A tale of three islandsThe world’s population will reach 7 billion at the end of October. Don’t panic IN 1950 the whole population of the earth—2.5 billion—could have squeezed, shoulder to shoulder, onto the Isle of Wight, a 381-square-kilometre rock off southern England. By 1968 John Brunner, a British novelist, observed that the earth's people—by then 3.5 billion—would have required the Isle of