As Thiel points out, we travel at the same speeds as we did a half-century ago, whether on the ground or in the air. We rely on the same basic energy sources. Warren Buffett made a $44 billion investment in 2009. It was in a railroad that carries coal.

The Green Revolution improved grain yields by 126 percent from 1950 to 1980, but yields have risen only by 47 percent in the decades since. The big pharmaceutical companies have very few blockbuster drugs in the pipeline. They are slashing their research departments.

If you buy the innovation stagnation thesis, three explanations seem most compelling. First, the double hump nature of the learning curve. When researchers are climbing the first hillside of any problem, they think they can see the top. But once they get there, they realize things are more complicated than they thought. They have to return to fundamentals and climb an even steeper hill ahead.

We have hit the trough phase in all sorts of problems — genetics, energy, research into cancer and Alzheimer’s. Breakthroughs will come, just not as soon as we thought.