Dem Bones

A member of the venerable Leakey clan found some new fossils that suggest that human evolution was not as clean linear as many have thought (not that anyone serious ever thought that it was). Biologist PZ Myers over at Pharyngula has the details and what they mean:

[O]ne fact seems to be dominating the news about them, and is being consistently misinterpreted: the H[omo] erectus specimen is older than the H. habilis specimen, yet the most common models of human evolution have H. habilis giving rise to H. erectus which in turn was the progenitor of H. sapiens. Even the Nature news summary makes a big issue of this difference[:]

"Anthropologists have tended to see the evolution of Homo species as a linear progression, beginning with H. habilis and passing through H. erectus before ending up with modern humans."
...
These discoveries do not put any seriously held theories in doubt. They do nicely demonstrate that a linear progression is not to be seriously held.

Just as your mother's life most likely substantially overlapped with your own, the persistence of a parental species so that it overlaps in time with its daughter species is not a challenge to evolution at all. That's the case here; the authors certainly do not regard this work as casting any doubt on the evolution of humans at all.