the.com/stone age

means The prehistoric period, stretching from roughly 3.3 million years ago until the advent of metalworking, when tools and weapons were made primarily from stone.

from Coined as part of the three-age system developed by 19th-century archaeologists (notably the Danish scholar Christian Jürgensen Thomsen) who sorted prehistoric artifacts by material — Stone Age, Bronze Age, Iron Age — to bring order to museum collections. The label stuck because it works: it names an era by the one technology that defined nearly all of it, long before anyone thought to smelt anything.