July 16, 2011
We’ve had two productive days so far orienting ourselves to the many eroded gullies on the shores of Lake Victoria. Two of the most important areas of the Homa Peninsula are Kanam and Kanjera, located on the northern rim of the Peninsula. These two places have been the source of controversy ever since Louis Leakey, in the 1930s, collected a fossil jaw fragment from Kanam and skeletal remains from Kanjera – and concluded (without much investigation) that our species, Homo sapiens, can be traced into the Pliocene period, which now dates back to older than 2 million years.
It turns out that Louis had misidentified the sediment layers in which the jaw and skeletal remains were buried. In fact, the remains included recent burials into soils forming on ancient sediments. This is one of the reasons why it’s a very good idea for scientific projects to work in teams. In our case, groups of geologists, archeologists, paleontologists, and so on, all bring different areas of expertise and different types of observation to bear on a given question.
Our Smithsonian team’s long-term goal is to reconstruct an exact geological history of the entire Homa Peninsula. We also seek to understand when early human species occupied this region, how they lived, and the environments they encountered. Geology is crucial to these matters. That’s why I’m excited to have the geologists from China with me to see what types of interesting questions their areas of expertise can help to answer – especially about the dating of the sediments that contain fossils.
Two days ago, we made a brief excursion to the Kanam West gullies to see where Leakey picked up the controversial jaw, and to try to better understand the sediments in which our team had previously dug an excellent series of fossil bones ranging in age from about 6 million to 3.5 million years old. So far, though, no finds of early human bones have been found in that time period here. That time period is also older than the oldest known stone tools, which have been found in Ethiopia back to about 2.6 million years old.
Today’s goal was to visit the most important site our team, led by Tom Plummer, has unearthed – the site of Kanjera South. This site is located south of where Louis Leakey focused his studies. Over the past decade, our excavators found layers rich in stone artifacts and the bones of butchered animals (slicing marks made by stone tools were found on the bones). Early humans used the kind of stone technology that is, in fact, the oldest known – called Oldowan technology, which consists of simply chipped cores and sharp flakes. The digs at Kanjera South discovered the earliest signs of this technology in western Kenya. With the site dated between 1.95 and 2.0 million years old, Kanjera South provides the oldest definite evidence of early toolmakers eating meat as a long-term way of life. The site is also unusual in showing that early humans back to nearly 2.0 million years ago carried rocks for toolmaking over distances of up to 12 or 13 kilometers – a longer distance than at any other Oldowan site. Finally, the site also bears the oldest indication so far that Oldowan toolmakers inhabited a grassland environment. Kanjera South, in short, has quite a few ‘firsts’!
The question is, can we obtain an even more precise geological date for the site. Our visitors thought it’s worth a try, and collected samples of volcanic rock and ash to analyze with delicate instruments back at their research institute.
After a few hours, we ventured on to two other Oldowan sites that Tom has recently discovered. I was really impressed by the number of fossil and stone tools finds at these sites, and we hope to dig at both in the coming years.