There is evidence they have: > Based on the concentration of Fe-60 in the crust, Knie estimated that the supernova exploded at least 100 light-years from Earth

There is evidence they have: > Based on the concentration of Fe-60 in the crust, Knie estimated that the supernova exploded at least 100 light-years from Earth—three times the distance at which it could’ve obliterated the ozone layer—but close enough to potentially alter cloud formation, and thus, climate. While no mass-extinction events happened 2.8 million years ago, some drastic climate changes did take place. [1] [1] http://nautil.us/issue/22/slow/the-secret-history-of-the-supernova-at-the-bottom-of-the-sea http://nautil.us/issue/22/slow/the-secret-history-of-the-sup...