The identification of "Ardi" is a major breakthrough because her species was an early step in the process of human evolution. Scientists do not claim to know whether that Ardi's species evolved directly into modern humans, but it is an important branch on the family tree. Some others:
SOURCES: Science - AAAS, National Museum of Natural History's department of anthropology | Illustration by J.H. MATTERNES; Graphic by The Washington Post - Oct. 1, 2009