Correction to This Article
The article incorrectly said that if 99.99 percent of the world's 6.5 billion people died, 65,000 people would remain. The correct number is 650,000.
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Depopulation Boom

But then there's the unstated human ego at work here, navel-gazing and overstating our importance.

One wonders if dolphins -- one of the few animals that can recognize their reflection in the mirror, and are thus capable of narcissism -- daydream about an end to their species: "So, like, this gi normous tuna boat comes through with this huge net . . ." and then wonder what would happen to the ocean without them.

Without us, it'll certainly be quieter. No lawn mowers, no jet skis. Because, at the moment, there are no other animals capable of producing fire, the night will revert to what it was thousands and then millions and tens of millions and then hundreds of millions and then billions of years ago -- primordial ink.

There will be a lovely view of the stars.

Of course, none of this is exactly plausible, at least as shown here.

Rick Potts, director of the human origins program at the Smithsonian's National Museum of Natural History, points out that no global species of animal dies out in a flash. True, scientists believe that there was some sort of "DNA crash" in our species about 50,000 to 80,000 years ago, with the number of breeding-age humans thought to have dwindled to about 10,000 people, almost all of them in Africa.

But that "crash" occurred over thousands of years, and we seemed to have bounced back. A dramatic event -- say, a meteor strike capable of killing off the world's most adaptable animal -- would also have a disastrous effect on the rest of life on Earth, and would kill off far more species than just us.

That said, these daydreams are terrific at showing exactly how and why our creations would collapse without our constant tending.

Lights would start going off within hours (power plants run out of fuel), most subway systems would fill with water within days (the New York City system pumps out 13 million gallons of water every day) and dogs would quickly go feral (an assertion backed by how dogs in New Orleans responded after the evacuation in Hurricane Katrina).

Grass and weeds would grow through cracks in asphalt and on sidewalks and roadways, producing the seeds that will eventually overrun them. The power generators at the Hoover Dam will keep the lights on in Las Vegas perhaps the longest of anywhere in the United States. But those automated systems will eventually be undone, a dam operator explains in "Life After People," because of tiny mollusks that will eventually grow so numerous that they will block cooling pipes, and an automated system will shut down one of the world's engineering marvels. Most of our monuments -- the Eiffel Tower, the Statue of Liberty -- will collapse in 300 years or less, undone by rust and rot.

What will be the last of us?

Probably the things we jettison from the planet.

The National Geographic Channel says that our footprints, flag and television cameras on the moon will last millenniums. For Weisman, there are the 1970s-launched Voyager capsules with their sounds and sights of humanity etched onto a "12-inch gold-plated copper analog disk" contained in a "gold-anodized aluminum box." It holds diagrams of DNA and the solar system, pictures of children and cities, and 26 musical recordings, including Chuck Berry and an aria from Mozart's "The Magic Flute."

Scientists expect it to last at least a billion years but probably a lot longer, Weisman writes.

"By then, tectonic upheavals or an expanded sun might well have rendered any signs of us left on Earth down to their molecular essence. It might be the closest that any human artifact would get to eternity."

There are also, Weisman notes, our radio and television signals, beaming into space forever because radio waves just keep expanding until, at some theoretical point, they get so dispersed in the ongoing noise of the universe that they couldn't be distinguished anymore: "To the limits of our universe and our knowledge, they are immortal, and broadcast images of our world and our times and memory are there with them."

So, long after our lovely little blue planet is reduced to a lifeless rock, somewhere in interstellar space billions of years from now, there will be "Gunsmoke" and "The Twilight Zone" and "Gilligan's Island" and "Aftermath." Little specks of energy bearing witness that once, in a small corner of the universe, we stood upright, looked at the stars and contemplated the day of our own demise.

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