Map of the world divided into 7 regions, one for each billion inhabitants

I spotted this map on Twitter, showing the world divided into seven regions each of 1 billion people. The source appears to be National Geographic but it's not clear. (Update: it's be Reddit uset delugetheory)

CoiMgZEUsAIcvcGThis map is even more amazing, though rather crafty when you think about it: there are purportedly as many people in the red area as in the blue area.