The Medea Hypothesis: Earth's appetite for destruction  

The Boston Globe has an article about paleontologist Peter Ward's anti-Gaia hypothesis, called the Medea hypothesis - Dark green. Ward will have his TED Talk from last year up on the web shortly.

WHEN WE LOOK at nature, it has become commonplace to see a fastidiously self-regulating system at work: wildebeest trim the savannah grasses, lions cull the wildebeest herds, and vultures clean the bones of both. Forests take in the carbon dioxide we exhale, use it to grow, and replace it with oxygen. The planet even has a thermostat, the carbon cycle, which relies on the interplay of volcanoes, rain, sunlight, plants, and plankton to keep the earth's temperature in a range congenial to life.

This idea of nature's harmonious balance has become not just the bedrock of environmental thought, but a driving force in policy and culture. It is the sentiment behind Henry David Thoreau's dictum, "In wildness is the preservation of the world." It lies behind last summer's animated blockbuster "Wall-E," in which a single surviving plant helps revive an earth smothered beneath the detritus of human overconsumption. It underlies environmental laws that try to minimize the damaging influence of humans on land and the atmosphere.

In this line of thought, the workings of the natural world, honed over billions of years of evolution, have reached a dynamic equilibrium far more elegant - and ultimately durable - than the clumsy attempts humankind makes to alter or improve them.

According to the paleontologist Peter Ward, however, nothing could be further from the truth. In his view, the earth's history makes clear that, left to run its course, life isn't naturally nourishing - it's poisonous. Rather than a supple system of checks and balances, he argues, the natural world is a doomsday device careening from one cataclysm to another. Long before humans came onto the scene, primitive life forms were busily trashing the planet, and on multiple occasions, Ward argues, they came close to rendering it lifeless. Around 3.7 billion years ago, they created a planet-girdling methane smog that threatened to extinguish every living thing; a little over a billion years later they pumped the atmosphere full of poison gas. (That gas, ironically, was oxygen, which later life forms adapted to use as fuel.)

The story of life on earth, in Ward's reckoning, is a long series of suicide attempts. Four of the five major mass extinctions since the rise of animals, Ward says, were caused not by meteor impacts or volcanic eruptions, but by bacteria, and twice, he argues, the planet was transformed into a nearly total ball of ice thanks to the voracious appetites of plants. In other words, it's not just human beings, with our chemical spills, nuclear arsenals, and tailpipe emissions, who are a menace. The main threat to life is life itself.

"Life is toxic," Ward says. "It's life that's causing all the damn problems."

Ward, a paleontologist at the University of Washington and a scholar of the earth's great extinctions, calls his model the Medea Hypothesis, after the mythological Greek sorceress who killed her own children. The name makes clear Ward's ambition: To challenge and eventually replace the Gaia Hypothesis, the well-known 1970s scientific model that posits that every living thing on earth is part of a gargantuan, self-regulating super-organism.