Whatever Floats Your...Ancient Plant Remains: How Archaeologists Use Water to Help Sort Delicate Plant Remains

 This week we will look at how smaller plant material is recovered from an archaeological site, but first, it is important to understand that plant material is delicate and requires a specific set of environmental conditions for it to last in the soil. In most instances, an anaerobic environment will provide the best preservation. This is an environment that is lacking oxygen, and therefore lacks bacteria. Just like you and I, microscopic bacteria require oxygen, so there are less of them in an anaerobic environment. Without these little critters present, delicate plant matter isn't eaten away over time.

One of the most common plant remains found at sites is wood charcoal. Early people relied heavily on fire, and charcoal can be an important source of information. In fact, it is commonly thought that the lack of charcoal at a site is indicative of poor preservation, not the lack of fire during the site's occupation. Often larger pieces of charcoal are recovered during dry screening, which is the most common way to separate artifacts from soil. But how do archaeologists recover those little delicate bits that would slip through a dry screen? This depends on a variety of factors, from the type of plant remains found at the site, the research question, time constraints, budget constraints, and more.  But one of the most common ways to recover small bits of charcoal and other plant material (like seeds, or fruit pits) is using a process called floatation.

                                              Video of how floatation works (courtesy of 

                                                                  Science Friday) 

Floatation is using water to separate lightweight plant material from the soil through agitation, which allows the lightweight plant material to float to the surface. It is an efficient process that allows for rapid processing of a large quantity of material. There are a variety of types of floatation set ups, from DIY to commercially made machines. Again, the type used depends on a variety of factors and constraints. Floatation was first used in 1905 by German botanist , Ludwig Wittmack, to recover plant remains from adobe brick. But it was popularized in the 1960s after appearing in an archaeological publication written by Stuart Struever. Since then, floatation has become a staple for recovering delicate plant remains. It isn't perfect however, samples from very dry and arid climates sometime dissolve, but overall, it has helped archaeologists recover material that would otherwise remain a mystery, and thus has helped archaeologists piece together a more holistic view of the past.

Spring Has Sprung! What Plants Can Tell Us About the Past

 When you think of archaeology, plants may not be the most immediate thing that comes to mind, but occasionally, under the right conditions, plant remains are found at archaeological sites. Archaeology is full of sub-disciplines, which makes sense when you think about it. There is so much to learn about the past that no one archaeologist can possibly learn about or know it all. One of those sub-disciplines is archaeobotany.

 Archaeologists that study archaeobotany are interested in learning more about how people of the past interacted with plants. Think about what a huge role plants have in our modern life. The same, or similar, was true in the past as well. People ate plants, grew plants, use plant material to construct shelters and tools, and lived among various plants growing wild. Plant remains can also tell us about past environments, thus providing clues to what life was like for people in the past. 

Plant remains from the Lake Monroe Outlet Midden
(photo courtesy of the Florida Museum of  Natural 
History, University of Florida)

Plant remains are organic, fragile, and usually (but not always) small. They don't always preserve well at archaeological sites. It takes special environmental conditions for them to preserve and archaeologists have to take special care to recover these fragile remains on the occasions they are found at an archaeological site. Most of the time archaeologists only find a small sampling of the remains of the past. They only find the things that preserve well, such as stone and ceramics. But as we know, people are much more complex, and finding plant remains is a treat for archaeologists and a chance to gain a more thorough understanding of our past! Sometimes plant remains are small, like pollen (can you imagine!?), and other times they are large, like a dugout canoe. No matter their size, plant remains provide unique opportunities for archaeologists. 

Take a moment to look around you and make note of all the objects made from plants. Then think about how many of those objects would still be around 500 to 1,000 years from now. Probably not many. Now imagine someone in the future trying to piece together your daily life without having all those plant-based objects available to study. They probably would only be able to learn a fraction of what your daily life was like. That is why archaeobotany is so valuable to the study of the past. So this month, as plants are blooming and it is starting to feel like spring, we want to take a moment to talk about plants in an archaeological context. We hope you will join us on this journey. From learning how archaeologists recover plant remains to what they can tell us, it is sure to be enlightening!