Its like a fire in a movie warehouse.
And we're trying to reconstruct a catalog of the films, or even restore whole movies, from a few surviving frames of film stock buried in the rubble.
The archaeological evidence is buried, scattered, incomplete, and there wasn't that much there to begin with; these populations were small, dispersed, and living outdoors with very little technology. Also, those landscapes that best preserve fossils and artifacts are also the ones most likely to be avoided by early men.