, he said, will be the last time.
The end begins with the sun, according to Ward, which has increased in brightness by about 30 percent over the past 4.5 billion years.
That trend will continue, spurring global warming which will, in turn, boost the weathering rate of silicate rocks like granite, a process that chemically removes CO2 from the atmosphere.
At first, Ward speculates, the atmospheric loss of CO2 will benefit life by buffering the rising temperatures caused by a hotter sun.
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Ward also expects humanity to suffer in the shorter term, largely from problems of its own making.
"There are too many people on the planet.
We're consuming resources too rapidly.
We're exacerbating climate change.
In the short term, we will have some horrible things to deal with."
Nonetheless, Ward considers his hypothesis to be the more optimistic of the two.
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Ward said there's "no going back to nature."
"Nobody wants to return to sitting around campfires with no clothes.
The challenge is finding the least amount of technology that we, as a species, are willing to live with that's harmonious with keeping alive as many other species as possible."
Ward believes - or at least strongly hopes - that human society will somehow muddle through the next few centuries, that it will find ways to minimize and adapt to predicted or unexpected environmental catastrophes like climate change, rising sea levels and mass extinction.
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