alt Hacker News> A quick search on "rock weathering depth per century"
That's a great illustration of what I meant. Of course an exposed rock consumes away in the space of a few millennia- this is exactly where the "Silurian theory" comes from. Yet it's also obvious that we have plenty of perfectly conserved rocks that are intact after hundreds of millions of years- i.e. fossils. Any small sculpture buried in clay can survive for an eternity.
> What do those findings tell you about the cognitive abilities and social organization
Skin? Like, with clothes on, or the shape of clothes? And shoes and hiking gear? Footprints with the shape of boots? Drawings "I LOVE YOU" in the sand? The shape of a coca-cola bottle buried in solidified clay? Come on...
> Any small sculpture buried in clay can survive for an eternity.
If it's made of granite, maybe. But how many granite sculptures have you seen? Sculptors tend to prefer prettier and more easily shaped materials, like marble and limestone. Those happen to be mostly calcium carbonate, just like bones and teeth, so section 1.2 in [1] (chemical dissolution in acidic environments) applies, along with section 1.3 and [2] (mechanical fracturing and dispersion during wetting-drying cycles).
Even if your sculpture was buried in a maximally favorable environment, it would not have stayed that way over tens of millions of years. 50 million years ago, the Himalayas were just starting to rise as India crashed into Eurasia, Australia was waving goodbye to a forest-covered Antarctica while the Americas, North and South, had yet to link up. At a rate of one ice age every 100k years, 500 ice ages separate us from those days. One is enough to raze half a continent and turn a muddy seabed into granite.
> Skin? Like, with clothes on, or the shape of clothes? And shoes and hiking gear? Footprints with the shape of boots?
This is extremely anthropocentric. A hypothetical "Silurian" civilization would obviously not have been human, and may have had no need for such things. Would bears endowed with human-level intelligence want to wear clothes and boots?
> Drawings "I LOVE YOU" in the sand?
Have any such preserved drawings in the sand been found from the ~200k years humans have been around?
> The shape of a coca-cola bottle buried in solidified clay?
See section 1.3 in [1], and remember that the time scale discussed in that kind of paper is a few thousand years, not tens of millions.
[1] https://www.sciencedirect.com/science/article/pii/S004896971...
[2] https://www.tandfonline.com/doi/abs/10.1179/0197136978063731...