The Ardipithecus Ramidus (Ardi) discovery confirms the theory that our ancestors were walking upright long before they ever moved to the open savanna. Interview with team-leader Dr. Tim White.

Duration: 2 minutes, 58 seconds

Posted: October 5, 2009

Dave Micklos: I'm Dave Micklos of the Dolan DNA Learning Center at Cold Spring Harbor Laboratory. The world of paleontology was in the spotlight this week with the publication of a detailed description of a fossil of the oldest hominid ancestor discovered to date. Ardipithecus ramidus, or 'Arti' for short, lived 4.4 million years ago in what is now Etheopia; this is 1.2 million years older than the famous 'Lucy' fossil. Arti was female; she weighed about 110 pounds and was about 4 feet tall. Although she had a small brain and was able to climb trees, her body was adapted to walking upright; a critical attribute that sets humans apart from our nearest living relative, the Chimpanzee.

Perhaps the most significant part of the study, which took more than a decade to complete, was the detailed inventory of the plants and animals found along with Arti's remains. These showed that she lived in a wooded environment, not the open savannah where Lucy and her more recent ancestors roamed. I asked Tim White, a leader of the team that found Arti, what this all means.

Tim White: I think we’ve gone a long way to dispel the myth that humans originated on a savannah, and what we’ve learned since the discovery of Lucy with these earlier fossils from Kenya and (Chan) and Ethiopia is that they’re consistently found in woodland environments; not in open savannahs, and we can tell this because we have traces ranging from pollen and phytoliths in the plants to the seeds of the plants, to the fossilized wood, fossilized termite evidence. We have dung beetle balls that are fossilized, we have birds, we have rodents, we have all the large mammals that occupied these areas and we’re not just out there looking for human ancestors. We’re trying to build the ancient ecology from the traces that we can recover, and as we’ve done this with Artipithecus we realize that it’s a creature that lives in a woodland area, not an open savannah, and this runs all the way through its dental anatomy; it lacks the dental anatomy we see in later hominids like the Lucy species, more adapted to an open setting with harsher foods.

So it looks like hominids originated in a closed woodland environment, and so then your question of course naturally follows; what drove this? And it was the acquisition of bipedality, and that’s the answer that we want as well.

Dave Micklos: So in one stride, the Arti fossil challenges the notion that our ancestors first evolved in upright stature to exploit resources that were available to them on the open savannah. It appears that Arti was walking in the woods for hundreds of thousands of years before our later ancestors ever strolled out onto the African plain.