Question for the floor

[andrewducker]

So, how long in the past would a previous civilisation of, say, Mesopotamian levels have had to be for their to be no remaining sign of it? i.e. for any bronze tools to corrode away to nothing, pottery to do likewise.

How long will it take until Stonehenge is worn down to nothing by the wind and rain?

Comments

[pseudomonas]

I think you're going to need to state environmental assumptions. Destroyed by a volcano ≠ buried in permafrost.

[cheekbones3]

Without major cataclysm, I'd say that human influence on the planet would be visible (or at least easily found or inferred) for tens of thousands of years (at least!). Stone buildings may only survive for a couple of thousand years (unless they're exceptional, such as large pyramids), but there are such huge works of engineering that I can't see being worn down for much longer (reclaimed land, dams, huge skyscrapers).

[birguslatro]

Oldest known ceramic...

http://en.wikipedia.org/wiki/Venus_of_Doln%C3%AD_V%C4%9Bstonice

Oldest known carving...

http://en.wikipedia.org/wiki/Venus_of_Willendorf

And considering their condition, it would appear that simple stuff humans can make could last a lot longer than 30,000 years.

Which doesn't answer your question, but perhaps fossil trackways do...

http://en.wikipedia.org/wiki/Fossil_trackway

So ceramics could retain their shape for millions of years, yes?

[bart-calendar.livejournal.com]

If you include tools pretty fucking long. In Ethiopia they've found tools more than two million years old. And if you want more civilized than that the Pyramids date back to 2060 B.C. or so.

The Lascaux cave drawings are supposed be something like 17,000 years old.

[danieldwilliam.livejournal.com]

I think it would depend on the conditions and the history. Some physical conditions preserve features much better than others. History has a role to play too. Lots of Roman cities are identifiable because post-Roman people took over their sites and built on top of them, preserving them as layers of different cities, whereas more of the Archaic Greek stuff was just destroyed in their Dark Age. Ish.

Also what you define as traces. Do you want to be able to describe aspects of the day to day lives of individuals or do you just want to be able to say somebody who was civilised but different from what is here now used to live here?

[nickys.livejournal.com]

Well, stone stuff lasts a very long time, so if your hypothetical civilisation used stone then it'd be a lot easier to find than if it was based on wooden or clay brick buildings.

Skara Brae, for example is about 5000 years old and pretty much completely preserved, whereas most archaeology from that era is stains in the soil which are generally to be the remains of post holes, and rusty masses which can be scanned to prove they were once tools...

[sigmonster.livejournal.com]

Pottery would take fossilisation much better than, say, a dinosaur egg, so the answer has to be in the hundreds of millions of years. Most of the objects wouldn't fossilise, of course, but I do wonder about some of the North Sea sites (unless we fuck them all up with repeated dredging).

[gonzo21.livejournal.com]

You'd need something to scrape the land clean, because tools/etc will last... well. As long as we know of there being homo sapiens and even earlier hominid species around.

There's no reason to s uppose that in millions of years time, there won't still be artefacts of human civilisations being dug up.

So what you'd need to obliterate the human record would be something like a glaciation event, to scrape the land clean and wind up depositing almost everything in the deep oceans.

There is no evidence of really ancient human fossil remains in those parts of the world that have been exposed to repeated glacial action.

[strawberryfrog.livejournal.com]

It gets less and less likely that traces would be found, but if conditions are right for fossilisation, the probably of detection never really gets to zero in less than hundreds of million years. Oldest vertebrate fossils from 450 million years ago "are rare and fragmentary"

[broin.livejournal.com]

A really clever take on this popped up on RPGnet. Someone wondered if there had been a dinosaur civilisation, if we'd be able to spot it. And sure, many materials would have broken down.

But if the dinos had embedded gemstones in their teeth, we'd spot that. So essentially, if we had tyrannosaur rappers, we'd know.

[philmophlegm.livejournal.com]

There are archaeological finds of Australian aborigine stone tools dated to 50,000 years ago. Aborigine oral tradition also includes references to animals extinct since that time. That suggests that a continuing culture is capable of maintaining knowledge for a very long time.

[pennski.livejournal.com]

What a fascinating question and set of answers. I'm going to be thinking of dinosaur rappers with a space program now.