While he is known mainly for his ideas on running, given some of the things I've been thinking about recently I thought his bit on sitting was interesting:
Q. People with bad backs often blame evolution for their pain. They say, “My back aches because man was not meant to walk on two feet.” Are they right?
A. If that were true, natural selection would have its toll and we’d be extinct. What is more likely is that many people sit in chairs all day, get no exercise, and thus have weak backs. We did not evolve to sit in chairs all day.