Today's Marginal Revolution pointed to the following:
1. Culture speeds up human evolution
2. Accelerated adaptive human evolution
3. Human Evolution Has Accelerated
The Scientific American title is a little misleading I think. All discuss the growth in population (and perhaps the adaptation to agricultural life) for the acceleration in the changes in genes. (I may have this wrong since I don't really know my gene from a genome.)
In any case, it reminded me of Greg Bear's Darwin's Radio and it's sequel Darwin's Children. In the book, it was theorized that population pressure and a virus (called SHEVA) causes a genetic mutation that moves humans along to the next step in the evolutionary process.