Spotlight Series: The Shawnee-Minisink Archaeological Site

“Well How Do They Know That?”: Shawnee-Minisink and How We Know What We Know About Prehistoric Peoples at One Archaeological Site.

The Spotlight Series is an occasional series that highlights interesting people, places, programs, and partner organizations working on historic preservation issues.

It is late summer or early fall about 10,000 years ago (give or take) and you have just returned to camp along a large river in an area that will one day be called Smithfield Township, Monroe County.  What’s it like?  The area is relatively open, much as it appears today, but it is not as dry.  The topography is rolling and there is water nearby—the upper Delaware River and Brodhead Creek are about 100 meters (around 328 feet) away.  Surrounding the camp is woodland consisting of white pine, birch, and willow with little underbrush.  You have arrived at the site at a fairly good time in terms of climate.  Following the recent ice age (which ended about 15, 000 years before the present), the climate began to warm.

As the warming continued, however, there was a rapid return to ice age-like conditions known as the “Younger Dryas,” (which ended about 11,500 years before the present) and was followed by more warming.  While this may seem too variable for our modern sensibilities, there is an upside: a warmer period followed by a cooler period followed by a warmer period has led to what we call a “mosaic environment,” which basically means that there is a rich variety of food resources for you to take advantage of, and take advantage of it you do.  Your diet consists of both plant foods, such as grapes, berries, and plums, and animal foods, such as fish and perhaps caribou.  On a more local level the late summer or early fall weather is characterized by warm winds from the south.  The one downside of this area, however, is that there are some large floods from the nearby Delaware River.

East wall profile from Unit 3

But wait, I can hear all of my non-archaeologist friends asking this—the same question I ask when I read certain articles from National Geographic, the same question my parents ask when I tell them about certain archaeological sites: “But how can you possibly know that?  You weren’t there.”  That is absolutely true, but, like detectives, archaeologists use the clues we find to figure this information out.  To start, we know the date the site was occupied based on the amount of carbon 14 in charcoal remains.  But what about the flooding?  How do we know that there were large floods along the Delaware River in the past?  We know that because there was a thick layer of sand covering the Paleo-Indian component of the site; this is important for some of the later inferences we make.  This layer was completely devoid of artifacts and had been deposited all at once, leaving a large flood as the likely cause.

Profile of hearth feature in Unit 4E; note the charcoal

But how do we know what the climate and weather was like back then?  For one, scientists can feed data from growth rings on trees, data from ice cores taken from the north and south poles, and geological data into computers to create large-scale models of climate in the past.  Clues from the site itself also tell us about more localized climate and weather patterns.  Remember that the site had been capped by a sterile flood deposit?  That means that the site would not have been contaminated by later deposits; therefore, whatever is found most likely came from the time period when the site was occupied.  For example, seed remains tell us what plants were present and we know what climates these plants prefer, so we can surmise what the climate was like.  In addition, the seeds can tell us about the relative openness of the site since we know how these plants tend to grow today.

We can also surmise the time of year since we know when these types of plants grow.  Scientists can study the remains of charcoal from fires, identify the species of the trees, and surmise the climate based on where these types of trees are found today.  People would get wood for their fires from nearby sources.  Remains of shells also can tell us about the relative wetness of the area in the past.  The location of artifacts can even tell us about the weather.  For example, the north side of one hearth was almost completely devoid of artifacts, telling us that winds were likely coming from the south—people don’t want to sit around the fire and have smoke blowing in their faces.  The plant remains and fish bones also obviously tell us what the people ate here.  No animal remains have been recovered from the site, but based on what animals would have been present, we can surmise which ones would have been eaten.

So this is how we know what we know about past Native Americans at one site in Pennsylvania.