Megalodons are estimated to have gone extinct over 3 million years ago so that's the floor for how long bone can survive in significant numbers. They were huge

Megalodons are estimated to have gone extinct over 3 million years ago so that's the floor for how long bone can survive in significant numbers. They were huge carnivores so even though they constantly grew new teeth, the population was never that large to begin with compared to the billions of humans alive now, all leaving their durable refuse in a single contiguous layer. They may have been around for 1000x longer than humans but the billions and billions of tons of gold, copper, and other native metals will be obvious non-degradable remnants that will survive us for hundreds of millions of years. Any metal that can be found in its native form will survive for a very, very long time and the list of such metals is long. We already know that stone tools from archaic humans and apes easily survive for millions of years. The Keweenaw copper deposits [1] where copper is mined in boules and nuggets far larger than a strand of copper wire is about a billion years old. That's how long our bulk metal artifacts will survive, despite rigorous geological activity. Those artifacts already number in the hundreds of billions if not trillions. The only reason they don't already litter the planet like ancient pottery and arrow heads is that they're highly recyclable and reusable. > But I expected HN’s responses to be a touch more thought through. We've just been talking past each other which is par for the course for HN. [1] https://en.wikipedia.org/wiki/Copper_mining_in_Michigan https://en.wikipedia.org/wiki/Copper_mining_in_Michigan