On a rather dull Saturday in November 1984, I found a bombshell in my letterbox. I had received data from a distinguished Dutch researcher and saw immediately that Dutch males had made enormous IQ gains in a single generation. Today similar findings have occurred in almost 30 nations--in every country for which we have data. IQ escalation may not persist, but it has dominated the 20th century. That is enough to create a crisis of confidence. Either the children of today are far brighter than their parents, or at least in some circumstances, IQ tests are not good measures of intelligence. Paradoxes begin to multiply. Only now can we resolve them--and doing so illuminates the nature of intelligence as well as the gulf that separates our minds from those of our ancestors.