I understand that abos going without shoes will develop calluses that are a good 1/2 inch thick or more. These also crack so that the effect must be somewhat like the lugs on a good Vibram sole.

I excavated a large ruin at Canyon de Chelly some years ago with excellent preservation, and we found lots of sandals which often had intricate patterns on their soles. Archaeologists in an earlier day often wondered why they put decorative patterns on the soles of the shoes where they would be worn away. As a sometimes rock climber,it seemed rather evident that the patterns would give a good grip when traversing the many vertical routes in the canyon,some of which would rate as 5.8/5.9 on contemporary scales.

I agree that our modern wimpy feet benefit from decent shoes.