A non-diet question here, since a lot of us are interested in other aspects of paleo physiology: I went hiking recently and wore hiking boots while my two buddies had Vibrams. Their feet were pretty beat up afterward, and I read recently about a woman whose brother has broken a toe twice while trail hiking.
At first blush, it's seems that our toes are not well adapted to walking/running outdoors without shoes. There are a lot of sharp rocks, roots, etc. in the wild, and even if you toughened the soles of your feet, I don't see how you could strengthen the small bones in your toes all that much. If we are "meant" to walk barefoot, why it is so easy to stub/fracture/break our toes?