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Day 10 (July 5, 2011): Olorgesailie—the Big Picture

July 5, 2011


Olorgesailie has been a research site since 1942, when the great pioneers of East African archeology Louis and Mary Leakey first excavated and described handaxes and fossilized bones from here. Before that, J.W. Gregory, a famed geologist, reported handaxes while walking south to Lake Magadi.  Subsequent researchers, besides the Leakeys, included Robert M. Shackleton, a geologist who mapped the Olorgesailie sediments in wonderful detail, and Glynn Isaac, who directed the Olorgesailie excavations in the 1960s and later revolutionized the study of early human archeology by emphasizing the behavior of human ancestors rather than the classification of tools. Today, I am running my 27th field season at Olorgesailie.

So, after all these years, what has been discovered? Which questions have been answered? And, most importantly, which new questions have been asked?

Much of our studies here over the past 20 years has been to understand how the environment of the Rift Valley has changed over the past 1.2 million years, and the interplay between this change and how early humans survived and evolved.

Rick Potts points out to a landscape of cleared flat land with many excavated square pits spaced several meters apart in almost a checkerboard pattern
Rick points to several trenches at Hyena Hill, an area of what we call ‘paleolandscape excavation’.
But let me start by telling you about our main goal when my team first got to Olorgesailie in 1985. We began to address some of the big questions by developing a new method in paleoanthropology which we call the “paleolandscape approach.” Rather than excavating patches of sediments here and there and creating a spotty prehistoric record of random time periods, we decided to pinpoint specific layers of sediment and follow those layers across long distances to target where we excavate for fossils and artifacts.

So far, we’ve conducted hundreds of excavations throughout various time periods and geographic locations to create a continuous and gradual reconstruction of the past. The layer we are targeting now, at Site 15 for example, has over 130 excavations across 5 kilometers! At this point, we’ve targeted seven different time periods covering large areas of the Olorgesailie region – and about 500,000 years of time.

This work allows us to create a very detailed, but also holistic, picture of prehistoric Olorgesailie.

Of course, our team is not only composed of archeologists and paleontologists.  The work of geologists, which we will discuss more in the days to come, is vital to our understanding of the sediments themselves. Where did this dirt come from? How old are the layers in which our artifacts are found? Other geological research can include studying the chemical compositions of soils, or determining geologic events, such as volcanism, drought, or flood.  The team wouldn’t be complete, however, without paleontologists. Paleontologists help us understand the flora and fauna, or plants and animals, many now extinct, which have dotted this landscape and played a key role in early human survival. In the Olorgesailie fossil record, faunal remains are far more abundant than early human remains. In short, each excavation, even today’s work at BOK-2 and Site 15, is just another facet of a larger, bigger picture.

a black and white satellite image of the Olorgesailie Basin
The big picture of Olorgesailie – a satellite image showing the white sediments of the ancient lake (at the top) and the dark volcanic rocks of Mt. Olorgesailie (at the bottom).
We’ll look more at both the geological and paleontological aspects of our field research soon.

 (click here for more information on research at Olorgesailie, Kenya)