Time was, fossils and a few stone artifacts were about the only means scientists had of tracing the lines of early human evolution. And gaps in such material evidence were frustratingly wide....

[Now] new finds have filled in some of the yawning gaps in the fossil record. They have doubled the record’s time span from 3.5 million back almost to 7 million years ago and more than doubled the number of earliest known hominid species. The teeth and bone fragments suggest the form — the morphology — of these ancestors that lived presumably just this side of the human-ape split.