Counterfactual Question of the Day

If the ends of our legs were axles and our feet were wheels, how could blood, nutrients, and nerve impulses cross the gap to nurture and direct the moving parts of our natural roller skates?

Stephen Jay Gould, “Kingdoms Without Wheels” in Natural History, Vol. 90, No. 3, 1981, pp. 42–48. Reprinted with postscript in his Hen’s Teeth and Horse’s Toes: Further Reflections in Natural History, W. W. Norton, New York, 1983, pp. 158–165. [PDF]