The skull and brain are small, about the size of a chimpanzee.It was bipedal on the ground, though not as well adapted to bipedalism as the australopithecines were, and quadrupedal in the trees.
The time of the split between humans and living apes used to be thought to have occurred 15 to 20 million years ago, or even up to 30 or 40 million years ago.
This species was named Australopithecus ramidus in September 1994 (White et al.
1994; Wood 1994) from some fragmentary fossils dated at 4.4 million years.
Most scientists consider this evidence that afarensis was still partially adapted to climbing in trees, others consider it evolutionary baggage. Brain size may also have been slightly larger, ranging between 420 and 500 cc.
This species was named in 2001 from a partial skull found in Kenya with an unusual mixture of features (Leakey et al. This is a little larger than chimp brains (despite a similar body size), but still not advanced in the areas necessary for speech.