Anthropologists are, among other things, detectives – piecing together evidence to work out how people behave and survive in certain conditions. Archaeology is anthropology of the past, so a proven timeline for dating archaeological artefacts is a great investigative tool. Dendrochronology supplies physical evidence for a timeline compiled through international data-sharing between practitioners. This fascinating branch of science provides anthropologists with accurate dates, and other information, and has roots going back millennia.
What is Dendrochronology?
Dendrochronology is otherwise known as tree-ring dating. Researchers take a slice from across a tree trunk, and gain information by looking at the distinctive rings formed by the annual growth of the tree. Each ring records a response to climatic conditions, and forms a unique timestamp matched on all trees in the same species and region. In modern technique, an increment borer is drilled into a tree or a wooden object and the resulting core is carefully withdrawn with ring patterns intact. Thus, a picture is preserved of the tree-ring sequence that can be compared to reference samples, or to drawings or photographs of samples.
Astronomer A. E. Douglass developed the process as a tool for analysis in the 1890s as he worked at the Lowell Observatory in Arizona. He used tree-ring dating from dead very long-lived trees and from wooden beams in the structures of old buildings to create a chronology for the effects of solar (i.e. climatic) variations. Douglass established standard techniques and procedures while developing the first long comparison data.
Dendrochronological information has been gathered by thousands of researchers donating and collating their results since the International Tree-Ring Data Bank was established in Colorado in 1974. The addition in 2011 of a Digital Collaboratory for Cultural Dendrochronology, based in Utrecht, provides a data library of historical wood analyses for use in Humanities research.