For about a decade — a time that Olympic historians may someday classify as “the Michael Phelps era” — I’ve been reading about the unique genetic blessings bestowed upon the greatest swimmer to ever live. Phelps possesses a disproportionately vast wingspan, for example. Double-jointed ankles give his kick unusual range. In a quirk that borders on supernatural, Phelps apparently produces just half the lactic acid of a typical athlete — and since lactic acid causes fatigue, he’s simply better equipped at a biological level to excel in his sport.