A fundamental goal of archaeological research is to learn how old things are, either in absolute terms (i.e., a date range) or in relative terms (i.e., older than vs. younger than). Various techniques have been developed to interpret chronology, from the common sensical (things buried deeper are older than those above) to highly technical methods involving advanced nuclear physics.
The realization that deeper deposits tend to be older derives from early geological studies, and was first introduced into archaeology in the 19th century. This provides a relative chronology of earlier vs. later deposits. In early archaeological studies this technique was used to characterize cultural sequences such as Stone Age then Bronze Age then Iron Age.
Another technique for relative interpretations uses the seriation of artifacts, clustering the more similar as opposed to the more different, based on the theory that changing styles will evolve through time. This method is used on ceramics of Nicaragua to distinguish different types and then order them through time. When seriation is calibrated with absolute dates it becomes a very efficient and economical method to identify archaeological contexts by period.
During the Bagaces period (300-800 CE) ceramics continued with a red slip and decorations in black and occasionally white.
Dramatic changes occur in the ceramics of the Sapoá period (800–1250 CE) with the introduction of polychrome ceramics on a white slip, and also the use of shoe-shaped urns.
Nicaraguan ceramic seriation
The earliest ceramics in Nicaragua date to the Tempisque period (500 BCE –300 CE). Diagnostic types include Bocana Incised, Espinoza Red Banded, Rosales Black on Red, Schettell Incised, and Usulutan Negative.
Absolute dating gives a calendar date, although this is often only as date range. Indigenous calendars of the Maya and Mixtec, for example, recorded dates to the day –historical sources suggest that the ancient Nicaraguans used a similar calendar but evidence has disappeared. Tree-ring dating, known as dendrochronology, can also provide relatively accurate dates based on climate change, but again the tropical Nicaraguan environment does not preserve wood to the extent needed for this method.
Mixtec and Maya calendar systems.
The most commonly used method for absolute dating utilizes the decay rate of radioactive carbon (C14) atoms, known to have a half-life of 5730 years, to estimate the period since a living organism died. This is typically done with carbonized wood. When a tree dies it stops consuming carbon dioxide and the radioactive carbon begins to decay. By measuring the decay rate of an ancient sample, a date range can be estimated for how long before present the tree died. This can provide a range typically within 100 years of the actual event.
Innovative ceramics were introduced in the Ometepe period (1250 – 1525 CE) in addition to continuity of Sapoá types.