Messing up with evolution

Jon had always been intrigued by the way human society had been altered by the evolution.It's enought to say, that the most common concept of sexy comes from the evolution. Women with bigger breasts were able to feed more children, women with widder hips were able to deliver more children, while the ones with smaller could die before delivering the first one. So evolution molded it all in order to make sure the men choosed the most fertile women. But what would have happened if something changed it? What would have happened if evolution choosed the faster, or the smartest, or if, at least, it had been stronger? Jon was asking himself all this questions when he decided to make a wish...