Wednesday, November 01, 2006

Leave nothing but footprints

If humanity disappeared today, how long would it take for all traces of us to disappear? Suprisingly little time.

Doom timeline
Click image for larger view.

I could argue with some of the details from the timeline. E.g. endangered species begin recovering "immediately"? That's simplistic thinking -- sure, the immediate pressure on them will be reduced, but they still have to survive the years or decades it takes for their habitats to recover.

Similarly, it is foolish to imagine that methane will disappear from the atmosphere in the short term. So long as there are vast prairies and savannahs with vast herds of grazers, there will be methane. And don't forget the fungi and termites.

But despite these flaws, it is humbling to realise that virtually all traces of humanity would disappear after a mere fifty thousand years. After 200,000 years, even the most stable of man-made chemicals will have decayed or transformed. With the exception of some of the more long-lasting radioactive waste, in less than a quarter of a million years there won't be a sign we ever existed. We'd be lucky to even leave a fossil or two. Possibly the last trace of humanity could be a few footprints and pieces of machinery on the Moon.

It took about a quarter of a million years to go from Homo erectus to Neil Armstrong on the moon, and it could take the same again for virtually every trace of humanity to disappear from the Earth. Half a million years from appearance to disappearance. It gives you pause for thought to remember that life on Earth is about four billion years old, old enough to have seen eight thousand non-human civilizations rise, fall and disappear. There is no evidence for any of these, and good (well, moderately good at least) reason to expect that there were none, but if there were, chances are we wouldn't know.

(Original source of the timeline:

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