Barcelona Bipeds

We had a wander around the Port Vell and Barceloneta area of the city this evening. There was lots going on including this group of people dancing to, I am reliably informed, swing music. Everyone else in the area seemed to be on wheels. There were skateboarders, roller skaters, roller bladers, segway riders, bicycles, people on push scooters and even a mobile tapas bar where the patrons sitting at the bar had to cycle the bar along the promenade. (I wasn't fast enough to take a picture). Looking at all this led me to wonder out loud to Marie why evolution has never come up with the wheel for us bipeds. Surely it would be an advantageous survival mechanisim not to mention lots of fun. I suspect the engineering problem of having a fixed axel may be a step to far for genetic mutation. Marie just looked at me in that sort of "I better get you back to the hotel" kind of way.