Designed lifespans like "2-6 years for a cell phone" are a red herring. The notched logs in Zambia weren't intended to last to the present day either. A cell phone might stop functioning as a cell phone after 10 years or so, but it will be recognizable as an ex-cell phone for a long, long time after that.
There's an SF story I don't want to spoiler that includes a metal shipwreck getting buried in sediment and making it into sedimentary rock. Google suggests that over 20k ships were lost in WWII alone.
Even reduced to little more than rust and concretions, that will make for some bloody funny fossils in the future. Cars might only last 15 years, but scrapyards last a hell of a lot longer than that.
So for there to be no possibility of artifact survival, I think you need complete turnover of the rocks in the Earth's crust. The oldest rocks on Earth are found in the Acasta Gneiss in Canada, and are 3.58 to 4.031 billion years old.
For ruling out a prehuman civilization, the question of the maximum theoretical "resolution" that we can observe the Earth at might be more important than the survival of the artifacts. I reckon something always survives; the real question is can we find it? For example finding Ötzi was dumb luck... how many Ötzi's have we missed? How many peat bog bodies ended up as John Innes No3?
There was a study funded by NASA on the topic which made the rounds back in the day. Here is the Scientific American take: [1], here is PBS Space Time YouTube: [2]
The topic pops up now and again, most recently called the The Silurian Hypothesis. There are many articles in respectable sources on the subject, it goes beyond science fiction into literal science.
For example, you might wonder how long it would take for some large portion of the surface of the earth to subduct. I believe the answer to that question is in the paper discussed in that article.
No problem. From what I remember (thirty years ago!) at that stage in his career he was trying to stake out as many successful futurist predictions as possible, so the novels from around that time feel like excuses to shoehorn in lots of near-future "...and then there was a peaceful revolution in South Africa" stabs in the dark. Honestly, I found it tiresome. YMMV.
> This is one of my all-time favorite “what if” questions. Some years ago a friend of mine coily posed this same question to me: What does humankind make that would survive 60 million years into the future, and if some other advanced industrial civilization had existed 60 million years ago, how would we know?
It turns out my friend had put a LOT of thought into this exact question. Enough to do a masters in geology, his work ultimately making it into a high profile journal with writeups in places like the NY Times.
He started talking to various geologists about what might survive as telltale markers of our civilization. Buildings or structures of any sort? Ha! Statues and monuments? Maybe we’d notice the odd deposit or two of minerals.
After going through a long list of candidates, he settled on carbon cenospheres. These are little balls of carbon almost exclusively made in internal combustion engines as the result of aerosolizing fossil fuels. Sixty million years ago, our love of the ICE will show up in the fossil record as a light dusting of cenospheres covering the earth—contemporaneous with massive numbers of species going extinct due to mankind’s other influence.
And as my friend was telling me his story, this is where my hair stood on end. Sixty million years ago we see a massive species extinction... and a light dusting of carbon cenospheres covering the globe.
But we also see unnatural levels of iridium at the same point. And, while it’s hypothetically possible some industrial civilization was mining iridium and blanketing the globe with it, it’s more probable that the iridium was delivered by an asteroid.
But how would you know? So my friend, as part of his research, went taking samples of his cenospheres from around the globe. What he found was interesting: namely, the further one gets from the Yucatan (where scientists had already validated there was an asteroid strike), the cenospheres get smaller. The big heavy ones precipitated out of the air closest to the Yucatan asteroid strike. Hardly likely to be coincidence.
So much for ancient civilization this time around.
However, his work rewrote a critical understanding of the KT asteroid extinction event. Namely, we previously thought most of the carbon at the KT boundary was the result of giant forest fires ignited by the strike. However we now know that the strike must have aerosolized massive oil fields under the Yucatan at that time and set them ablaze.
Not a bad contribution to science starting from a sci-fi premise!
A major city will leave a pretty big mark, geologically. The structures themselves will fall, but the materials have a good chance, especially concentrated as they are..Lots of artificial stone (concrete), asphalt, metal, artificial materials, plus chemical contamination of surrounding soil. These are things we can detect in much smaller amounts in very old rocks. I'd guess it just needs to be lucky enough to be in a depositional rather than erosive environment for a while so the weather doesn't immediately sweep it away.
I always thought the telltale would be a thin layer of mixed metals in the geological record. Assuming the civilisation lasts a few thousand years then that's a very thin layer 60m years later. And it would contain a lot of iron, copper, tin, lead, etc all mixed together in that thin layer. It would look very weird from a geological point of view.
