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Humanities Now Blog

News and Highlights from Arizona Humanities

Archaeology’s Deep Time Perspective on Environment and Social Sustainability

By Allen Dart

What good is archaeology except to dig up and show off troves of trinkets? Is this “social science” relevant to modern society, to making our lives better?

Well, yes. The “deep time” perspective of archaeology and related disciplines is valuable for making decisions on how we deal with environmental change, natural hazards, and human adaptation today. Archaeology is a science that studies past human cultures by analyzing artifacts, living sites, and other features that people left behind on the landscape. By using these material remains to interpret how and why ancient societies originated, grew, and declined through time, archaeology identifies cycles of change over the lifespans of societies, thereby extending scientific observation of stability and transformation beyond all social memory. The archaeological record records a fuller range of environmental dynamics, such as natural hazards and climate change, than historical records do. Because archaeology and related disciplines provide such a deep time perspective that we cannot see in written histories, these areas of inquiry can help us learn how to adapt to the present by studying ancient peoples and environments.

In my “Archaeology’s Deep Time Perspective on Environment and Social Sustainability” presentation for Arizona Humanities, I provide several case studies showing how archaeology and related disciplines can provide guidance for modern humankind. One example is from deep-time records of ancient climates. Average annual temperatures measured with thermometers since 1861 (our earliest consistent thermometer records) show that temperatures rose markedly starting between 1905 and 1940, and accelerated significantly beginning in the 1970s. But without good written records of temperatures prior to 1861, how can we tell whether similar extreme-temperature variations also occurred before 1861, or whether the past century’s gradual rises in temperatures really are unusual?

Fortunately, early in the twentieth century, astronomer A. E. Douglass recognized that tree-ring patterns can tell us a lot about past climatic conditions because certain kinds of trees grow thicker annual rings during rainier years and thinner ones or no new growth rings in drought years. By matching the ring patterns of living trees with those of wood samples cut from older, dead ones, Douglass created a “dendrochronology” – a tree-ring time chart – that shows how tree growth in the Southwest reflects environmental conditions in any particular year. With help from archaeologists, who provided older and older samples of wood from archaeological sites, this dendrochronology now has been extended back to 322 BC, almost 2,200 years earlier than all historical records of thermometer-based temperatures.

How do the tree-ring and thermometer climatic records compare? The deep time environmental record archived in tree rings indicates that the past century’s trend of markedly increasing temperatures is unprecedented during the past 1,000 years. Is this something we need to be concerned about? Considering that a significant percentage of the Earth’s surface water is currently frozen in polar ice caps, glaciers, and icebergs, continuing average temperature increase will cause sea levels to rise several meters in the next 50 years. So yes, I think warming temperatures are something we should worry about.

This is just one of several examples I discuss in my Arizona Humanities presentation about how archaeology and related “deep time” disciplines can help modern society make more informed decisions for planning how to address environmental change, population growth, agriculture, and unanticipated adversities.

allen dart graphic

SB - Allen Dart in Cottonwood Canyon  near Lower Gila Box Canyon NM  WEBAllen (“Al”) Dart holds a master’s degree in anthropology from The University of Arizona and is a Registered Professional Archaeologist who has worked and volunteered in Arizona and New Mexico archaeology since 1975. He currently serves as a State Cultural Resources Specialist/Archaeologist with the USDA Natural Resources Conservation Service and as the Executive Director of the Old Pueblo Archaeology Center, a Tucson non-profit organization that he founded in 1993 to provide educational and scientific programs in Southwestern archaeology and cultures. Dart is a recipient of the Arizona Governor’s Award in Public Archaeology and the Arizona Archaeological Society’s Professional Archaeologist of the Year Award for his efforts to bring archaeology and history to the public.

 

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