July 9, 2004
John is just breaking ground at his site over in Locality G. While that's going on, I thought today I'd explain the process of excavation at Olorgesailie. Archaeological digs can be done in many different ways, depending on the age of the site and the kinds of fossils or other remains the researchers expect to find. Over the past 19 years at Olorgesailie, we've developed a system that allows us to be very efficient while gathering all the information we need. At GNF-1S, for example, the overburden (the sediment above our target layer) was first removed with a pickaxe and shovel. The overburden consisted of about 40 centimeters of volcanic ash. We knew from last year's excavation that there wouldn't be fossils or artifacts in this layer. But we used the pick and shovel to clear only about three quarters of the overburden. The last 10 centimeters are going to be removed by using a small awl and a hammer to pick out the sediment.
Once the excavators reach the layer that we think has fossils, they continue, very slowly, with awls and hammers and occasionally with dental picks. You can see in the top photograph Benard Mukilya using the awl and hammer. One tiny bit of sediment is removed with every tap of the hammer. The immediate goal is to dig in this manner to a depth of five centimeters. Each 5-centimeter depth is called a spit. Small flakes of stone or bits of bone are put into bags that are marked with the information of the site and spit they came from. Dominic Kateto is writing the information on the bags in the second photograph. The sediment from each spit is carefully swept up and moved to its own pile outside the excavation, so that the spits are kept separate. The sediment is later sieved to find any really small bits that were missed during the excavation.
Larger fossils and artifacts are carefully marked and left in place, while the sediment around it is removed. This process leaves these bones and tools on a small pedestal. As we remove sediments around these objects, we can find even more fossils and artifacts without losing the exact information of where the others were found. The photograph shows handaxes from site CL1-1 on their pedestals.
After nearly every 5 or 10 centimeters of digging, if fossils and artifacts have been found, I call for a "lift." This means a detailed, careful removal of the larger objects from their pedestals. In a lift, we assign a unique number to each specimen and then specially trained excavators who I call the fundis (Swahili for "experts") use a surveying instrument called a total station. They use it to precisely record the location of each fossil and artifact. As the item is picked up from its pedestal, I also use a compass to measure exactly the direction in which each object is sloping and the direction of the slope. Finally, each object is placed in a separate, marked bag ready to go back to the museum in Nairobi for cleaning, analysis, and eventually storage for future students and researchers to study.