As someone who is currently trying to run all 450 miles of the London Underground for charity I think that the greatest challenge of running is mental and not physical. Whilst I take his point we are built better to run long distances - I would love for there to be some analysis on the mental side of running. An animal may not be able to run 26 miles for physical reasons but I firmly believe humans can only run 26 miles if they have cause. If they are inspired. If they are so inspired that giving up is not an option. There is not a hope in hell I could run the distances I am running without being massively inspired by the cause I am running for - that for me is what sets us apart.