Sorting Time Without a Clock
Before radiocarbon dating, archaeologists needed a way to arrange sites in chronological order using only the artifacts they found. Seriation, pioneered by Flinders Petrie in 1899 for Egyptian pottery and formalized by James Ford in the 1950s for the American Southeast, provides exactly that. The method exploits a simple insight: artifact styles change over time in predictable, gradual ways.
The Battleship Curve
When a new pottery style is invented, it starts rare. It grows in popularity, reaches a peak, then declines as newer styles replace it. Plot the percentage of each type over time and you get a lens-shaped curve — wide in the middle and tapered at the ends — nicknamed a battleship curve. This simulation generates synthetic assemblages with realistic frequency patterns and lets you see the sorting algorithm arrange them into chronological order.
Typology: The Foundation
Before seriation can work, artifacts must be classified into meaningful types. Archaeological typology considers raw material, manufacturing technique, form, decoration, and function. A good typological system creates categories that are chronologically sensitive — types that actually changed over time — while filtering out variation caused by function, raw material availability, or individual craftsmanship.
From Relative to Computational Ordering
Modern seriation uses algorithms like correspondence analysis and multidimensional scaling to find the best ordering of assemblages in high-dimensional frequency space. These methods can handle dozens of types across hundreds of assemblages simultaneously — far beyond what manual sorting could achieve. Yet the fundamental logic remains Petrie's: styles change, and that change is the archaeologist's clock.