Twelve minutes mile? I walk faster. But If you watch the improvement in the olympic games. The first year you could have won with a time around 12 sec. Some years later you could have won with 11 sec. Now you need around 9.90! That´s a huge improvement. But back then you weren´t actually training. The naturally fast guys were sent to the Olympic games, and when they came home they just continued on with their normal lives.