Olorgesailie 2004 Field Season

Posted on 2004-07-30 by Rick Potts

July 30, 2004

In Locality G, where we've discovered Middle Stone Age sites, there's one site in particular called the Green Clay Site. A portion of the site was excavated two years ago. Amanda and one of our crew members, Vincent Kimeu, have renewed the digging at this site, and they've already unearthed several more MSA flakes. What's intriguing about this site is that all the flakes seem to have been left there at once, not over a period of many years. They're all from the same kind of stone, they're clustered in a small area, and there's no evidence that water or other forces disturbed the site. Even the tiniest flakes are present in the green soil, which is the best sign that nothing was disturbed after early humans…

Posted on 2004-07-29 by Rick Potts

July 29, 2004

John and Alison left this afternoon to meet their children, who happen to be visiting Nairobi. They'll all go on a safari together to see the famed animals and landscapes of Kenya. While they're gone for a few days, work is continuing in Locality G. The excavators have uncovered many more stone tools that belong to the Middle Stone Age (MSA), and survey by John and Alison has uncovered evidence of Sangoan tools lying on the surface of the eroded slopes. As I mentioned before, the MSA is characterized by small, specially-shaped flakes, while the Sangoan (the technology between the Acheulean and MSA) is characterized by three-sided picks and large, crude flakes. You can see large Sangoan tools at the top of the photograph, and small, fine…

Posted on 2004-07-28 by Rick Potts

July 28, 2004

Today was the last day of the Geology Field Course, and this morning I was able to listen in on a few of the students' final presentations. One project they've been working on during the past three weeks is to compare the geology and fauna of lower Member 11 between Locality A and Locality B. As you may recall, we divide up the Olorgesailie region into localities, with Locality A in the central part of the basin, and Locality B nestled close to the foothills of Mt. Olorgesailie to the south.Kay has taught the students the basics of how to record each geologic layer, and a really fun part of the course for the students was the chance to look for fossils in the two localities. Lower…

Posted on 2004-07-27 by Rick Potts

July 27, 2004

One of Al's colleagues at the Berkeley Geochronology Center, Warren Sharp, joined us to help with the dating. Warren does a slightly different kind of dating from Al, but I'll describe that later. He, Al, Kay, John, and Amanda spent today walking up the Ol Keju Nyiro, the name of the river that runs through the Olorgesailie basin. The Ol Keju Nyiro is dry most of the year, including the present dry season. Even though Olorgesailie has been explored for about 60 years, there's always more to learn, especially about the geology. Al, Kay and Warren were looking for places to take new samples to get dates from the youngest strata in the Olorgesailie region. Meanwhile, John and Amanda were looking for new areas that may be…

Posted on 2004-07-26 by Rick Potts

July 26, 2004

My good friend and colleague Alan Deino joined us this weekend and spent some very busy days walking around the basin looking for new tuffs to sample. I already described how we date tuffs using the argon-argon method, and how useful it is for archeologists. I didn't mention, though, that not all tuffs can be dated with this method. In order to get a good date from a tuff, you need to have large crystals of feldspar (a kind of mineral that collects argon). If there are no feldspar crystals in the tuff, or if the crystals have been damaged or contaminated, you can't date the tuff.

What is the use of an undatable tuff? Well, it's not a dead loss - you can still use…

Posted on 2004-07-25 by Rick Potts

July 25, 2004

Another Sunday rolls around, and the crew is off at Magadi. I took our guests to the Site Museum to show some of the stone tools that John and Alison have recovered, and to give them one last tour before they head off to Nairobi later today.This morning we were visited in camp by quite a few local people. They requested lifts in a vehicle to get water, to visit a local medical clinic, and to get to a hospital a little further away. We're happy to get these requests since over the years we've built a good relationship with the local Maasai. We use their land for our camp and excavations, and they know we're willing to help them with our vehicles and to give a…

Posted on 2004-07-24 by Rick Potts

July 24, 2004

Last night, we had the pleasure of welcoming several visitors from the Smithsonian Institution to our camp. Dr. David Evans oversees all scientific research at the Smithsonian, and Dr. Cristián Samper is the director of the Smithsonian's National Museum of Natural History. Dave's wife Eva and their 16-year-old son Tyler, and Cristián wife Adriana were also here. This was their first time to our field site, and they enjoyed seeing a Smithsonian field operation in action.

