Beneath the seafloor, time does not always flow in a straight line — shells from creatures separated by half a million years can come to rest as apparent neighbors, confounding the scientists who seek to read Earth's biography in stone. An international team spanning eight nations has now brought clarity to this ancient confusion, demonstrating through the analysis of more than 7,500 marine fossils that the speed at which sediment accumulates is the dominant force shaping how organisms from different eras become entangled in the same layer. The finding does not merely refine a technical method