Although at 4.4 million years old, the Ardipithecus ramidus is not old enough to be the ancestor is common to both chimpanzees and humans—but its body shape and stature is substantially different from its perceived descendant, Australopithecus. Her body mass is quite a bit larger than Lucy's, and Ardipithecus retains the ability to climb trees, something Australopithecus did not. That alone argues that when humans evolved away from apes, some of the earliest trends were to formulate bipedal locomotion, albeit as a part time skill. That suggests that apes took a different evolutionary trajectory than we did, beginning by the mid-Pliocene and perhaps earlier still.
Sources and Further Information
Lovejoy, C. O., et al. 2009 The Great Divides: Ardipithecus ramidus Reveals the Postcrania of Our Last Common Ancestors with African Apes. Science 326:100-106.
- Ardipithecus ramidus, the blog post, which has links to recent news stories
- Lucy, famous Australopithecus afarensis
- Hominin
- Aramis, Ethiopia
- Bipedal locomotion
- Stable Isotope Analysis
- Phytoliths
- Middle Awash
