Part of McDougall's point in the book is not just that we CAN run long distances but that, over the long term, it's good for us. For most intensive sports, you can only keep up with them for so long before your body starts to wear and tear. Runners (with proper technique, which is encouraged by minimal footwear) remain healthy and effective until old age.
One of the coolest anecdotes from the book: the average performance of marathon runners increases from age 19 to 27, when it reaches its peak. Performance returns to the 19-year-old level at age 64. That's not true for any other sport. (Citation needed, obviously, but I don't have the book handy.)
The book also gives interesting examples of biological traits we possess, such as bone and muscle configurations, that only appear in animals that run a lot. I'm not saying the book is scientifically rigorous or conclusive, just that there's more to it than appears in this article.
Cyclists have their best years in their late twenties and into their early thirties. Lance was still competitive at the Tour last year, at 37 years old.
Road racing is also very much a long distance sort of sport where endurance is as much if not more important than raw power.
I agree with the premise that we're meant for 'cruising'. I feel best when I go out for long, not particularly fast rides. My favorite thing on a sunny day is to go out for 5 or 6 hours - you feel really good when you're done.
Feet in the Clouds: A Story of Fell Running and Obsession by Richard Askwith is about the British pass time of running up and down very steep peaks, fells and hilltops. He says fell runners usually peak in their mid-thirties to fifties. Youngsters don't have the stamina that a Bob Graham (http://en.wikipedia.org/wiki/Bob_Graham_Round) or Joss Naylor (http://en.wikipedia.org/wiki/Joss_Naylor) have.
Maximizing one's endurance takes years.
Of course there are other factors that affect performance and deteriorate over the years (Force for example) -- which is why endurance athletes peak at their 30ths.
What about martial arts? Not the full-contact ones, I guess, but aikido comes to mind when I think of the one where a person could keep practicing till very old age.
Helio Gracie comes to mind (http://en.wikipedia.org/wiki/Helio_Gracie). Apparently he was still training at the age of 95. Some of the videos of him in his 80s in YouTube show him still to have been a force to be reckoned with.
One of the coolest anecdotes from the book: the average performance of marathon runners increases from age 19 to 27, when it reaches its peak. Performance returns to the 19-year-old level at age 64. That's not true for any other sport. (Citation needed, obviously, but I don't have the book handy.)
The book also gives interesting examples of biological traits we possess, such as bone and muscle configurations, that only appear in animals that run a lot. I'm not saying the book is scientifically rigorous or conclusive, just that there's more to it than appears in this article.