A Short History of Nearly Everything

However, as Kolbert has pointed out when you are confronted with a fluctuating and unpredictable climate "the last thing you'd want to do is conduct a vast unsupervised experiment on it." It has even been suggested, with more plausibility than would at first seem evident, that an ice age might actually be induced by a rise in temperature. The idea is that a slight warming would enhancec evaporation rates and increase cloud cover, leading in the higher latitudes to more persistent accumulations of snow. In fact, global warming could plausibly, if paradoxically, lead to powerful localized cooling in North America and northern Europe.

I asked RIchard Fortey how science ensures that when one person goes there's someone ready to take his place. He chuckled rather heartily at my naivete. "I'm afraid it's not as if we have substitutes sitting on the bench somewhere waiting to be called in to play. When a specialist retires or, even more unfortunately, dies, that can bring a stop to things in that field, sometimes for a very long while." "And I suppose that's why you value someone who spends forty-two years studying a single species of plant, even if id doesn't produce anything terribly new?" "Precisely," he said, "precisely." And he really seemed to mean it.

We are so used to the notion of our own inevitability as life's dominant species that it is hard to grasp that we are here only because of timely extraterrestrial bangs and other random flukes. The one thing we have in common with all other living things is that for nearly four billion years our ancestors have managed to slip through a series of closing doors every time we needed them to. Stephen Jay Gould expressed it succinctly in a well-known line: "Humans are here today because our particular line never fracured - never once at any of the billion points that could have erased us from history."

"The history of life", wrote Gould, "is a story of massive removal followed by differentiation within a few surviving stocks, not the conventional tale of steadily increasing excellence, complexity, and diversity." Evolutionary sucess, it appeared, was a lottery.