Olorgesailie 2004 Field Season

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…

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…

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…

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…

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…

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…

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…