We are sure a lot faster than we used to be.

In the space of one century the world record time for running a Marathon dropped from 2:55 to 2:03. That's 30%.

For women, the decline is more dramatic, from 3:40 in 1926 to 2:15 today. That's about 40%.

(Paul Ryan at his personal peak could not have been a competitive female marathon runner in 1926.)

There are all sorts of factors involved. Shoes, who competed, average world nutrition... It isn't that the large change is inexplicable.

But it is a stunning short-term increase in something so basic to our species.

Endurance running is what gave us a big edge over many edible animals that had been forced, by evolutionary hunter/prey arms races, to become low endurance sprinters.


http://en.wikipedia.org/wiki/Marathon_world_record_progression#Marathon_world_record_progression