As we toured the excavations, they were filled with questions - and we were all filled with excitement as we saw new concentrations of handaxes coming out of the CL1-1 excavation, and fossil bones of a zebra emerging from the sediments of Site 15. We went searching for fossil plants…

Posted on 2004-07-23 by Rick Potts

July 23, 2004

I mentioned a few days ago the fossil animals found in the Olorgesailie basin, and that they differed from their living relatives. There is another aspect to the change in animal species that I didn't mention - through time, certain species disappeared from the valley, not necessarily because they went extinct and were replaced by another similar animal (like Elephas recki replaced by the living African elephant Loxodonta africana) but because the environment changed dramatically.We first noticed this pattern when we compared the species discovered in Upper Member 1, Lower Member 7 and Members 10 and 11. The predominant species in Upper Member 1, dated to 990,000 years old, were zebras. In Lower Member 7, at 900,000 years old, the two dominant species were the large baboon…

Posted on 2004-07-22 by Rick Potts

July 22, 2004

As I noted yesterday, the early humans of Olorgesailie knew a lot about the rocks they used in making tools. But one question I'm always asked is, how was the handaxe used? What were they used for? Many people expect me to answer with one very specific use, much as we usually use a fork or a knife for one particular purpose only. The handaxe is intriguing because the same shape of tool was made for over a million years, and we find them over wide areas of Africa, Europe and Asia - in many places where the hominins of that time had spread. You can see in the photograph how the handaxes of Africa, England and, India all have a very similar shape, even if they…

Posted on 2004-07-21 by Rick Potts

July 21, 2004

I've mentioned several times that much of our work here is to discover what we can about the behavior of early humans. I described a few days ago that the hominins made stone tools largely out of very local rocks. About 98% of the Acheulean tools are from rocks found within 5 kilometers of the sites. You may recall that, when we put all the clues together, we realized that the hominins were probably not trading for other, rarer stone materials. Rather, the groups moved occasionally from one area to another, and brought small bits of distant rocks into the Olorgesailie area.Another thing we've noticed is that the toolmakers preferred some types of stone material over others when making their tools. We've identified 14 different types of…

Posted on 2004-07-20 by Rick Potts

July 20, 2004

I like to think of early humans as the very first geologists. They liked rocks, they hit them, they used the results, and they knew a lot about the properties of different rocks. The geologists on our project take that knowledge many huge steps further, such as figuring out the age of sediments. We also need to name the geologic features we see to communicate with one another.OK, then, for today, more geology! I'll tell you about the differences between the New Formation, where John is working to uncover Middle Stone Age tools, and the Olorgesailie Formation, where the other excavations are uncovering Acheulean artifacts.The Olorgesailie Formation is the name of the fourteen members we've talked about in previous dispatches. It was formed during a time when…

Posted on 2004-07-19 by Rick Potts

July 19, 2004

I bet you realize by now that geology plays a tremendous role in all of our studies here. I like to tell my students (and fellow researchers), much of the exciting evidence of human evolution comes from the ground - so we better know our rocks and sediments.The geology field school visited Locality G today, and spent several hours exploring the differences between the New Formation in that area and the Olorgesailie Formation. As you may recall, Locality G is the low-lying area of the Olorgesailie region to the southwest, and it contains Middle Stone Age sites currently under excavation. These MSA sites are found in the New Formation. There's a lot of work to be done, starting next week, to figure out the age of the…

Posted on 2004-07-18 by Rick Potts

July 18, 2004

I'm sure you've gathered by now that we live in tents in the African bush - grassland, bushes, and woods as far as the eye can see. It's a long way from city noises and lights. And we don't have regular electricity and running water near our camp. In fact, you might wonder how we're able to write these dispatches to you if we don't have electricity. We have to be a little creative and resourceful, and often very patient, in order to live here.We do have one advantage as far as electricity is concerned. We are very close to the equator, so the sun is stronger throughout the year than in the higher latitudes of either the northern or southern hemispheres. It's an ideal place for…

Posted on 2004-07-17 by Rick Potts

July 17, 2004

Kay, John, three students, and I spent the morning in Locality G discussing the geology of the area. Our reason for visiting was to see if we could figure out how the volcanic tuffs relate to the excavation at the Sandwich Site. This site is named for the fact that it's sandwiched between two tuffs. I realize I mentioned tuffs earlier and their importance in dating a site, but didn't get to describe them.

Tuffs are layers of old volcanic ash. We see them as grey layers in the strata. The volcanic ashes came from eruptions. They were then carried over the landscape by wind and the force of eruption, and in some instances they were carried by water to where we see the layers of…

Posted on 2004-07-16 by Rick Potts

July 16, 2004

Many of you have read news stories or seen television shows about the animals of Kenya. Lions, hyenas, elephants, zebra, antelope, baboons, and ostriches define Africa to many people around the world. When you think of human ancestors walking across the landscape here, you may imagine they were eating antelope and scaring off lions. But how realistic a view is this? You know from our earlier dispatches that a different species of hominin lived here 900 thousand years ago or so. There were also different species of animals that lived here that long ago.Part of our purpose in uncovering fossil bones is to identify which species of animal they came from. Many of the bones we see are from species that are now extinct, just like the…