Peter Ward spoke at TED2008 about Earth’s mass extinctions (watch for his TEDTalk later this month). You probably know about one of these events, the Cretaceous-Tertiary extinction 65 million years ago that ended the age of dinosaurs. In today’s Boston Globe, Ward talks with writer Drake Bennett about the other four extinctions — and about the way our planet seems to careen toward destruction over and over.

Ward’s Medea Hypothesis runs counter to the idea that our planet is a self-balancing system; he suggests that, when given the opportunity, any kind of life on Earth, from plants to bacteria to humanity, will run amok and tip the balance toward chaos. From the story:

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.

For more details — and a lively conversation on the Globe site — read the story, Dark Green: A scientist argues that the natural world isn’t benevolent and sustaining: it’s bent on self-destruction >>

And contrast this with Jared Diamond’s 2005 TEDTalk on collapse — as one Globe commenter notes: “human beings … are destructive to the stability of the ecosystems in many cases.”