For a stronger argument, archaeologists would have to find fossilized remains of creatures that come before and after A. sediba in the evolutionary lineage, Berger told CNN in 2011.
Ian Tattersall, paleoanthropologist and curator at the American Museum of Natural History in New York, wasn't involved in the studies, but he told CNN in 2011 that it's unlikely we will discover a direct evolutionary path, over millions of years, from Australopith into Homo. Instead, it appears there were many forms of upright creatures -- natural experiments in evolution -- that coexisted at the same time.
The new analyses are based on remains from three A. sediba skeletons -- a young male, an adult female, and an isolated shinbone from another adult.
These remains came from a cave at the Malapa site in South Africa that lost its roof. Lime miners, about 100 years ago, blasted out big chunks of sediment from the area that contained these fossils. They were preserved in blocks of mud and rock that had set like concrete, Churchill said.
Researchers have not dug in the cave itself yet, but they have already seen more bones sticking out of the cave wall, Churchill said. Experts have recovered, from the same place, exoskeletons of insects, plant material and porcupine quills that still contain black pigment -- all from around the same time as A. sediba. Blocks of concrete-like material that have been recovered, but not studied, also contain more pieces of skeletons.
"We're going to keep recovering more and more of these hominins," Churchill said, referring to early human relatives. "I'm sure there will be more surprises yet to come."