Stebins did a calculation. How long would it take a species of mouse-sized animals if they were subjected to relentless pressure to get bigger? And I forget the result. But the point was that it was so fast that you wouldn't detect it on the paleontological time scale. It would look like an instantaneous change. So Stebins set the selection pressure at this very low rate. To put it in the noise and then he calculated how long it would take to become elephant-sized. That's right. 12,000 is not that many. People have done whole day in... Did it? And did it as wholeday. You don't know why I understand it