Ancient supernovae may have accelerated evolution on Earth

http://www.extremetech.com/wp-content/uploads/2015/12/supernova-head-640x353.jpg 640w, http://www.extremetech.com/wp-content/uploads/2015/12/supernova-head-672x371.jpg 672w, http://www.extremetech.com/wp-content/uploads/2015/12/supernova-head.jpg 1344w" sizes="(max-width: 300px) 100vw, 300px" />Two previously known supernovae may have affected evolution on Earth, and could even have driven a mass extinction millions of years ago.