Last night, in Shanghai, China, scientists from Wits University’s Institute for Human Evolution announced the discovery of fossils buried deep in a piece of rock about a metre in diameter. They are believed to be the remains of Karabo, one of the two Australopithecus sediba skeletons that were discovered at Malapa, in the Cradle of Humankind, in 2009.One is reminded of the arduous task that awaited Raymond Dart as he sat before the stone breccia that contained the first australopithecine to be discovered in South Africa. It took him seventy three days to pry apart the limestone to extract the remains.
Karabo’s partial skeleton was removed from the Malapa site, but the rock appears to contain more of his bones.
This is something that is often missed by the popular press and creationists: fossils are rare and complete fossils are even rarer. And, unlike the kind of archaeological work that goes on in neolithic or bronze age sites, human fossil remains are usually found in concretions—limestone or some other hard rock—and are very hard to extricate cleanly. In the case of Ardipithecus ramidus (or “Ardi”), the extraction took years because the bones were so brittle. Jamie Shreeve writes in National Geographic that as soon as bones were removed, they were doused with hardener to make sure they did not fall apart. Then, once they are removed comes the equally arduous task of trying to reconstitute the pieces. Complete skulls are rare and even the most complete ones have to be put back together. Once we have them, they are great tools for discovering how we came to be and the stages that got us here. But it takes a lot of work just to get to that point. It will be nice when we get the second A. sediba skeleton out to see how it compares to the one we already have.