"Two million years ago, just as the Earth's primitive apemen were evolving into big-brained humans, a pair of supernovae explosions occurred near Earth.

Our planet was buffeted with blasts of radiation - with devastating effects. 'These supernovae would have blown away our protective ozone layer,' said Dr Narciso Benítez, of Johns Hopkins University, Baltimore

...for several hundred years the planet would have been battered by intense radiation. All sorts of mutational damage to animals' DNA would have occurred. New species could have emerged as a result. It is possible Homo sapiens may have been one of these."

The theory will be published in Physical Review Letters next week. [Alt. link] More on those supernovae here.