For many residents of New York City, our bodies are our cars. So rather than engaging in "road rage" against slow or erratic drivers on a highway, New Yorkers descend into "sidewalk rage," paroxysms of fury directed at people who exhibit irrational, obstructive walking behavior on Manhattan's crowded concrete. But is this reaction a sign of mental illness - or could it perhaps reflect an evolutionary adaptation that may have enabled the development of cooperation? (More on Time.com: Five Ways to Stop Stressing) I will admit personally to fits of pique when slow tourists fail to keep to the right,...