The ages of humankind are designated by the material with which they made tools and weapons: stone, bronze, and iron. Remnants of these tools and weapons, found in archaeological excavations, are often the earliest evidence of existence in a place, especially before humans were able to express (and depict) themselves in words or art. Artistic depictions would follow, and then written ones, but both several thousands of years later. A wood, stone, or metal club, a stone or metal spearhead or arrowhead, a metal dagger or sword – and this appears to have been the progression – all could be used for hunting, likely their main function in pre-agricultural societies.