Definitely. There is no way a city like Tokyo or NYC leaves absolutely no evidence civilization existed 100 million years into the future if geology continues to change at the rate it has changed.
I feel the same, but I did stop short of directly claiming it. I'm wondering if in 60my, they might only have an infinitesimal trace, or get subducted or something. I still feel like the major cities can't all be in erosive environments or liable to get their crust recycled, or whatever other processes can fully annihilate them, but I don't know quite enough about geology to be confident over tectonic timescales.
Scifi side note: imagine a world so thoroughly altered that even the magma from subducted crust shows signs of civilization.
> One logical possibility would be written records of some sort, using a substrate that hasn't survived—prone to waterlogging or insects, modern paper would certainly not survive across tens of kiloyears
Sometimes impermanence is a feature, not a bug. I was always told by my elders: 'The Internet is forever'. Once you put things on it, it's hard for them to be removed. A permanent record of sorts. But over the years I've found many sites just evaporate with entire Library of Alexandria events occurring daily on the web. Yes, we have Archive.org which has mirror copies, but it doesn't catch everything.
And bit rot is useful too. After I die, I don't really want my precious data lingering around. Let it rot.
> There's some evidence of worked beads and jewellery going back up to 70ky; there's no reason to suspect that fabric may not be similarly old, or even older—it's simply labour-intensive to manufacture (so scarce to begin with) and doesn't last much longer than a human lifetime.
Think about all the hominids that came before us that were intelligent enough to have tools and make structures to live in. They survived over 500,000 years and left barely a trace.
And then look at the last 1000 years. And see how much we’ve destroyed and the plastic layer of garbage they’ll be able to decode 400,000 years from now.
An intriguing hypothesis suggests the existence of an advanced civilization 12,000 years ago, who potentially lived on a continent now submerged due to cataclysmic flooding (detailed in the Altai Flood theory on Wikipedia). This speculative and unverified theory suggests that the survivors of this civilization dispersed globally, and influenced monumental architectural works, like the Pyramids or Göbekli Tepe, as a mean to saveguard their knowledge. There is an english website (https://builders-of-the-ancient-mysteries.com/about-bam/) and a french book and movie.
This is a lot of speculation, but it is interesting to consider in the light of this article.
To add to this — Ancient Apocalypse is a very popular Netflix series that was released in 2022 that goes into detail about this as well. Wikipedia is extremely derisive about the documentary because archaeologists think Graham Hancock is a total crackpot. He’s also done at least two interviews with Joe Rogan. In the newest one he goes into great detail about taking DMT and seeing serpents and weird stuff, he’s a wild dude.
I'm just finishing Shaman by Kim Stanley Robinson. While he usually writes sci-fi, this one is about a group of very early humans. It is absolutely riveting, fascinating, and beautiful. I absolutely recommend this book for anyone who is curious about how early humans might have lived.
Stephen Baxter's "Manifold: Origin" novel also describes the potential lives of non-Sapiens hominins, including their inner thoughts. I'm not sure how well researched it was, and the whole thing definitely has a more science fiction than historical fiction background, but it was an interesting (albeit not a very happy†) read: https://en.wikipedia.org/wiki/Origin_(Baxter_novel)
† None of his books are. But they're still very good.
This doesn’t fit into the rest of the discussion above, but the Malazan series absolutely blew me away with a subplot (!!) about ancient hominids making epic sacrifices to allow modern humans to exist.
This is (a) set in a fantasy world (b) has zero bearing in any real archeological or anthropological evidence and (c) is meant to be entertaining fiction more than an investigation into how early hominids might have lived. And yes, there are lots of magic and dragons involved.
However, the creators of this world were field archaeologists and anthropologists and their instincts for telling stories spanning evolutionary time scales is absolutely unrivaled.
One of my favorite scifi/fantasy series as a child was set in our world, but in which things like magic & Baba Yaga were real, historical entities. I forget how their eventual disappearance was justified, but I loved it as a kid.
What's more interesting than rebar is the question of "how much rebar", a large enough industrial production and you're going to start modifying entire geological strata with chemical changes that might be able to be detected, depending what it is.
Maybe another take on the "how much rebar" question, there are hills that a future archeologist would have a hard time explaining how they disappeared.
I’m entirely agnostic on the existence of pre-ancient advanced civilizations. I do think however that, at least in the works that reach a general audience, archeologist, anthropologists, and so on might be getting a little too much mileage out of absence of evidence is evidence of absence.
