Archaeology and Environmental Change at the End of the Ice Age

30 Days of Tennessee Archaeology 2016, Day 11

Jesse W. Tune
Department of Anthropology, Fort Lewis College

Environmental change –this term appears everywhere these days. It shows up in news media, social media, political debates, bill boards, TV and radio commercials, and even in archaeology. Terminology matters, and particularly for archaeology it’s important to talk about “environmental change” rather than “climate change.” This reflects the fact that it archaeologists are not just interested in past climates, but rather in understanding entire past environments (climate, plants, animals, rivers, landscapes, etc.), and how changes in the environment impacted the lives of past peoples. To address these questions we study environmental shifts over very long periods of time – centuries or even millennia. Much of my own research deals with environmental changes and subsequent human responses at the end of the last Ice Age (or Pleistocene).

The end of the Pleistocene was arguably the most dramatic period of environmental change that humans have ever experienced. Environmental records like ice and sediment cores reveal that this was a very chaotic time, as much of the Northern Hemisphere underwent the death throes of the last Ice Age. The climate began to warm up sometime around 18,000-16,000 years ago. Then about 12,900 years ago the world experienced the Younger Dryas (YD), an extreme and abrupt cold period that lasted some 1,300 years. The extent to which the YD affected humans is unclear. Undoubtedly, changes to human behaviors were directly related to the local severity of the YD. To understand how this chaotic period during the YD effected people living in Tennessee, we need to look at what people were doing before, during, and after the YD began.

One way to understand at how people lived in the past is to look at how tools (projectile points in this case) were being used. While there are a number of things that can complicate this type of analysis, comparing the length and width of points gives us a general idea of what was going on. When this length-to-width correlation is analyzed for points used before, during, and after the YD, a surprising pattern emerges.

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Comparison of length-to-width for Clovis, Cumberland, and Dalton points.

The length-to-width of Clovis points (used before the YD) and Cumberland points (used during the beginning of the YD) is very similar. This suggests that they were used and resharpened in very similar ways. However, the length-to-width of Dalton points (used at the end of the YD) is significantly different, and suggests that they were used and resharpened in very different ways.

 We can also learn about changes in behavior by examining how and when points were discarded. That is, did people discard them when they broke, or did they continually resharpen points until there was basically nothing left? Again, Clovis and Cumberland are nearly identical, while Dalton points are very different. Broken and resharpened Clovis and Cumberland points were discarded in about the same frequencies. Dalton points were discarded after being resharpened nearly eight times more frequently than when they were broken. This tells us that people using Clovis and Cumberland points made new points when they broke, while people using Dalton points held on to them and continued to resharpen them until there was basically nothing left.

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Frequencies of discard broke versus resharpened Clovis, Cumberland, and Dalton points.

Another way to understand how environmental change may have influenced changes in human behaviors is to look at what resources were used and where those resources were coming from. In this case, we can study the actual stone used to make projectile points. Much of Tennessee and the Midsouth is characterized by an abundance of chert (flint) suitable for making stone tools. The main chert types in Tennessee are Fort Payne and St. Louis, and their distributions essentially create an oval surrounding Nashville and Murfreesboro.

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Distribution of Fort Payne and St. Louis cherts in Tennessee.

Prior to the YD, Clovis points were being made in exactly the same frequencies from both chert types. During the beginning of the YD, two-thirds of Cumberland points were being made from Fort Payne chert, while only approximately one-third were being made from St. Louis. By the end of the YD, almost three-fourths of Dalton points were made from St. Louis, and only about one-fourth were made from Fort Payne.


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Comparison of chert types used for Clovis, Cumberland, and Dalton points.

At first glance it looks like this is a simple pattern to interpret. People making Clovis points had no preference for chert types, while Cumberland point makers preferred Fort Payne and Dalton makers preferred St. Louis. However, it may be more complicated (and interesting) than that…

If we consider where these two chert types are predominately found, then we can start to understand how people may have been using the landscape around them. Clovis and Cumberland points are found in similar distributions throughout the state, yet the types of chert used to make them are different. This may indicate that people making Clovis point were relatively unfamiliar with where certain types of chert occur, and were content using either raw material type. Later, people making Cumberland points would have been slightly more familiar with were certain chert types occur, and preferred to make their points from St. Louis material. Something different, however, appears to have been going on by Dalton times at the end of the YD. The distribution of Dalton points is much more limited that Clovis or Cumberland. In fact, in Tennessee, Dalton points are most frequently found in the same area where St. Louis chert is most prevalent. So rather than preferring to make Dalton points from St. Louis chert, people were simply using local stone resources to make points.

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Distributions of Clovis, Cumberland, and Dalton points in Tennessee.

So what does all of this tell us about the relationship between human behavior and environmental changes at the end of the last Ice Age? Basically, environmental changes at the beginning of the YD do not appear to have led to major changes in human behaviors in Tennessee – this may not be the case in other areas. Rather, it appears that significant changes occurred near the end of the YD when the climate began to warm up. Projectile point technologies trend toward being resharpened more extensively and used longer before being discarded. The territories where points were discarded appear to become smaller from Clovis-to-Cumberland-to-Dalton, while technologies became more focused on locally available resources.

Editor’s note: for a more in-depth discussion of this topic, see the recent journal article article “The Clovis-Cumberland-Dalton Succession: Settling into the Midsouth United States during the Pleistocene-to-Holocene Transition.”