Historians and scientists a few millennia from now are likely to see tobacco as one of the major bafflements of our time, suggests Janet Brigham. Why do we smoke so much, even when we know that tobacco kills more than a million of us a year? Two decades ago, smoking was on the decline in the United States. Now the decline has flattened, and smoking appears to be increasing, most ominously among young people. Cigar smoking is on the rise...