The global population is steadily climbing, and by 2050, scientists expect that 10 billion people will call Earth home. This got science writer Charles Mann wondering: How are we going to feed all of those mouths without completely destroying the planet? Mann explores this question in his new book, “The Wizard and the Prophet: Two Remarkable Scientists and their Dueling Visions to Shape Tomorrow’s World.” We talk with him about whether innovation, conservation, or some mixture of the two, that will save humanity.