Historical anachronisms as artifacts

An anachronism can be an artifact which appears out of place archaeologically or geologically. It is sometimes called OOPArt, for "out of place artifact". Anachronisms usually appear more technologically advanced than is expected for their place and period.

However, an apparent anachronism may reflect our ignorance rather than a genuine chronological anomaly. A popular view of history presents an unfolding of the past in which humanity has a primitive start and progresses toward development of technology. Alleged anachronistic artifacts demonstrate contradictions to this idea. Some archaeologists believe that seeing these artifacts as anachronisms underestimates the technology and creativity available to people at the time, although others believe that these are evidence of alternate or "fringe" timelines of human history.

If one envisions human technological advancement as being roughly parallel to the expansion and decline of human civilizations — that is, progressing in a "three steps forward, two steps back" sort of manner — then at least some (perhaps even many) apparent "anachronisms" are to be expected. A good example of this would be concrete, being used in the past by various ancient cultures only to be forgotten about and then re-invented at a later time by another culture, until the present, at which point the technology is employed globally and unlikely to slip into obscurity again.