More on Australopithecus sediba

Excellent little article by Carl Zimmer explaining the significance of the new fossils:

About 6 million years ago, our ancestors began to spend some of their time walking upright on the ground. Their descendants evolved into many different species, known as hominins. For the first 3.5 million years of hominin history, hominins all had the same basic kind of body: a chimp-sized brain (about one-third the size of our own), a snoutlike mouth, long arms with curved fingers good for climbing trees, and short legs that allowed them to walk slowly on the ground. Scientists call these early hominins australopiths.

Then something curious happened, starting about 2.3 million years ago. New hominins arose—members of our own genus, Homo. The australopith snout flattened. The hooklike fingers became smaller and more agile. By 1.8 million years ago, a species called Homo ergaster was about as tall as living humans, with long legs and stiff feet that were only good for walking on the ground. Its brain was now two-thirds the size of our own.

Paleoanthropologists have been trying for decades to learn more about how australopiths evolved into Homo. They've wondered where that evolution took place and how it unfolded. But they've found relatively few hominin fossils from that period.