July 8, 2004
John and I, along with Muteti, Bernard Kanunga (our assistant foreman), Amanda and Lynn, drove to Locality G. It's on the edge of the Olorgesailie basin in the younger sediments. It takes a while to get there - about a 15 minute drive followed by a 45 minute walk. John is interested in the Middle Stone Age, an African stone technology that appeared from about 250,000 to 40,000 years ago. The MSA, as we call it, followed the Acheulean. While the diagnostic technology of the Acheulean was the ability to make handaxes and similar large cutting tools, the diagnostic technology of the MSA is the ability to make Levallois flakes. Levallois technology was named after the site in France where it was first found.
The hominins who made Acheulean tools typically started with a very large flake or a core of stone. By knocking off smaller flakes, they shaped the original piece into the teardrop shape we call a handaxe. In the MSA, hominins had invented a new way of making tools, in which, instead of shaping the tool directly from a large flake or core, they first carefully shaped the core, and then hit one or several smaller flakes of a predictable size and shape, which were themselves useful as cutting tools. This gave the MSA toolmakers several advantages. First, they could make more tools from the same amount of rock as would make one handaxe. Second, the edges of these tools were generally sharper because they were not usually reused. And third, the toolmakers figured out that they could make flakes of many different shapes for many different uses, rather than one shape for a more limited number of uses. Even in the Stone Age, technology eventually got smaller and smaller. The small tool in the photograph is an MSA flake.
John and I looked at the sites where he and Alison dug last year. We wanted to decide what the course of action should be this year - where we should dig. John explained his reasoning process to Lynn and Amanda. He said that there were several factors that made some areas better to excavate than others. One factor is whether the site is datable. The shapes and styles of stone tools don't tell us very precisely when the tools were made, and archaeologists have historically been very bad at assigning dates to things. John was looking for a site near a volcanic tuff that can be dated by one of the radioactive isotope methods. Another important factor is whether the site occurs in a place undisturbed by flowing water. Artifacts that have been moved by water can't tell us as much about the habits of the humans who made them. In disturbed sites, we have a hard time telling exactly where or how those humans originally left the tools. Finally, John wanted a site where there is a good concentration of artifacts. Finding many artifacts together can often give us solid information about the variety of tools made by the hominins. I agreed with John's criteria, and added that especially here at Olorgesailie, "context is everything." John knew what I meant - it's also very important to figure out the ancient environmental setting in which the early humans lived and to connect the stratigraphy of the site to rest of the Olorgesailie region.
Having cleared this up, we spent some time walking around the area looking for possible sites, and decided on four. One will be the extension of "the sandwich site", known officially as GNF-1S (this name stands for Locality G, New Formation, first site, south). At this site, where excavations began last year, there's a layer with many MSA tools and some fossil bones eroding from between two datable tuffs. Nearby, we'll also dig a trench down the side of the hill to figure out how the sediments and tuffs of the sandwich site, on the opposite side of the hill, fit in with the larger picture. The third excavation will be on another hill, where tools have been eroding from under a volcanic tuff. These tools may be Sangoan, a uniquely African technology that seems to come between the Acheulean and the MSA. It's characterized by thick, rather unusual tools called "picks". The fourth excavation will extend a small site dug a couple years ago. It's another MSA site called "the green stone site," or GNF-2, where it appears an individual sat on a rock, still visible at the site, and made stone tools. Amanda will take charge of this small excavation, and she hopes to figure out what kind of stone tools the hominin was making.
All this decision-making led to a very busy morning, so there was only enough time to break ground at the sandwich site before we hiked to the truck and drove back to camp for lunch. Kay Behrensmeyer, a paleontologist and geologist colleague of mine from the Smithsonian, and Naomi Levin, a geology graduate student from the University of Utah, were waiting for me in camp. We spent the afternoon going over logistics for the Geology Field Course, which starts on Saturday. It's been a busy and productive day!