Olorgesailie 2004 Field Season

Posted on 2004-07-15 by Rick Potts

July 15, 2004

One thing we like to look for is whether there are any marks on the surfaces of the fossil bones we find. The photographs below show three bones we have found in the past few days, all with interesting marks on them. Fossil bones can be marked in many ways. They can be scratched by the teeth of carnivores or rodents who eat the animals or the bone. They can be scratched or smashed by the stone tools of hominins. They can be rubbed or scratched by sediment or gravel that is trampled or pushed into the surface of the bone. Or they can be accidentally scratched or nicked by the excavator's tools as they're being excavated. Can you see the marks on the bones? What do…

Posted on 2004-07-14 by Rick Potts

July 14, 2004

What happens to artifacts after they are exposed by excavation? I briefly described a lift last week, but I wanted to go into more detail. How we remove artifacts from their original position is a very important part of what we do here, since we're not only interested in the artifacts themselves, but also what other information about hominin behavior they can give us.In the process of excavating things and removing them for study, we inevitably destroy the ancient organization of things. So we have to be especially careful when gathering information. If we mess up in the records we keep, it's almost impossible to return, put the artifacts back in their original positions and see how they relate to the original sediments. It's kind of like…

Posted on 2004-07-13 by Rick Potts

July 13, 2004

The Geology Field School had their second day of class today, while Amanda tagged along to watch and learn. The students got hands-on training from Kay, who walked them through a part of the Olorgesailie Formation. Yesterday they stayed near the Site Museum, looking at the lowest (oldest) members, while today they looked at Members 3 through 14.What does a team of geology students see in the Olorgesailie Formation that's different from what archeologists might see? They see the same strata and members as anyone else, but they also learn about the geological process that formed the members and how each one is uniquely recognizable. Even for these already-experienced students, it was sometimes confusing because the members can look very similar, and many geological faults disturb the…

Posted on 2004-07-12 by Rick Potts

July 12, 2004

Mt. Olorgesailie is a huge part of our experience here. We wake up every morning and see it from our tents. It overlooks our camp and helps orient us wherever we walk. I've already described the things we find in the basin below, but what's up on the mountain?

The answer is: rocks! I mentioned earlier that the mountains within the rift are almost entirely volcanic, formed when the super hot magma within the earth erupted to the surface and cooled. There are many different kinds of volcanic rocks. We talked about pumice and ash, but there's also obsidian, which is a kind of volcanic glass. Basalt is a dark, dense rock that erupted repeatedly from Mt. Olorgesailie and nearby fissures. And there are several other…

Posted on 2004-07-11 by Rick Potts

July 11, 2004

Another Sunday rolls around, and the crew is taking a well-deserved rest. I'll go out with the Geology Field Course students for part of the day, and then hope for some quiet time in camp to catch up on reading and maybe some notes.While I was in Nairobi on Thursday evening, Amanda and Lynn got to spend dinner with Muteti. They asked about his life when he's not the foreman of our excavation crew. Like most of our crew, Muteti Nume is Mkamba, a person from the Kamba tribe, who live mostly as farmers southeast of Nairobi. They own large shambas (plots of land) on which they grow maize, beans, potatoes, and all sorts of vegetables, which they eat themselves. When asked why he didn't sell some…

Posted on 2004-07-10 by Rick Potts

July 10, 2004

I drove to Nairobi late yesterday and this afternoon accompanied Dr. Kay Behrensmeyer and the students of the Geology Field Course to Olorgesailie. It's their first night in the field. During the coming weeks, I'll let you know what they're learning about the geology of Olorgesailie.Before all that begins, I was eager to check the three excavations we started at the beginning of the season. Particularly interesting are Site 15 and CL1-1 because stone tools and fossil bones are appearing in both excavations.At Site 15, the excavators have uncovered a long depression or channel that runs diagonally across the excavation. You can see it in the photograph below: starting at the upper right, it goes under Benard Mukilya and ends in the lower left. The edges of…

