An Introduction to Ardipithecus ramidus
Ardipithecus ramidus is an ancient hominin first discovered in 1994; over 110 specimens have been recovered from several different sites in the Afar rift of Ethiopia since that time. The 4.4 million year old creature was a tall, tree-climbing and bipedal fellow with a predominantly plant-based diet. They lived in a woodland environment and while they were certainly not fully human, neither did they exhibit climbing and walking strategies of modern chimpanzees or gorillas.
A. ramidus is tentatively believed to be ancestral to Australopithecus: but it is a million years older than Australopithecus afarensis (ca. 3.7 million years ago) and older than Australopithecus anamensis (3.9-4.2 million years ago). They were not tool makers—even Australopithecus didn't get into that until 2.5 mya, but Ardipithecus does have some traits carried on into Australopithecus.
But most surprisingly, A. ramidus walked upright on two legs while on the ground (called bipedal locomotion), and climbed on all fours along the branches of trees. That's surprising, because researchers had surmised that our ancestor would have more chimpanzee or gorilla-like characteristics—that it would spend most of its time swinging and hanging from tree branches.
Ardipithecus ramidus got a star treatment in Science magazine, with 11 separate articles written by nearly 50 scholars. This photos essay is a little taste of what was reported.
Sources and Further Information
White, Tim D., et al. 2009 Ardipithecus ramidus and the Paleobiology of Early Hominids. Science 326:75-86.