When Lee and I wrote The Skull in the Rock, his team had found
out quite a lot about sediba. But even as the book was being
printed, they discovered many more key fossils within a block of
stone they had not yet examined. And now, based on careful
studies of all of those fossils, we know much more about sediba –
much of it not what scientists had expected. On April 11, 2013, the
journal Science published six new papers, each of which told us
more about Sediba. Indeed, right now, we know more about this
species which was entirely unknown before Matthew Berger
stumbled and found the first fossil, than perhaps any other early
hominin. The six papers gave us new insight into how sediba used its
arms, walked, and chewed, as well as the shape of the species
teeth, rib cage and  lower back. I’ll spell about a few of those
observations here, but the really important point is what they all
add up to, together – I’ll get to that in a moment (cliffhangers are
always exciting).
      Because so much of sediba has been recovered, we are able to
piece together its shoulder area in great detail. As you can see in
this picture, which places sediba between a small modern woman
and a chimpanzee, its shoulders were positioned in a way that made
it seem it was always lifting or “shrugging” them. The team
believes that this arrangement, along with its long arms, made
sediba suited for climbing in trees, and that it would not have been
able to run well. We modern human can swing our arms when we
run, but the way sediba’s shoulder was built, it could not have done
that. Indeed another team was fortunate enough to have all of the
pieces they need to figure out exactly they walked. It would have
been strange indeed. When we stride, our heel hits the ground
first. When sediba did, the outside of its foot touched down first,
then they curled their foot to their toes – so they would have
looked a bit pigeon-toed. Our ancestors, it seemed, had to
experiment for a good while to figure out this walking thing.
      What comes across in each of the six studies is that sediba
was a mixture, a mosaic, of traits, some of which we now think of
us human, and some of which we now see as belonging to ages.
Sediba had a crazy quilt of characteristics that allowed it to live in
trees but use its strange two-footed walk to scamper between
them. This continually surprising mixture is the first main
conclusion of the articles. The second is a larger, and more
controversial point.
      Dr. Berger and the six teams who examined sediba are
beginning to see evidence that sediba more directly points
towards modern humans than some of the species that had
previously been sees as our ancestors. Indeed they have posed the
big question: is Australopithicus afarensis (Lucy) our ancestor? Or
is it possible that she was not, more a sideline precursor, while
indeed our lineage went through Australopithicus africanus (the
Taung Child that Lee writes about in Skull) and sediba? So far this
is a question, sure to be hotly debated. But is a question that
these new discoveries force us to ask.
      Stay tuned.