"Research Suggests That Humans Are Becoming More Stupid"

An interesting paper (part 1 and part 2) was published yesterday in the journal Trends in Genetics by Gerald Crabtree that says humans are not as smart as we were thousands of years ago. With agriculture, cities, and less "survival of the fittest," deleterious mutations are surviving and being passed on, often combining with other mutations, producing cascading negative effects. 

Any thoughts on this? It seems in the last few thousand years that there have been some genius minds. But are they recognized because of our technological advances that allow us to spread ideas and cultivate theories? Were there super genius cavemen who just didn't have the advancements to be known today as pioneers of their time? I think its interesting to think of our external advancements as having potentially negative effects on what is going on internally.