It’s a hundred million years hence and out-of-work actors from a small planet somewhere in the vicinity of Betelgeuse have finally made it to the Earth. What have they found?
Not us. Even statistically that’s unlikely – few mammals survive longer than ten million years and at the present rate of progress we’ll be lucky to make our millionth birthday.
Fortunately, the actors have brought geologists with them and that’s the premise of Jan Zalasiewicz’s The Earth after Us. I was disappointed that he didn’t dramatise the whole scenario; there’s an interesting job for someone else. Also, the first six chapters rehash the current state of geology and its findings. This is not a criticism, just a statement, and it was compelling reading anyway but the meat really started halfway through the book. What did we leave behind?
In all the layers of rock and sediment laid down in a hundred million years, our ten thousand is the merest sliver. Our best hope for immortality is the dislocation of a mass extinction such as marks the boundaries between the three modern eras. By modern I mean since more-than–microbial life started 650 million years ago, the latest being the one that did for the dinosaurs. We’re not at that point yet but the extinction rate is beginning to mark out a new period, a lesser geological division, one of about a dozen. The alien geologists will also be able to detect this.
The extinction tally so far will be less visible, especially concentrated as it is among the larger critters. They don’t appear as readily in the geological record as the billions of smaller organisms, which we may be unknowingly wiping out anyway. Let’s assume we do leave some dislocation, which causes the aliens to look more closely at our stratum. Will they find us now?
They will find a wholesale vegetation change, from forests to grass. Amazingly, pollen is so tough, abundant and dispersive that it will carry this record through the hundred million years. “A-ha!” will go the aliens, “another Ice Age. But one far more severe than any preceding it.” Then they’ll find paradoxical evidence of rising sea levels and that’ll make them scratch one of their heads and go looking even closer.
And that’s as far as I’ve read. So, either get the book yourself or check back here. I promise I’ll reveal all, or at least what I understand of it.