Great news for grasses Frans Lanting/Mint Images/Getty

Was the rise of humankind written in the stars? A nearby star exploding 8 million years ago might have triggered more frequent lightning on Earth. Wildfires ignited by that lightning could help explain the rise of east African savannahs – which many researchers think provided a vital backdrop for the early evolution of hominins.

The rise of African savannahs, beginning about 8 million years ago, has long been a mystery to biologists. They are dominated by plants called C4 grasses – but those grasses appeared 20 million years ago, long before they rose to …