What if we could use our feet as hands, with the same dexterity. Assume for the purposes of this question that the lower hand is structurally the same as our existing hands. Also assume that our planet's environment, gravity, structure, ecology, flora, fauna and so forth are also otherwise exactly the same.
Would we still walk upright? Would we live in trees or tree-like buildings? Would this have significantly altered history? At which points? How would our society be organized? Our cities? What do you think would be the most significant change?
As the potential answers for these multiple questions may be rather broad, please choose one aspect to focus on, the one you think most important and significant, and answer that specific question-aspect in a few paragraphs.