LiveScience: Human beings have altered the Earth so much that human extinction is a real possibility if people continue on their current path. But if they can figure out a way to live sustainably, at least some human civilizations could become quasi-immortal, one researcher says. The challenge is to change the societal outlook to one that is long-term and accounts for humanity's central role in shaping the planet's destiny, instead of one that reacts to immediate crises and thinks in the short term. "For...