Traces of civilization

[steuard]

Perhaps because I recently read Jared Diamond's book Collapse, I've been wondering just how lasting humanity's impact on the world has been. If we were to disappear today (say, due to a rampaging disease rather than some sort of violent catastrophe) and a civilization of intelligent cockroaches[1] rises in our place (or even just human survivors rising again), how much time would have had to pass for them to not realize that we'd been here? I'd say that a thousand or even ten thousand years is way too short a time (heck, the Pyramids will probably still be around that long). I'd guess that a billion years would be enough (wouldn't most of our continental material have been entirely re-made by then?). But that leaves an awfully broad span to narrow down in the middle.

Of course, the question is considerably more subtle than what I've described. For starters, I can think of three parameters to vary that would have a clear impact on the answer: (1) Time between our civilization's collapse and the rise of the next (as described above), (2) Technological level of the observing civilization (some traces such as skyscraper skeletons would be blatant signs, while others might require more advanced science to find: radiation levels or ice core analysis of other pollutants come to mind, or happening upon the US flag on the Moon), and (3) Point in our history when we disappeared (if those cockroaches were in our place today, would they realize that the Neanderthals were intelligent? Will any such signs be left a million years from now?). There are certainly even more factors to consider than that, but these three seem like a bare minimum.

I have a habit of wondering what we'll leave behind when and if we go, or how we could preserve our knowledge and a hint of our culture against catastrophe for future societies. (That's why I quite enjoyed Orson Scott Card's book Pastwatch, even though it's not that high on my list of "good" books.) But of course, this line of thinking also raises the natural question, "How many other times might intelligent life have arisen on Earth in the past that we just haven't noticed?" After all, who's to say that we aren't the cockroaches?


[1] All named "Squa Tront", for some reason.

Comments

[akjdg.livejournal.com]

As you state, it depends on how hard you look. To the causal human observer equivalent, I think most of our footprint would be difficult to discern within only a few hundred years. This would vary of course, by location, but consider:

1) We didn't realize the full scope of the Maya civilization until really quite recently. Turns out all those bumps are pyramids. Go fig.

2) Similarly, "1491" is a refreshing look at pre-columbian American civilizations, and suggests that the Americas were extensively, uh, terraformed at the time of contact. The book alleges, supported by acedemia somewhere, that the buffalo hordes of the plains were a sorta-farm run amok after the local peoples were killed off by european diseases.

3) 1491 also asserts that much of amazonia was more garden than jungle, extensively planted and groomed to suit the human palate to an extent that would not be expected of a truly wild jungle.

I highly recommend '1491' if you liked 'Collapse' - very different book, but it is broadly on topic, and a fascinating read. It's like reading the human history of half the planet for the first time. It also probed (at least for me), the true meaning of what our society considers to be 'wild' and the objectives of the 'environmental' movement. If the american pristine wilderness ideal was really just an overgrown and untended continental garden after 2-300 years of neglect, is it really so very important that we protect that? More fundamentally, why does there need to be such a distinct line between wilderness and development?

but back to examples:

4) Whilst performing recon for a hydro this summer, I was looking for a road shown on a ca. 1950s USGS map in the local mountains. I had crossed it two times before I saw it for what it was. A more trained eye would have spotted it immediately, for the road had become the ribbon of thickest alders amongst the willows (road cut = fresh soil and full sun = happy alders). There was a sidehill road cut still there, once you looked. The road bed had become a thicket of alders and, due to the local surficial geology and vegetated mat, something of a marsh due to lack of draining soils. This is after 50-60 years of abandonment.

After such a brief time, most structures would still stand. Wood framing, in AK, would be hard to spot in, 100 years? - it would certainly have collapsed, but might still be a pile of rusty nails and wood after that much time - might have a hard time seeing it under the brush, though. Steel structures would fail pretty quick (decades) once the building envelope was breached, exposing the structural core to the elements. Concrete degrades within a few 100s of years, depending on many factors. The truly lasting edifices, as you point out, would be the massive earthen or stone civil works.

If you looked closer with a scientific eye and instrumentation, our footprint would be evident for 1,000s, 10,000s of years, and beyond, certainly to the limits of our own paleoclimatological abilities.

I don't oft consider the legacy of our footprint after an extinction, but I do oft muse how one might preserve, protect, and pass on knowledge when our civilization collapses. It's an easy thing to imagine when in a rural Alaskan village with a population from 35 - 500 and 50 miles from the next dot on a map.

[kuddliphish.livejournal.com]

Depending on the type of civilization that followed us, they may not recognize even "obvious" traces. If they build only underground, for example, it may not occur to them that the Pyramids are anything but a natural feature of the desert. Also if enough time has passed (even a few thousand years, I would say) then the civilization is likely to blame any sign of our existence on its own fore-bearers. For example, whenever we find new cave drawings, or other signs of ancient intelligence, we assume it was made by humans, not some other type of intelligent life.

[coldtortuga.livejournal.com]

For example, whenever we find new cave drawings, or other signs of ancient intelligence, we assume it was made by humans, not some other type of intelligent life.
!! You know, I never thought of that...

[kirin]

It's an intriguing point, but it an alternate explanation would sure have some hoops to jump through. We have enough of the fossil record to make it seem unlikely that there was much of anything (that we'd recognize as a living thing anyway) outside of the apes/monkeys line that even had opposable thumbs - which sure make painting easier. To get around this it seems like you'd have to posit something as far-out as an intelligent slime-mold (which wouldn't leave a fossil record) or something like a highly motile and intelligent plant (which we just might not recognize) or something even odder. Not impossible to be sure, but it still seems like there'd be some clues.

And of course they could be made by aliens or energy beings or something, but it seems like begging Occam's Razor when there were, in fact, regular old hominids around that would be perfectly capable of making them.

[akjdg.livejournal.com]

Y'know, I saw an intelligent slime mold once. Tried to capture it for science, but those things are faster than you might think.

:)

[kirin]

Perhaps it was heading off to a rendezvous with a super-intelligent shade of the color blue?