This is a story about trees—very, very strange looking trees—and some microbes that failed to show up on time. Their non-appearance happened more than 300 million years ago, and what they didn’t do, or rather what happened because they weren’t there, shapes your life and mine.

All you have to do is walk the streets of Beijing or New Delhi or Mexico City: If there’s a smog-laden sky (and there usually is), all that dust blotting out the sun is there because of this story I’m going to tell (See the effect of burning coal in one of the world's most polluted cities).

It begins, appropriately enough, in an ancient forest …

… whose trees “would appear fantastic to us in their