TOP Discovery 2009 - 1. Our Oldest Ancestor, "Ardi"

With her long, elegant fingers, 4-ft. frame and a head no larger than a bonobo's, it's hard not to feel a certain fondness for little Ardi, the oldest skeleton of a prehuman hominid ever found. Painstakingly pieced together from more than 100 crushed fossil fragments unearthed in Ethiopia, this female specimen of Ardipithecus ramidus (Ardi, for short) lived 4.4 million years ago and had remained anonymous until 1992, when her fragments were first discovered. After 17 years of research, a team of scientists led by Tim D. White from the University of California, Berkeley, published a comprehensive analysis of Ardi in October, in a series of articles in the journal Science. Among the team's revelations: Ardi was surprisingly unchimplike despite being the earliest known descendant of the last common ancestor shared by humans and chimps. Also, she was capable of walking on two feet despite living in an area of woodland and forest — a finding that downplays the importance of open grasslands to the evolution of human bipedalism