This work contains contributions from behaviour geneticists, evolutionary psychologists, and experts on intelligence, with a general emphasis on exploring the differences and the tensions between evolutionary/psychological approaches and behaviour/genetic approaches. Evolutionary psychology disputes or plays down the existence of general intelligence and emphasises differences between species. However, behaviour genetics emphasises general intelligence as the most fundamental aspect of intelligence and acknowledges differences between individuals of the same species. This is one of the first volumes to specifically try to compare and integrate the very different disciplines of evolutionary psychology and behaviour genetics.