Yahoo is carrying this Reuters report summarizing an interesting find by some German scientists:

Star dust found deep beneath the Pacific Ocean has led German scientists to speculate that a supernova explosion 3 million years ago might possibly have helped bring about human evolution.

Unfortunately the article gets a point critically wrong while attempting to shore up its "supernova as evolution machine" premise. Hominids were fully bipedal long before the forests receded; this was actually one of the fundamental surprises Lucy presented us with more than thirty years ago. Not sure if this gaffe is the journalist's fault or the fault of the press release he or she was working from.

However, the recession of the gigantic transcontinental forests from Africa was extremely important in hominid evolution. Until that time, apes were a relatively successful genus, with perhaps as many as twenty or thirty species spread from southern Africa to at least northern India. When the forests started to depart, these species could chose only three paths: follow the forests, strike out onto the burgeoning savannah, or die.

Most picked the third option. Three of the four remaining species chose to follow the forests, while one succeeded in adapting to the harsh savannah environment. We are, ultimately, a spectacularly successful offshoot of an otherwise dead genera. It's interesting to find out just what, exactly, may have pulled the trigger.