CNN) -- The oldest-known hominid skeleton was a 4-foot-tall female who walked upright more than 4 million years ago and offers new clues to how humans may have evolved, scientists say.

This sketch shows what a 4 million-year-old hominid, nicknamed Ardi, may have looked like.

Scientists believe that the fossilized remains, which were discovered in 1994 in Ethiopia and studied for years by an international team of researchers, support beliefs that humans and chimpanzees evolved separately from a common ancestor.

"This is not an ordinary fossil. It's not a chimp. It's not a human. It shows us what we used to be," said project co-director Tim White, a paleontologist at the University of California, Berkeley.

Ardipithecus ramidus, nicknamed "Ardi," is a hominid species that lived 4.4 million years ago in what is now Aramis, Ethiopia. That makes Ardi more than a million years older than the celebrated Lucy, the partial ape-human skeleton found in Africa in 1974.

Ardi's 125-piece skeleton includes the skull, teeth, pelvis, hands and feet bones. Scientists say the data collected from Ardi's bone fragments over the past 17 years push back the story of human evolution further than previously believed.

"In fact, what Ardipithecus tells us is that we as humans have been evolving to what we are today for at least 6 million years," C. Owen Lovejoy, an evolutionary biologist at Kent State University and project anatomist, said Thursday.

NASA' s Lunar Reconnaissance Orbiter has settled into a circular 31-mile-high orbit around the moon to begin mapping the surface and looking for minerals. Scientists have been expecting to find hydrogen,  which may mean there is frozen water on the moon. But if the early results are an indication of what is to come, the mission may end up generating more questions than it answers.

For starters, LRO has indeed found hydrogen, but some of the locations where it has turned up are places that, on the surface anyway, are not cold enough for ice to exist. 

"There is hydrogen near the lunar south polar region," LRO scientist Richard Vondrak told reporters yesterday, but added that it is not confined to craters that never see sunlight.