* Claim of reversed human evolution sparks skepticism, interest:
Scientists' reactions have ranged from deep doubt to curiosity over last week's report of a mutation whose victims walk on all fours.
* Jurassic 'beaver' from China found:
A fossil shows mammals conquered the water far earlier than we thought, researchers say.
* Scientists report new kind of cosmic explosion:
Astronomers say they have detected a new type of blast that has sent scientists worldwide scrambling to telescopes.