Everything is approximate. Each new approximation improves upon the last, but it is still an approximation, based upon a balance of what we want, what we notice, and what the platform is even capable of.
Madness string 1199
The Chesapeake bay was once so full of oysters you couldn't sail in it enough. Natives regularly ate oysters so large that colonists said they used the shells as dinner plates - we've found oyster shells 7 inches long. But now, the biggest oysters are a fraction of that size, and if we had seen the original oyster population we'd call them critically endangered.