A Biological Dig for the Roots of Language By NICHOLAS WADE Correction Appended Once upon a time, there were very few human languages and perhaps only one, and if so, all of the 6,000 or so languages spoken round the world today must be descended from it. If that family tree of human language could be reconstructed and its branching points dated, a wonderful new window would be opened onto the human past. Yet in the view of many historical linguists, the chances of drawing up such a tree are virtually nil and those who suppose otherwise are chasing a...