Pushing It Back

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's a great HN thread I saved a few years ago that delves into this topic:

Was there a civilization on Earth before humans? https://news.ycombinator.com/item?id=16837120

The top comment by peatmoss:

> 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!

> 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.

There's an interesting recent PBS video on this topic: https://www.youtube.com/watch?v=opg6RO9cYnk

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.

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.

While metal objects can completely rust away over time, they leave weird shapes of high metal content soil shaped like the object.

If someone used rebar, you would detect strange lines of iron oxides in the soil. Those would be destroyed over large geological timescales.

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.

"The World Without Us"

https://www.amazon.com/World-Without-Us-Alan-Weisman-ebook/d...

A very detailed look at how long things last.

This is called the Silurian Hypothesis.