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30 august 2012
Jan Zalasiewicz's intricate and fascinating Earth after Us finally gets around to answering its subtitle question "what legacy will humans leave in the rocks?" but only after thorough grounding of an almost primer-like nature on the geology, paleontology, and the specifics of planetary history that will make such long-term traces perceptible 100 million years from now. And the book is all the better for being largely preamble.
Just to deal first with a personal, readerly fixation of mine: I find The Earth after Us to be exemplary as expository writing. At no point does the author jaunt off via bush plane or Land Rover to gaze on fossiliferous strata. At no point does he interview quirky taphonomists, or have a lunch date with a fetching stratigrapher. He (with the help of Kim Freedman) simply presents narratives and arguments – occasionally enlivening them with personal notes that the reader can relate to, but never forgetting that his book is about rocks and potential rocks, not about amusing travel anecdotes or funny personalities.
And fittingly. The subject matter is what extraterrestrial paleontologists will make of an eons-vanished humanity. At that distance, all our endearing individual qualities are likely to be reduced to a few handfuls of petrified stuff. And most of it will be stuff, not we ourselves. In a sense, our stuff is a lot more interesting than we are. Mammals are pretty common in fossil strata. Skyscrapers, stadiums, sanitary landfills, and iPhones are not, at least not yet. They distinguish what Zalasiewicz calls the Urban Strata from strata below – and ominously but almost certainly, from future strata above.
It is sobering, but perfectly logical, to hypothesize that no trace of human habitation on the earth's surface will still be there 100 million years from now.
Our planet is too active, its surface too energetic, too abrasive, too corrosive, to allow even (say) the Egyptian Pyramids to exist for even a hundredth of that time. Leave a building carved out of solid diamond—were it even to be as big as the Ritz—exposed to the elements for that long and it would be worn away quite inexorably. (15)
The Pyramids?! I would have figured them for a more durable afterlife; I mean, can't they be seen from space, or something? But I was forgetting two key elements of Zalasiewicz's calculation. First, any human building starts to decay as soon as it's erected. We think of ancient buildings as able to weather any weather, but in fact the really old ones that remain unruined are often like the famous old axe that's had three heads and seven handles. Unless people continually rebuild old buildings, they disappear pretty fast. And for that matter, the Pyramids themselves are already considerably worse for wear, after just a few thousand years.
And that's the other thing: Zalasiewicz isn't talking about a few thousand years. He is talking about 100,000 thousand years. Too bad, Cowboys Stadium.
"Posthumanism" is a term of great current interest in the academy. It is usually employed in oblique or figurative terms. It can mean an intellectual movement that comes after and heavily revises the assumptions of humanism, or alternatively a way of thinking about earth as not revolving around the problems of a few little people, which don't amount to a hill of beans. But Zalasiewicz gives a very literal spin to the study of the posthuman. After we've hit the tracks, what tracks will still be there to show we ever hit them?
Zalasiewicz's view is frankly apocalyptic, and with good reason. It is as likely as not, in his view, that our demise will be brought about by our tendency to
combine high intelligence with breathtaking stupidity in equal measure: to be able to dominate the environment on the one hand and create a technologically sophisticated empire, but simultaneously to dismantle the systems that kept the Earth's surface stable and habitable. (217)The Urban Strata are likely to be defined by big cities (specifically, their cellars and cemeteries), perched on the edge of continents, preferably on sedimentary deltas. Amsterdam, Dacca, Haiphong, and New Orleans would be good candidates for finding themselves suddenly underwater and peacefully preserved by layers of fossilizing mud. And if the whole human race manages to obliterate itself around the same time – not via the long-feared bang of nuclear war, but the softer whimper of global warming – then the associated strata will also tell of deforestation, mass extinction, a temporary imbalance in world vegetation, and massive problems with the chemical cycles of ocean, soil, and atmosphere that have long regulated the blue marble.
The very longest view, of course, sees humanity as mostly a blip, and the planet easily reasserting its biosphere after this temporary irritation. (It's recovered from much worse than we've been able to do so far.) Zalasiewicz is full of comforting, if exceptionally long, views. A common meme, for instance, is that plastic will be around in pretty much its present shape and form for the rest of the history of the Universe. Most people imagine alien archeologists as disgusted as we are by a stratum of pop bottles. But Zalasiewicz notes that plastic itself will break down, not on human or even historical time scales, but over an easy hundred million years. Being organic, it will decompose into something very much like the oil it came from. For some reason, I find that a happy thought – though it's not going to make me give up my cloth grocery bags.
Zalasiewicz, Jan. The Earth after Us: What legacy will humans leave in the rocks? With contributions from Kim Freedman. Oxford: Oxford University Press, 2008.