On first glance it looks like the skeleton of a lemur or maybe even a big house cat—but that first look is deceptive, as Ida is a 47–million–year–old fossil, discovered in amazingly good shape, that could be a key step in human evolution. Ida, as the fossil is called, is described as "the most complete primate fossil ever found and has characteristics found in later primates and humans." Is she the mythical missing link?

• Jorn H. Hurum, paleontologist at the University of Oslo.