Australopithecus sediba is a recent discovery of a new species that represents intermediate features of modern day humans and Australopithecus africanus. The discovery includes two well-preserved fossils dating back 1.95 to 1.78 million years ago, showing a mosaic of human and A. africanus characteristics. It is likely a descendant of A. africanus.
These new fossils, however, represent a hominid that appeared approximately one million years later than Lucy, and their features imply that the transition from earlier hominids to the Homo genus occurred in very slow stages, with various Homo-like species emerging first.
“It is not possible to establish the precise phylogenetic position of Australopithecus sediba in relation to various species assigned to early Homo,” wrote Lee Berger, a lead author of one of the Science reports. “We can conclude that… this new species shares more derived features with early Homo than any other known australopith species, and thus represents a candidate ancestor for the genus, or a sister group to a close ancestor that persisted for some time after the first appearance of Homo.”
Again, the new species is considered to likely be a descendant of A. africanus, but whether or not it is part of human lineage is less certain. Importantly, however, it represents at least a cousin that was evolving alongside our ancestors. (Phylogenetic relationships, in fact, are often based upon indirect ancestry.)
For more of the details about this discovery (such as the fact that it was bipedal or just how it was all so well-preserved), give Brian Switek’s post a look.