Scientists have uncovered yet another link in the human evolutionary tree: a 2-million year-old ancestor with a mixture of humanoid and apelike qualities that allowed it to climb trees as well as travel large distances on foot.
Named Australopithecus sediba, the ancestor stood at around 4 feet and is equipped with an ape-like ribcage and a human-like spine. Both traits allow it to thread a middle ground between mobility in trees and ground.
"It is the perfect compromise of something that has the need to walk on the ground efficiently for long distances. At the same time, it is a very capable climber," said team leader Lee Berger from the Wits Evolutionary Studies Institute in South Africa.
Sediba's narrower ribcage allows for shoulder blade movement conducive to climbing, but the possible degrees of shoulder locomotion suggest that it could not swing its arms as we do while walking, meaning this creature probably didn't run over ground. Sediba's heel structure, meanwhile, shows that the creature walked with its feet pointed inward - something many of us would call "pigeon-toed."
"They probably couldn't run over longer distances, especially as they were unable to swing their arms, which saves energy," says Peter Schmid from the University of Zurich.
The findings are causing a stir due to the sediba's incredibly mosaic-like qualities. Sediba shares some characteristics with other Australopithecus, but at the same time exhibits tendencies found in our genus, Homo. Sediba could in fact provide a keyhole glimpse into a crucial point in time in human evolution.
The scientists based their discovery on fossils discovered in Johannesburg in 2008.
You can read the published findings in the journal Science.
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