Posted on 2004-07-09 by Rick Potts

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.…

Posted on 2004-07-08 by Rick Potts

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…

Posted on 2004-07-07 by Rick Potts

July 7, 2004

At Olorgesailie, we are surrounded by dirt! The dirt is under every step we take. It blows around and gets us dusty during the day. And the dirt is what we dig - it preserves the prehistoric tools and fossil bones buried under the ground.Dirt is also called sediment, a word we've used a lot so far in these dispatches. Much of our information about the ancient habitats where early humans lived comes from the study of sediment.Lynn and Amanda joined me on another geology tour this morning. We focused on the strata (the layers of sediment) that can be seen at our excavation sites AD5/7-1 and CL1-1. You may recall that on a previous day I used the term "member" when talking about the geology of…

Posted on 2004-07-06 by Rick Potts

July 6, 2004

On Tuesdays we always send a truck to Nairobi to get supplies - food and other necessities that should last us a week. King'ola, Francis, and Mutuku are the cooks and camp assistants who prepare food for the excavation team and researchers. They also keep our tents clean and our camp running smoothly. We've worked together for so many years that they know what food and supplies I like to have on hand. So yesterday, as usual, they filled out our supply lists, which are taken to the general grocery store, the butcher shop, and the vegetable market, where our orders are packed up in boxes for bringing to camp. It's important to get it right since our group depends on the food and other supplies brought…

Posted on 2004-07-05 by Rick Potts

July 5, 2004

The sweeping and sieving of loose sediment continues below Site AD5/7-1, where we discovered the early human cranium. There's a lot of interest in the geography of this site and in what it tells us about this particular individual.

In earlier periods of time, at sites you may have heard of like Olduvai, Hadar, and Lake Turkana, there are lots of fossil human bones that researchers have discovered. These bones are usually found buried along the ancient lake margin or in stream channels - in other words, in the lowlands where sediments are deposited and accumulate in layers. We long wondered, why is Olorgesailie so different? From 1986 to 1996, we had dug in nearly every area of the lowland basin, in almost every kind of…

Posted on 2004-07-04 by Rick Potts

July 4, 2004

The past week has been quite exciting - new excavations, the announcement of the hominin fossil, handaxes appearing in our excavations at site CL1-1 and now we all deserve a day of rest. I like to call Sundays the "Etch-a-Sketch" day, where we turn our thoughts over, shake them a bit, and start the week with a clean slate. We get an extra hour or so of sleep, and breakfast is served at 8 instead of 6:45 am. The cooks prepare a treat for us - French toast with golden syrup, which is, without fail, delicious. We then spend the day relaxing or catching up on work.I try to make sure that the food here is very good for all the visiting scientists, students, and the excavation…

Posted on 2004-07-03 by Rick Potts

July 3, 2004

Today was rather eventful, bringing many guests to the site. Early in the morning, we were visited by a very brightly colored helicopter, which flew in from Nairobi carrying a videographer. Last February, a British film crew had scouted the cliff where we set up our camp every summer. They liked the location so much that they had planned to use it for shooting a car chase scene - leading to the car diving off the side of the cliff! Last week, the film producer drove into our camp and was shocked to find our tents and dining area set up on the road that led to the edge of the cliff. I explained that we set up our field station every year here, and the producer…

Posted on 2004-07-02 by Rick Potts

July 2, 2004

Today, our paper was published in the journal Science. Each week Science publishes many papers in a whole variety of scientific fields. So the papers in this journal are always very short - ours is only 3 pages. The National Museums of Kenya held a press conference, where I gave a brief talk and answered questions from reporters and museum scientists. As you might expect, I've been asked a lot about the significance of the find.One thing is that very little is known about what the early humans in Africa looked like between about 1 million and 600,000 years ago, despite all the stone tools they left behind. In fact, the Olorgesailie fossil is the only one definitely dated to that 400,000-year gap in the African fossil…

Posted on 2004-07-01 by Rick Potts

July 1, 2004

Bernie is dusty and desperate for a shower after collecting samples of diatoms from several portions of the Olorgesailie Formation. His goal is to figure out the conditions of the ancient lake and how the lake changed through time. The diatoms are a terrific clue about this. They are single-celled algae that have a silica skeleton easily preserved in sediments. They are very small, many being <0.01 mm. When viewed under a microscope, diatoms fossils are incredibly beautiful, since their skeletons show diverse patterns of slits and holes arranged in intricate ways. It turns out that patterns help distinguish between the several thousands of species of diatoms. Bernie drew pictures of several species of diatoms common to the Olorgesailie Formation - see the photos at the bottom…