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1999 Field Season: Day 22
July 16, 1999
Site B7/8-1 certainly looks like a place where early humans butchered a large animal, probably a rhinoceros. We have about 25 bones from the animal, including some of the ribs and vertebrae arranged in roughly the correct anatomical order. This means that the excavations are right where the animal died (as a rhinoceros is too large to carry as one big mass, and transporting it in pieces would disturb the anatomical order). And we have sharp stone tools indicating the presence of humans at the site. All of the bones and tools are buried in a soil that is about 780,000 years old. Soils are indicative of stable land surfaces, so it wasn't a river, and the bones and tools were not simply washed together from different places. All of the bones and artifacts were found in the top layer of the soil, so perhaps the objects that remained on the surface gradually sank into the soil whenever it became soggy...
But what could be wrong with our picture of this site? The interesting puzzles are in the details, and the details of this excavation pose some good challenges. For one thing, the stone artifacts lifted from the site today were taken from below the deepest extent of the bones. How did the animal get on top of the tools? Could it be that a rhinoceros 780,000 years ago just happened to keel over right on top of some stone tool flakes left behind by early humans, maybe left there after sharpening sticks to dig for roots and tubers?
For another thing, we have found evidence that modern plants and animals have also altered the original ancient soil. Modern roots are found throughout the site; many exploit the cracks in the fossil bones, and we have found both live burrowing insects, and egg cases within the fossil-artifact layer. The fact that present day roots and burrowing insects are found in an ancient soil containing fossils and stone tools is a complicating factor! Yet this could explain why some of the artifacts were found as much as 20 centimeters below (and above) the bones of the animal. They could have been repositioned through time as modern plants and animals churn the sediments (a process called "bioturbation"). So maybe the tools and the rhino were associated after all, in the original condition of the site.
In doing research like this, it is important to keep observing the details, and to keep asking questions. At Site B7/8-1, we need more clues. We'll extend the excavation later on. In the meantime, we will preserve the two trench walls, which have the fine layering of the stratigraphy recorded in them, for closer examination by our stratigraphy experts Kay Behrensmeyer and Peter Ditchfield.