Orthopaedic surgeons stand to make a lot of money if Americans decide on running as a commuting method. After all, a mile of running is a mile's worth of bodily wear and tear. Those miles really do add up. I already have a blown left knee from a lifetime of high-speed walking. Ny right leg, which is now favoured is showing its wear and tear with a seemingly permanent pulled muscle. It's a trade off, Do you give your money to a cardiologist or the orthopaedic surgeon as you shred your lower body?

While people in Kenya might have evolved to run marathon-like distances to commute, European type white people have not. That's why we invented cars in the first place. When a runner-commuter can no longer commute what are they supposed to do? Blow themselves up like a Palastinian? When cars are too costly to use, that's what public transit or motorbikes are for. When that gets too expensive, the bicycle will be the method of choice. But something like running 10 miles each way is all but out of the question due to bodily wear and tear. Sure, you'll lose weight that way, but the mileage on the lower body is not worth it. Are you ready to shred your legs to commute?

I doubt evolution has much to do with it, it's a result of lifestyle and not being accustomed to it.  We've only been developing alternatives to walking for a short period of our history.  It's not long enough that we could have evolved away from being able to walk/run.  When people get older they naturally have problems.  It's not just reserved for Europeans by any means.  
Not to mention: why would we go back to walking?  I'm pretty sure a bicycle would still work just fine, and it's probably better for traveling long distances.