This week the History Channel aired a two-hour special called LIFE AFTER PEOPLE, which explored how the world would change if the human race vanished. The program didn't get sidetracked by speculating on how our species might get wiped out. It simply postulated the instantaneous disappearance of all human beings. A rather unlikely prospect compared to a gradual decline, but that approach did allow vivid images of a modern city suddenly deserted. The probable scenarios at various intervals after our extinction were analyzed, beginning with "1 Day After People," going through a week, ten days, one year, etc., all the way up to 10,000 years.
How soon would the lights go out? In most areas, within a couple of days. Only the electricity from hydroelectric facilities such as the Hoover Dam, which doesn't need direct human intervention to keep producing power, would continue flowing for a long time. What would our pets do? Among those that could escape and attempt to live in the wild, small dogs and those bred for specialized but counter-survival traits such as short, pushed-in muzzles or stubby legs probably wouldn't last long. Cats were visualized as eventually forming thriving colonies in the vegetation-covered ruins of city skyscrapers, feeding on rodents and small birds. Both animals and plants from the wild would move into our emptied ecological niches with surprising speed (based on the example of how rapidly the wolf population in the American Northwest increased soon after a few dozen were released in
I was surprised at the pessimistic predictions of how soon our infrastructure would deteriorate without regular maintenance. A real-life example, a city in
It's not surprising that wood-frame buildings would succumb quickly to rot, termites, and lightning-set fires. But I was shocked to learn how much less “permanent” steel and concrete are than I'd thought. Moreover, modern concrete is less durable than the type used by the ancient Romans, quite a humbling thought. By a thousand years after our extinction, most of our cities would have become unrecognizable as such. "Tower and temple turn to dust," as the somber hymn says. More dismaying to me was the probable fate of our information storage media. Of course I knew electronic files aren't made to last, and I wasn't surprised that film, deprived of a climate-controlled environment, wouldn't survive long either. I'd expected books to hang around for alien archeologists to read, though. Not so, unless they're fortunate enough to be stored in a desert climate and protected from sunlight. Ironically, the stone and clay tablets of our remote ancestors will last longer than any of our advanced information technology.
I found this program sobering and yet oddly exhilarating. The image of the Earth starting afresh with nature reclaiming and obliterating all our works—only such monumental constructions as Mount Rushmore and the Great Wall of China are likely to survive mainly intact to the 10,000-year mark—fires the imagination. Last, the show speculated on our possible successors (assuming aliens don't drop in to explore and colonize, a scenario not mentioned on the program). Would one of the more advanced animal species evolve to fill our niche? Or was the development of intelligence such a one-time fluke that it's not likely to happen again on this planet? Chimpanzees were mentioned. That idea, however, overlooks the fact that chimps and other apes have undergone as many millions of years of evolutionary specialization as we have, since the era when an ancestral primate split into our two species. There's probably no turning back to the flexibility that would be required to enable them to evolve into a sapient species. At least, that's what I think from what I've read about primate evolution; I'm not a zoologist or anthropologist. The same principle applies to dolphins. Even if they have intelligence equivalent to ours, as some people believe, I can't see why our disappearance would inspire them to abandon their established niche in the ocean and return to land to build a technological civilization. So it would probably take far more than 10,000 years for any existing Terran life forms to develop into our technological successors. I'd put my money on the alien colonists.